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Multi-Source Classification of Meridiani Planum's Aeolian Landscape Using HiRISE and Opportunity Images Analysis Based on Deep Learning

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The aim of the research was to analyze the possibilities of using deep learning methods for classifying multi-source image data for Mars. It should be emphasized that the main goal of the research was to develop a methodology for integrating image data acquired from orbiters (MRO mission's HIRISE camera) and in situ (Opportunity rover's NAVCAM camera) and to use their combined analytical potential. We used a VGG-16-based network for this study, which is well-characterized in the literature and has been successfully applied in a wide range of applications. The article proposes a methodology for the supervised classification of landforms on Mars. The proposed solution was evaluated using the Meridiani Planum area, utilizing neural network deep learning and was based on multi-source image data. We found that our approach classified aeolian reliefs correctly for more than 94% of the test dataset. The classification accuracy increased to almost 96% when using panoramas developed from Opportunity's images and the derivatives of the digital terrain models used during the classification process. It is possible to broaden the proposed concept of multi-source classification and the customized deep learning system to the analysis of other regions of Mars and to multispectral imaging without losing the generalizability of the solution.
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IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, VOL. 15, 2022 9963
Multisource Classification of Meridiani Planum’s
Aeolian Landscape Using HiRISE and Opportunity
Images Analysis Based on Deep Learning
Kamil Choroma´nski , Joanna Kozakiewicz , Mateusz Sobucki , Magdalena Pilarska-Mazurek ,
and Robert Olszewski
Abstract—The aim of the research was to analyze the possibilities
of using deep learning methods for classifying multisource image
data for Mars. It should be emphasized that the main goal of
the research was to develop a methodology for integrating image
data acquired from orbiters (MRO mission’s HIRISE camera) and
in situ (opportunity rover’s NAVCAM camera) and to use their
combined analytical potential. We used a VGG-16-based network
for this article, which is well-characterized in the literature and
has been successfully applied in a wide range of applications. The
article proposes a methodology for the supervised classification of
landforms on Mars. The proposed solution was evaluated using the
Meridiani Planum area, utilizing neural network deep learning and
was based on multisource image data. We found that our approach
classified aeolian reliefs correctly for more than 94% of the test
dataset. The classification accuracy increased to almost 96% when
using panoramas developed from opportunity’s images and the
derivatives of the digital terrain models used during the classifi-
cation process. It is possible to broaden the proposed concept of
multisource classification and the customized deep learning system
to the analysis of other regions of Mars and to multispectral imaging
without losing the generalizability of the solution.
Index Terms—Deep learning, high resolution imaging science
experiment (HiRISE), mars multisource classification, Meridiani
Planum (MP), MRO, opportunity rover.
I. INTRODUCTION
SINCE aeolian processes play a dominant role on present-
day Mars, the bedforms created due to these processes cover
almost the entire Martian surface. Ripples are one of the most
common aeolian features on Mars; they can be up to 1 m high and
up to several meters wide, and form straight or sinuous ridges
created by the accumulation of small particles (from 100 µm
to 1 mm in diameter). The orientation of these bedforms is
Manuscript received 10 June 2022; revised 16 August 2022 and 11 October
2022; accepted 11 November 2022. Date of publication 21 November 2022;
date of current version 30 November 2022. (Corresponding author: Robert
Olszewski.)
Kamil Choroma´nski, Magdalena Pilarska-Mazurek, and Robert Olszewski
are with the Faculty of Geodesy and Cartography, Warsaw University of
Technology, 00-665 Warsaw, Poland (e-mail: kamil.choromanski@pw.edu.pl;
magdalena.pilarska@pw.edu.pl; robert.olszewski@pw.edu.pl).
Joanna Kozakiewicz is with the Faculty of Physics, Astronomy and Applied
Computer Science, Jagiellonian University, 30-348 Krakow, Poland (e-mail:
j.kozakiewicz@uj.edu.pl).
Mateusz Sobucki is with the Faculty of Geography and Geology, Jagiellonian
University, 30-387 Krakow, Poland (e-mail: mateusz.sobucki@uj.edu.pl).
Digital Object Identifier 10.1109/JSTARS.2022.3222940
perpendicular to the direction of the wind that is responsible for
their creation. On Mars, such bedforms exist as ripple fields, but
can also be found as isolated features [1], [2].
The increasing amount of spaceborne and groundborne data
about Mars’ surface enables large scale terrain relief recognition.
However, this activity is slow because of its manual approach,
and requires automation. To contribute to this process, we
attempted to analyze and classify these forms using machine
learning methods. Because these forms appear over almost the
entire surface of Mars, it is vital to employ automatic techniques
to study their distribution and parameters. To develop such
automatic methods, we started with a region that is well-covered
by both orbiter and in situ data, and which serves as a ground-
truth for analyzing bedforms and terrain. Imaging data from
the rover allows for detailed, high-resolution, analysis of terrain
morphometry, while HIRISE data allows for spatial context
analysis. Multisource data fusion method enables consider the
complementary information between each dataset confirmed,
for example, in the publication [3].
The authors chose an area of Meridiani Planum (MP) that
was investigated by one of two rovers on the Mars exploration
rover (MER) mission [4]. What characterizes this area is its flat
surface, which is interrupted only by impact craters of various
ages [5], [6]. This region’s uniformity favors the development
of automated terrain classification methods.
The opportunity rover explored this region from 2004 to 2018
and took approximately 200 000 images of landforms, rocks,
and sediments. Opportunity traveled more than 40 km across an
area that, from a morphological point of view, can be divided
into two classes of terrain: plains and craters. The surface of the
plains is made of a flat layer of sulfate-rich sandstones partially
covered by loose sediments (made up of sand and gravel). On
these plains, there are vast fields of ripples located on the sand-
gravel covers or directly on the bedrock.
In this research, the objective of the analysis was to automate
the classification process of three geomorphological settings
within the MP area: ripple fields, ripples in bedrock, and sand-
gravel covers. Simultaneously, this classification would enable
a detailed analysis of the distinguishable and unambiguous
geomorphological features within the MP area. In other words,
these three classes would enable the characterization of the
terrain’s surface in terms of the presence or absence of ripples
and sand-gravel covers.
This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/
9964 IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, VOL. 15, 2022
Deep learning methods has strong representation learning
ability and classification ability for spatial big data processing
to automate the process of extracting and classifying landforms,
and therefore enable analysis of image data from both the or-
biter high resolution imaging science experiment (HiRISE) and
the navigational camera on the opportunity rover. The article’s
authors put forward the hypothesis that by using a fusion of
orbiter and in situ data with deep learning, and integrating image
data and the derivatives of the digital terrain models (DTMs),
this would achieve a significant increase in the accuracy of
the automatic classification of the aeolian geomorphological
settings found on Mars. The use of the neural network in the
research work makes it possible to process both image data
and three-dimensional (3-D) models developed from HIRISE
data and image panoramas from the rover. In fact, the image
data from opportunity’s camera panoramas can be processed
into a multidimensional feature vector and analyzed in a joint
classification process together with orthophotos and DTMs from
HIRISE. The approach proposed in this article, and tested for the
MP region, can be used to automate relief classification on Mars.
The issue of Martian aeolian landscape classification has been
the subject of only a few scientific publications using orbiter
orbiter imagery of varying spatial resolution, or using DTM as
the sole data source [9], [12]. This article addresses the subject
of developing a methodology for integrating and processing
multisource photogrammetric data for Mars. The use of stereo
images from the high-resolution HiRISE camera allowed not
only the development of an orthophoto map, but also a DTM
and its derived models: curvature, slopes, topographic position
index (TPI), terrain ruggedness index (TRI), etc. The use of
these models has significantly improved the quality of relief form
classification. The integration of orbiter data with images taken
by the Mars rover’s navigational camera (NAVCAM) allowed us
to develop a holistic methodology for integrating multisensory
data and obtaining satisfactory classification results. The devel-
opment of an innovative method for processing image data from
orbiter and in situ sources allows for synergies and the “enrich-
ment” of spatial data, and provides an important methodological
contribution to fundamental research concerning Mars.
The layout of the article is as follows: Chapter II discusses re-
lated works on the classification of geomorphological landforms
using machine learning methods and DTM creation; while Chap-
ter III discusses the proposed proprietary research methodology
that uses deep learning for processing multisource, spatial big
data to classify aeolian reliefs on Mars. Chapter IV discusses
the conducted research, taking into account both the selection
of source data and their processing methods. This part of the
article also includes a critical discussion of the results. Chapter
V summarizes the research, and proposes a continuation of this
article and the directions it might take.
II. PRELIMINARIES AND RELATED WORKS
The first decade of the 21st century saw the first attempts to au-
tomatically classify Martian landforms [7], [8], [9]. These works
focused on the segmentation of craters from other landforms
using low-resolution DTM data obtained from the Mars orbiter
laser altimeter (MOLA) sensor. Machine learning algorithms,
such as support vector machines were used for the automated
landform segmentation [6]. The increase in the amount and qual-
ity of the imaging data from Mars has led to a better understand-
ing of Mars’ surface. Deep learning algorithms have become
widely used for the automatic detection, classification, and seg-
mentation of landforms on the planet. Such algorithms were used
both for impact [7], [8], [10], [11] and geomorphological (in-
cluding aeolian) forms [12], [13], [14]. Deep learning techniques
have been applied successfully to the most widely used imagery
and elevation data sources collected from Mars: MOLA [7], high
resolution stereo camera (HRSC) [10], context camera (CTX)
[12], and HiRISE [21], [15]. Bickel et al. [16] used convolutional
neural networks (CNNs) to automate rockfall mapping on Mars
and the Moon. The NAVCAM installed on the Mars rovers was
used both for navigation and scientific research. Maki et al. [17]
described the camera’s parameters and possible uses.
There are also works concerning the segmentation and detec-
tion of landforms based on images taken by the Martian rovers.
Wagstaff et al. [18] proposed a neural network for detecting
the content of images taken by the Curiosity rover to provide a
content-based search of such images using a web interface.
There are several studies relating to the use of deep learning
techniques to map geomorphological structures, which is also
the primary goal of this article. Barret et al. [13] are currently
using neural networks for the segmentation of geomorphological
forms that are visible in HiRISE imagery, investigating the
Oxia Planum and Mawrth Vallis areas. Another paper, similar
to the current article, is also by Barret et al. [13], which is
aimed at creating a product that will be helpful to planetary
geomorphologists. Wilhelm et al. [15] introduced a dataset for
machine learning solutions for the geomorphological analysis of
Mars. However, these works did not focus only on aeolian forms,
and did not consider additional data sources such as elevation
models or images from the rovers.
Thus far, only a few studies, by Rothrock et al. [19] and Tao
et al. [20], have used orbiter and in situ data in one pipeline. Their
studies used HiRISE imagery for determining optimal landing
site traversability for future rovers, and in situ data for wheel
slip predictions. However, these two data sources were used
separately. While some studies use DTMs in deep learning pro-
cesses concerning Mars [10], there has been no work combining
image data and elevation models in a deep learning pipeline for
the semantic segmentation of Martian terrain. However, such an
approach has been used on data from Earth [21]. Furthermore,
none of the published works have attempted to use data from both
the rover and the orbiter in a single deep learning segmentation
pipeline. Such attempts relating to Earth have been successful
using orbiter data and street view services for the building type
and land-use classification of urban areas [22], [23], [24]. The
efficient and state-of-the-art practice of semantic segmentation
are described in publications [25], [26].
Combining the rover’s NAVCAM imagery and the orbiter
HiRISE data is a critical step in knowledge acquisition based on
diverse and mutually complementary data. This issue was the
subject of research by Li et al. [27], Di et al. [28], and Alexander
et al. [29].
The quality of the analyses and image classification resulting
from deep learning methods relies heavily on skillful source data
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NSKI et al.: MULTISOURCE CLASSIFICATION OF MERIDIANI PLANUM’S AEOLIAN LANDSCAPE 9965
processing. Our research used information from both the anal-
ysis of HiRISE orbiter data and images from the NAVCAM on
the opportunity rover. HiRISE image processing consists mainly
of image orientation; then the terrain model from the images (or
a stereo pair) is generated. Nonetheless, DTM generation from
Mars images can be challenging, and many scientists are work-
ing on both DTM improvement and DTM evaluation, which can
be a demanding task due to the lack of reference data relating to
Mars (e.g., like the GNSS systems used on Earth). It is possible
to generate DTMs using a photogrammetric workflow. Various
privately developed or commercially available approaches and
software can generate DTMs. Kirk et al. [30] compared various
software packages used for DTM generation: DLR HRSC Team
Pipeline; SOCET SET; and Ames stereo pipeline (ASP). The
most popular open-source software for DTM generation for
Mars is ASP [31]. NASAs ASP is an open-source tool used
for the stereo image processing of data acquired from orbiters
around Earth or other planets [32]. ASP requires the installation
of integrated system for imagers and spectrometers (ISIS), a
digital image processing software package developed by the
United States geological survey for NASA. ASP enables DTMs,
orthoimages, and 3-D models to be generated.
There are also articles in the literature about the comparison
between Mars DTMs generated from different orbiter systems.
Kirk et al. [33] calculated slope angles based on DTMs to assess
the appropriateness of landing places for the Phoenix Mars
Lander. Thus, it is possible to compare DTMs from the HiRISE
images to DTMs from different systems, for example, HRSC or
MOLA measurements.
Another prevalent task found in the scientific literature is
the co-registration of multiresolution DTMs. HiRISE images,
characterized by very high spatial resolution, do not cover Mars
completely. Therefore, much of the research on DTMs for Mars
relates to different approaches that demonstrate the possibilities
of multiresolution DTM co-registration. Lin et al. [34] worked
on the automated co-registration of MOLA, HRSC, and HiRISE
DTMs using surface matching techniques. Wang and Wu [35]
presented a different approach, in which they first co-registered
the CTX and HiRISE images using characteristic points, and
then the DTMs were co-registered based on the new position of
the images.
The issue of the detection and analysis of Martian aeolian
forms has also been the subject of research and publication by
Bandeira et al. [36], Bandeira et al. [37], Carrera et al. [38], and
Va et al. [39].
III. METHODOLOGY
The research aim of this study was twofold: to develop a
methodology for using deep learning methods to automate the
classification of geomorphological settings found in the MP
region; and to perform a quantitative and qualitative analysis of
the results. However, the automation of the image data’s classi-
fication requires that they be preprocessed. It is particularly vital
in the case of Martian data, which lack the unambiguous spatial
reference that GNSS systems provide for Earth. Therefore, the
methodology developed in this work incorporates both elements
that obtained georeferencing for HiRISE and NAVCAM image
data: processing the data into an orthophotomap; DTMs; and the
derivatives of the elevation model developed using orbiter data
(from HiRISE) and the panoramas “seen” by the opportunity
rover (from NAVCAM).
The methodology developed assumes (see Fig. 1).
1) The processing of a stereo pair of HIRISE images into a
DTM and an orthophoto.
2) Obtaining DTM derivative models—curvature models,
TRI, and TPI.
3) The processing of in situ images taken by the NAVCAM
camera into a coherent panorama with an equalized tonal
level and precisely defined spatial orientation.
4) The processing of the above-mentioned image data using
the principal component analysis (PCA) method in order
to reduce the dimensionality of the problem.
5) The combined processing of orbiterdata (orthophotomap,
derived DTM models) and in situ panoramas by a neural
network with a well-defined architecture (VGG-16).
6) The cartographic visualization of the obtained classifica-
tion results together with a comprehensive quantitative and
qualitative evaluation.
Each of the stages required the development of original algo-
rithms (or significant modification of existing methodological
solutions) dedicated to processing image data of a specific
type. For the implementation of most tasks we also developed
their own scripts (mainly in the Python language). It should be
emphasized that due to the specificity of Mars imaging data, an
important problem that is related to the lack of GNSS systems
for this planet, was the issue of the orientation, localization,
and spatial reference of the data. Solving this problem was an
important methodological contribution to the analysis of spatial
data that had no georeferencing.
Fig. 2 presents the general outline of the research methodol-
ogy. The research employed two data sources for all other com-
putations: HiRISE orbiter imagery and the opportunity rover’s
NAVCAM images. A digital orthophotomap with a high spatial
resolution based on the HiRISE imagery and the digital elevation
model of the area of interest, along with derived raster models
(namely TPI, TRI, longitudinal, and cross-sectional curvatures)
were created. Semantic features were extracted from opportu-
nity’s images and interpolated onto the spatial domain. A CNN
model capable of working with many data sources enabled all
the data to be used during the semantic segmentation process.
This chapter focuses on describing the particular stages of the
research.
A. HiRISE Data Preprocessing
The HiRISE data were downloaded from the planetary data
system (PDS) [40] in the form of HiRISE experiment data
records (EDRs) files. Files for eight images were enough to
produce four stereo pairs and to create DTMs that covered the
opportunity’s traverse. The following is a list of the stereo pairs:
ESP_018846_1775 ESP_018701_1775
ESP_051245_1780 ESP_020758_1780
ESP_016644_1780 ESP_037109_1780
PSP_001414_1780 PSP_005423_1780.
9966 IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, VOL. 15, 2022
Fig. 1. Proposed research methodology.
Fig. 2. Outline of the methodology and data used.
The HiRISE data were processed using the NASA ASP (ver-
sion v2.6.2) and ISIS (version 3.6.0) on Ubuntu 18.04 OS.
After downloading, the EDRs were combined into one image.
In the next step, the common areas of each stereo pair of
images (the so-called overlap) were selected automatically to
prepare the images for further processing. Finally, point clouds
from the stereo pairs were generated. From the point clouds,
DTMs in the form of raster files were produced. Later, the
HiRISE images were orthorectified using the DTMs to remove
the influence of terrain height on the images. Following this, the
four orthoimages and the DTMs were mosaicked. The DTM and
orthoimage mosaics were aligned horizontally to the data from
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Fig. 3. Images from the opportunity rover’s NAVCAM (top), and the final panorama (bottom) (the authors’ original work).
the HRSC system, and the DTM mosaic was aligned vertically
to the MOLA DTM. The final image mosaic covered an area
of approximately 87 square km and had a spatial resolution of
27 cm/pixel.
B. NAVCAM Data Preprocessing
The NAVCAM camera was chosen for the in situ investiga-
tion (see Fig. 3). This instrument, designed to provide terrain
context for other instruments, acquired a significant number
of landscape-type images. It also had a larger field of view
(FOV) than the panoramic camera. The navigational camera
was a CCD stereoscopic instrument, with each camera having a
45°x45°FOV and an angular resolution of 0.82 milliradians per
pixel (mrad/pixel). Its depth of field ranged from 0.5 m to infinity.
It was mounted on a mast 1.54 m above the Martian surface and
had a stereo baseline separation of 20 cm [17]. Creating 360°
panoramic views of the local terrain is possible after mosaicking
NAVCAM images.
The approach used in this article is a development and mod-
ification of the methodology proposed by Cao et al. [22]. The
architecture developed by the authors of the current article has
reduced the number of trainable parameters, which yielded better
results for a relatively small dataset.
Also of key importance is the issue of selecting the learning
data. The work of Cao et al. [22] did not took into the account
altitude data (DTM), which was a substantial part of the research
for the current article.
As proposed by Cao et al. [22], to use the rover’s images
in a multisource deep learning process, it was necessary to
transform them into panoramic images representing the in situ
terrain representation around a given point. First, opportunity’s
NAVCAM images, which are available on the NASA PDS, are
at a resolution of 1024×1024, organized by the Martian day
(a sol) on which each image was acquired. Additionally, the
rover’s traverse includes metadata that allows each image to be
associated with the rover’s location and the corresponding posi-
tion of the camera. Because of this information, it is possible to
create a spatially localized panorama for each image-taking site
of the traverse. During the photo stitching process, the histogram
matching technique reduced the radiometric differences between
the images. The final panorama image was created from the
cylinder-projected original images. Areas in which two photos
overlapped were merged by selecting every second pixel of each
image and combining these into a mosaic (see Fig. 3). To ensure
spatial consistency between panoramas, each began in a northern
direction. The resolution of a single panorama was 2048×6992.
Since NAVCAM’s primary purpose was to navigate the rover,
multiple images were not taken at each point of the rover
traverse. On average, 30% of each panorama was covered by
data pixels (i.e., non-NaN pixels). There were 2905 panoramas
created of the study area.
C. In Situ Semantic Feature Extraction
An algorithm proposed by Cao et al. [22] formed the basis for
the workflow for extracting features from the rover’s imagery
data and interpolating them into the orbiter image domain. This
process consisted of two main stages: feature extraction, and
interpolation (see Fig. 4). In the first stage, a pretrained neural
network extracted feature vectors from the input image. A deep
CNN pretrained on the Places365 dataset [41] was used for this
purpose. The Places365 dataset consists of 10 million scene
photographs separated into three macro-classes: indoor; nature;
and urban.
Each panorama image was divided into four equal parts,
facing four different directions. Then, using the pretrained
places-CNN network, a 512-D feature vector was extracted for
9968 IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, VOL. 15, 2022
Fig. 4. In situ semantic feature extraction (the authors’ original work).
each image. Four vectors were concatenated into one 2048-
dimensional vector representing each panorama location. Fi-
nally, PCA was used to reduce the dimensions of the feature
vector to 50. Cao et al. [22] successfully used this number of
representative features.
It was necessary to express the feature vectors representing
the surroundings of opportunity’s traverse in the same domain as
the orbiter data. The Nadaraya–Watson interpolation was used to
interpolate features into the orbiter image domain. This method,
which is a generalization of the inverse distance weighting
method, can model opportunity’s closer panoramas as being
of higher importance, and cut-off, at a predetermined distance,
panoramas that are further away, where the in situ features should
not impact the decision process.
D. Semantic Segmentation Network
An encoder–decoder CNN architecture served as the base
network for the multisource semantic segmentation of the ae-
olian reliefon Mars. Such networks consist of two modules: an
encoder and a decoder. The first one extracts the features from the
input data, and the second one upsamples the extracted features
to reconstruct the original shape of the data. This approach
allows for the pixel-wise segmentation of input raster images.
The use of convolutional layers enables the network to model the
spatial features within the images, which is crucial for achieving
good segmentation results (see Fig. 5).
It should be noted that the combined processing of image
data from HIRISE and panoramas from the opportunity rover
required data preprocessing. The orthophotomap and DMT de-
veloped from the orbital images were registered in the Mar-
tian spatial reference system. The panorama developed from
NAVCAM images was preprocessed based on the rover’s lo-
cation and camera parameters and the angles (horizontal and
vertical) of the imaging direction. The image features were
spatially interpolated.
The encoder part of the network was based on VGG-16
architecture [42]. It consisted of five convolutional blocks. The
first two blocks comprised two convolutional layers followed by
batch normalization [43] and the rectified linear unit activation
function [44]. The subsequent two blocks had three such layers.
A max-pooling layer that reduced the output by two times
followed each block. Instead of a fifth block of VGG-16, two
convolutional layers were used.
The decoder module was also based on VGG-16, but without
the last block, and with upsampling layers (by repeating columns
and rows) instead of max pooling. The decoder also reduced
the number of convolutional filters: the encoder had 17 million
trainable parameters, while the decoder consisted of 1.5 million
such parameters. The reason for introducing the modifications to
the base network architecture (e.g., the reduction in the decoder’s
parameters and changing the final layer of the encoder) was that
the processing of the spatial big data from Mars showed better
performance on test data than the classic, deep neural network
architecture used to process image data collected on Earth.
Finally, a single convolution layer with a spatial resolution
equal to the input image finished the network. The softmax
activation function [45] produced the probability that a given
pixel would be affiliated with one of five classes. A class with a
higher probability was chosen to be valid for each pixel. Fig. 5
shows an overview of the neural network model’s architecture.
We used two data fusion methods for the network architecture.
The digital elevation model’s data was stacked along with orbiter
imagery in the main part of the network and analyzed in the same
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Fig. 5. Architecture of the neural network model (the authors’ original work).
fashion as the spectral bands in the RGB image; thus the input
consisted of three layers. Integrating an additional 50 in situ
feature maps in this way could significantly reduce the impact of
the semantic segmentation from other bands (assuming that the
imagery data is both reliable and the main source of information,
and that other data sources are supplementary). Taking this into
account, we decided to implement an approach introduced by
Cao et al. [22]. The main goal of this approach was to use an
additional encoder to extract semantic features from the maps
and fuse the last layer of each convolutional block with the main
encoder through concatenation with the related feature maps
generated from the orbiter data.
IV. EXPERIMENTS AND ANALYSIS
The research covered the section of MP over which the
opportunity rover had traveled (see Fig. 6). Due to the depth of
the image obtained from the NAVCAM installed on the rover, an
area, limited spatially to a 100 m buffer around the rover’s route,
was selected for analysis. First, the orbiter imagery and DTM
products were cropped to the area of interest. The original data
were also normalized to a value range of 1–255 (with 0 reserved
for “no data” pixels). Elevation models have lower resolution
than orbiter images, so the DTM products were resampled to
match the resolution of the HiRISE images (27 cm/pixel) in such
a way that each pixel of image data corresponded to information
from the nearest pixel of the DTM products. Finally, test data
along with labeling were divided into 256×256 georeferenced
tiles. Information about the position of each tile was necessary to
create matching interpolated terrain features. There were 7,631
tiles created for the entire opportunity traverse buffer area (see
Fig. 6).
The original NAVCAM image dataset contains 51 308 images.
However, these are stereo images; thus, only the images from
the right-side camera were used to create panoramas. Moreover,
images with decayed resolution and those that did not spatially
intersect with an area of interest were also eliminated. This
resulted in 2904 panoramas to be used for feature extraction.
The distribution of the panorama locations was not even: Fig. 6
visualizes this distribution.
A. Training and Test Data
The classification used in the labeling was created based on
the two main terrain relief features found within the research
area. The first was the surface type, either bedrock or loose sed-
iments. The second feature concerned the occurrence of ripples,
which may cover the underlying surface entirely, partially, or
not at all. The resultant combinations of these two main features
produced five potential labeling classes. Two of these classes
were excluded from classification because, in the first case,
no large surfaces were covered solely by bedrock, and second,
loose sediments covered partially by ripples were challenging
to differentiate from loose sediments (see Fig. 7).
The final classifications used in the analysis consisted of:
1) ripple fields;
2) ripples on bedrock;
3) sand-gravel covers; and
4) others, which included craters and linear tectonic forms.
Manually labeled vector data (divided into three classes:
ripple fields—class 101; ripples on bedrock—class 102; and
sand-gravel covers—class 104) served as the basis for training
and testing the CNN model. The authors chose 11 areas for
training purposes and 13 for testing. The process of labeling
9970 IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, VOL. 15, 2022
Fig. 6. Area of interest: The source data and opportunity’s traverse (the authors’ original work).
Fig. 7. Classes of aeolian relief found in the MP area (the authors’ original
work).
and processing the vector data utilized ArcGIS and QGIS soft-
ware environments. A polygon with an associated class number
represented an area corresponding to one class. Fig. 8 shows
an example of a labeled testing area. All labeled areas were
rasterized and tiled along with the corresponding orbiter DTM,
and interpolated in situ features data. As a result, 523 tiles for
each dataset were created for training and 108 for testing. Fig. 9
presents a pixel-wise summary of the training and test datasets
(with the “other” class neglected).
B. Data Augmentation
Because the training dataset was not large enough, it had to
be augmented artificially by creating extra samples using data
augmentation techniques. Many implementations that have had
CHOROMA ´
NSKI et al.: MULTISOURCE CLASSIFICATION OF MERIDIANI PLANUM’S AEOLIAN LANDSCAPE 9971
Fig. 8. Fragment of the labeled data superimposed against the HiRISE data
background (the authors’ original work).
Fig. 9. Summary of the training and test datasets.
limited datasets have employed such techniques successfully
[46]. For each training dataset tile, five augmented tiles were
created by applying the following transformations.
1) Random rotation between 2.5° and 2.5°.
2) Random brightness change between 25% and 25%.
3) Random contrast change between 25% and 25%.
After data augmentation, the entire training dataset consisted
of 3138 tiles per data source.
C. Experiments
The authors conducted six experiments (see Table I) to test
the impact of data source combinations on the final quality of
the model:
TAB L E I
EXPERIMENTS SETUP
1) HiRISE images only—the input data consisted only
of HiRISE images using a single encoder.
2) HiRISE images and TPI/TRI layers—TPI and TRI layers
stacked with HiRISE images using a single encoder.
3) HiRISE images and curvature layers—the use of longi-
tudinal and cross-sectional curvature layers stacked with
HiRISE images using a single encoder.
4) HiRISE images integrated with the in situ feature maps—a
combination of the HiRISE images using the first encoder
with features fused from the in situ feature maps generated
using the second encoder.
5) HiRISE image and TPI/TRI layers integrated with the in
situ feature maps—the same setup as in experiment 4, with
additional TPI and TRI layers stacked with the HiRISE
images.
6) HiRISE image and curvature layers integrated with the
in situ feature maps—the same setup as in experiment 4,
with additional longitudinal and cross-sectional curvature
layers stacked with the HiRISE images.
D. Implementation and Hardware Details
All CNN models were implemented using the Keras library
[47] on top of the TensorFlow framework [48]. The first four
blocks of each encoder were initialized with the corresponding
weights of the VGG-16 network trained on the ImageNet dataset
[49]. Other convolutional layers of the network were initialized
using the He initialization [50]. Each convolutional layer had
l1 and l2 regularizations applied. Cross-entropy was used as a
loss function, and the stochastic gradient descent as a network
optimizer. The learning rate was initially set at 0.01 and then
divided by ten after the 15th, 25th, and 35th epoch. The entire
learning process lasted for 50 epochs. After every training epoch,
data were randomly shuffled to ensure that the model learned
independently of the sample order. The cut-off threshold for the
significance of the in situ features was set to 50 m.
A CENAGIS infrastructure—a computing infrastructure for
conducting spatial big data analyses, created at the Faculty of
Geodesy and Cartography of the Warsaw University of Tech-
nology in 2021—was utilized in conducting the model training
and data preprocessing. Computations were conducted using a
separated Docker [51] environment with access to 128 Gigabytes
9972 IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, VOL. 15, 2022
of memory, 8 Intel Xeon Silver 4216 CPU cores, and 1 NVIDIA
TeslaT4GPU.
E. Evaluation Metrics
The authors used global and per-class evaluation metrics to
assess the results: overall pixel accuracy; per-class pixel ac-
curacy; per-class precision; per-class recall; and per-class F1
score. Additionally, a normalized confusion matrix for each
experiment was created as follows.
1) Overall pixel accuracy
acc =tr (CM)
N(1)
where tr is the trace of the matrix, CM is the confusion matrix,
and Nis the number of pixels in all classes
1) Per-class accuracy
accc=CMcc
(c).(2)
2) Per-class precision
pc=CMcc
n
j=1 CMcj
.(3)
3) Per-class recall
rc=CMcc
n
j=1 CMjc
(4)
where crepresents the index of a given class in the confusion
matrix, nis the number of all classes, CMij is the ith row and
the jth column element in the confusion matrix, and (c)is the
number of elements in class c [for (2)–(4)].
The per-class F1 score takes precision and recall metrics into
account
F1=
2pcrc
pc+rc
.(5)
V. R ESULTS AND DISCUSSION
The conducted experiments showed that using the HiRISE
data and advanced machine learning methods that utilize a
deep learning approach, produces over 94% accuracy in the
automatic classification of aeolian reliefin the MP region. One
should emphasize that, due to the spatial data processing, the
training and validation dataset analysis is a long drawn-out
process requiring specialized computing infrastructure based on
graphics processors.
Using data fusion, i.e., the combined use of orbiter imaging
and elevation data (DTM and its derivative TPI and TRI models),
fosters further classification accuracy. Using an even broader
scope of data, i.e., the fusion of HiRISE orbiter data (image
and elevation data) and in situ data (panoramas recorded by
opportunity’s NAVCAM), produces the best results.
It is noteworthy that both the quantitative analysis (see
Table II) and the qualitative analysis (see Fig. 10) were essential
for evaluating the results that were obtained. A relatively small
difference (amounting to 1%) in the accuracy of the results
(95.94% for set 5 and 94.90% for Set 2) does not fully reflect
TAB L E I I
EXPERIMENT ACCURACY
Fig. 10. Results of data classification: Set 2 (left) and set 5 (right).
the quality of the final classification. The fusion of orbiter and in
situ data enables a “smooth” image to be produced of individual
geomorphological settings (see Fig. 10), compared with the
results for a different set of source data, for which the edges
of feature classes were sharper.
When analyzing the results, one should also emphasize that
they depend not only on the amount of source data and the meth-
ods used for their preprocessing, the neural network architecture,
or the parameterization of the deep learning process, but also
on the quality of the vector data used in the machine learning
process. The preparation of a training data set requires that the
data be divided into object classes (this approach employed three
such classes), and a manual process is used for determining the
individual divisions. The boundary between individual classes,
CHOROMA ´
NSKI et al.: MULTISOURCE CLASSIFICATION OF MERIDIANI PLANUM’S AEOLIAN LANDSCAPE 9973
TABLE III
RESULTS
for example, ripple fields and ripples on bedrock, is blurry and
may differ depending on the observer’s knowledge, experience,
and intuition. The research used training data that was selected
manually by two independent observers to minimize this prob-
lem. The same method was used to determine the validation and
testing data.
It should also be noted that the specificity of Mars and its land-
scape both play an essential role in automating the spatial data
classification process. The conducted experiments showed that
using a deeper and more complex neural network architecture
(SegNet [52]) did not produce better quantitative results, and
resulted in a qualitatively worse semantic segmentation effect.
The experiments also showed that, in the case of the SegNet
tests, there was no improvement in the segmentation quality
when using additional data sources (i.e., in situ images). This
stems from the specificity of the aeolian landforms in the MP
area. Obtaining these results (see Table III) required a series of
numerical experiments applying many different modifications
to the neural network architecture.
Achieved accuracies are on the level of 1% in favor of a
fused approach, which is not a large improvement in quantitative
assessment; however, the difference is visible in the qualitative
assessment of the results (see Fig. 10).
The main objective of the research was to test the impact
of using combinations of different spatial data types on the
performance of the network. The network used in this research
was the VGG-16—the basis of this architecture is a known and
well tested solution. However, in the future, it will be necessary
to investigate the performance of the built system using another,
more efficient architecture (such as EfficentNet [53] or CoAtNet
[54]), which may translate into better results in less time. This
task will require the development of an optimal methodology
for connecting the intermediate layers of each encoder, taking
into account the specifics of the network architecture used.
This issue requires further research, as the analysis and
classification of aeolian features on Mars is of interest to many
research teams [55].
VI. CONCLUSION
This article has shown that, for the analysis of multisource
data that describes the surface of Mars, selecting the appropriate
methodology and geoinformation tools is crucial. Because the
HiRISE camera and the opportunity rover have collected spatial
big data over a number of years, the processing of this data
requires machine learning methods that adopt a deep learning
approach. Developing a methodology for data analysis and clas-
sification also requires defining the object classes distinguished
in the automatic classification process. This article assumes
that ripple fields, ripples on bedrock, and sand-gravel cover are
intrinsic to the MP region. Differentiating these object classes
concerns the structure and distribution of aeolian reliefobserved
in this region of Mars. However, the developed approach is so
universal that, without inference accuracy loss, it is possible to
either generalize or refine the distinguished classes, or add new
ones with morphological features that are characteristic for other
areas of the planet.
It is important to note that to obtain satisfactory scientific
and cognitive classification results, the fusion of source data,
their preprocessing, and the appropriate choice of deep neural
network architecture are essential. Using both the image data
from the orbiter and the data obtained in situ by the rover in the
machine learning process improved our results. When analyzing
the results, one should also note that using a broad range of
source data and the derivatives of DTMs enables a “smooth”
image to be achieved, made up of individual subdivisions,
which is analogous to manual classification. Selecting the neural
network architecture also plays a vital role in this process. The
deep learning network models that we used increase the rate of
correct classification and—similar to data fusion—contribute to
the regularization of the shapes of individual features.
The results make it possible to develop a map of the domi-
nant land cover types for the opportunity rover’s traverse; the
developed methodology is also the first step toward developing
a comprehensive, multilayer geomorphological map of Mars.
9974 IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, VOL. 15, 2022
According to the analyses, there are complex, modular geomor-
phological features in many places that may be interpreted as
multilayer formations. The development of the research method-
ology proposed in this article will enable the classification of
modular features and serve as a basis for developing tools that
automate the classification process of land cover types and in-
dividual objects such as ripples. An in-depth numerical analysis
of the morphometric parameters of individual forms and the
determination of their features, such as spacing, morphome-
try and morphology, and crest direction, constitutes an initial
step towards inferring, from static data analysis (e.g., image
data), the lengthy morphodynamic processes that create aeolian
landforms.
This article analyzes classification capabilities based on a
DTM developed from HIRISE data and panoramas obtained
from the opportunity rover. Further work will focus on the use
of the 3-D models developed from the opportunity rover’s stereo
images, as well as comparing the interpretability of the terrain
model obtained from orbiter data (HIRISE) and from the rover
(opportunity).
Further research in this area will deal with the methodology
we have developed in order to analyze the data collected by the
Perseverance rover’s significantly greater number of cameras,
and the image data obtained by the Ingenuity drone. Using the
data collected during these missions will enable the development
of a digital elevation and terrain model that will have an order
of magnitude greater resolution than that of the opportunity
rover, thus enabling machine learning methods to automate the
classification of specific morphological features on Mars.
ACKNOWLEDGMENT
This project was funded by POB Research Centre Cyberse-
curity and Data Science of Warsaw University of Technology
within the Excellence Initiative Program—Research University
(ID-UB), and the Anthropocene Priority Research Area budget
under the program “Excellence Initiative—Research Univer-
sity” at the Jagiellonian University.
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Kamil Choroma´nski received the B.Sc. degree in
geoinformatics in 2019 and the M.Sc. degree in
geodesy and Cartography in 2020 from Warsaw Uni-
versity of Technology, Warsaw, Poland, where he is
currently working toward Ph.D. degree.
He is a Machine Learning Specialist with SkySnap
company, Warsaw, Poland. His main areas of exper-
tise are spatial big data and spatial applications of
deep machine learning algorithms related mainly to
computer vision.
Joanna Kozakiewicz receivedthe Ph.D. degree in as-
tronomy from the Jagiellonian University in Krakow,
Krakow, Poland, in 2016, where she is currently work-
ing as an Astronomer with the Jagiellonian Univer-
sity, Krakow, Poland.
Her research focuses on planetary science. She
conducts projects on aeolian processes, landforms,
and sediments on Mars, geomorphological mapping
of Mars, and developing computer vision tools for
planetary science.
Mateusz Sobucki received the M.S. degree in
geodesy and cartography from the AGH University
of Science and Technology, Krakow, Poland, in 2006,
and the B.S. degree in physical geography in 2008
from the Jagiellonian University, Krakow, Poland,
where he is currently working toward the Ph.D. degree
in fluvial geomorphology.
He is currently a Geomorphologist with the Insti-
tute of Geography and Spatial Management, Jagiel-
lonian University, Kraków, Poland. His present re-
search interests include dynamic geomorphology, ge-
omorphometry and planetary science.
Magdalena Pilarska-Mazurek received the Ph.D.
degree in geodesy and cartography from the Warsaw
University of Technology, Warsaw, Poland, in 2021.
Since 2016, she has been a Research-Teaching
Assistant with the Department of Photogrammetry,
Remote Sensing, and Spatial Information Systems,
Faculty of Geodesy and Cartography. Her research
interests include UAV photogrammetry and aerial
and UAV lidar. Her research is the processing and
analyzing of aerial and UAV lidar and the application
of UAV data in different fields.
Dr. Pilarska-Mazurek is a Member of the Polish Society for Photogrammetry
and Remote Sensing.
Robert Olszewski received the Doctorate degree in
geodesy and cartography from Warsaw University of
Technology, Warszawa, Poland, in 2001.
He conducts research on the modeling of spatial
information or, more precisely, the extraction and
acquisition of spatial information using artificial in-
telligence methods, as well as on the smart city con-
cept, cartographic generalization, geostatistics, gam-
ification, and social geoparticipation. The results of
many years of his research work have been published
in several monographs and more than one hundred
papers. Since 2011, he has been a Professor with the Faculty of Geodesy and
Cartography, Warsaw University of Technology, Warsaw, Poland. Since 2015,
he has been the Head of the Chair of Cartography. He works with businesses
as well as government and local- government entities in the implementation of
R&D projects and commercialization of interdisciplinary research in the field
of geoinformation and spatial data mining.
... As aeolian ripples are common landforms on Mars, some automatic techniques are necessary to investigate their parameters and distribution. The methodology proposed by Choromański et al. [34] for the supervised classification of terrain on Mars takes advantage of integrating multiple data sources: the NAVCAM rover data from the Opportunity mission [35] and the imagery data from HiRISE [36]. The solution was evaluated using deep learning techniques (e.g., convolutional neural networks). ...
... The solution was evaluated using deep learning techniques (e.g., convolutional neural networks). Very good semantic segmentation was achieved with an overall test dataset accuracy of more than 94% using only the orbital data, nearly 95% when the information from the digital terrain model was added, and close to 96% using all available data [34]. ...
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We give an overview of Polish activities in planetary physics, based on contributions presented at the National Mars Science Seminars and the Planetary Science Conference held at the Jagiellonian University in Kraków since 2019. During the five editions of the conference, about 50 presentations were discussed showing how robust and important the role of the Polish scientific community in planetary science is.
... It achieved an overall accuracy of 94.38% with only the use of image orbital data, 94.90% adding terrain information, and 95.94% using all available data. The entire study was published in Choromański et al. (2022). ...
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Recently, China and the United States have achieved remarkable success in aerospace science and technology over the years. Space has become another field of competition in the technological advancement of various countries. Through space missions, space tourism, moon and Mars exploration, China and the United States can demonstrate the sophistication of their technologies to the public and audiences around the world. Despite the competitiveness between the big countries, space missions and deep space exploration and exploitation have provided a lot of deep and orbital space information that is beneficial not only for the next space mission but also for enhancing technological development for other domestic uses. Therefore, space industrial information integration (III), or Space III, connecting IoT to form the Internet of Planets, is critically important for deep space explorations. However, few articles have reviewed the existing technologies of space. We are one of the few groups to perform an extensive review, research the space explorations and divide the space information integration systematically based on the information architecture and technologies in the space industries. In this paper, we propose that III can be divided into three different architectures: data, technology, and application, whereas space technology can be divided into six areas. This review is important not only in formulating research in technological integration but also in determining the proposed architecture to facilitate a further extension of applications to large-scale and complex problems in the space industries in the future.
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The wind interacts with the surface of Mars, forming aeolian landforms. The orientation of these landforms informs us about the formative wind directions. The observations of the orientation of aeolian landforms on Meridiani Planum between Mars years 26 and 38 indicated that there is a seasonality of formative wind directions in this region. The studied landforms were shaped by a predominant SE wind during summer, while during winter several wind directions played a role in their formation. Throughout the Mars year, the most formative were the NW winds. The presence of dark wind streaks oriented toward the west during winter indicates that E winds occur in this season on Meridiani Planum, as previously predicted by numerical simulations. It was also found that aeolian deflation led to complete erosion of smaller dunes, and that the relatively strong deflation was responsible for the scarcity of fine-grained ripples on Meridiani Planum. In this region, fine-grained ripples were found only in a few locations, and they were mainly small bedforms with wavelengths up to several centimeters.
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Contrast to the global forest, few trees live in cities but contribute significantly to urban environment and human health. However, the classical satellite-derived land cover/forest cover products with limited resolution are not fine enough for the identification of urban tree, which is usually appeared in small size and intersected with infrastructure. To relieve the dilemma, this study developed an urban tree specific sub-pixel mapping (SPM) architecture with deep learning approach, which aimed to generate 2m fine-scale urban tree cover product from 10 m Sentinel-2 images for large-scale area of 34 metropolises in China. The proposed approach has remarkable reconstruction ability for delineating the contextual characteristic of the urban tree patterns, and reliable generalization ability to large-scale area. In addition, this study creates a large-volume urban tree cover dataset (UTCD) with 0.13 billion urban tree samples at 2 m resolution, which fills the deficiency of standard dataset in urban tree cover research field. Quantitative analysis of our products was conducted on two typical study sites of Beijing and Wuhan. The results show that our products recover averagely more than 58.72% of urban tree covers that have been underestimated in the existing land cover/forest cover products, and outperforms the state-of-the-art approach both visually and quantitatively, by averagely 11.31% improvement in overall accuracy. From our annual products during 2016–2020, we found an evolution characteristic of urban tree cover: it is more stable in developed cities like Beijing, while more fluctuated in developing cities like Wuhan, and the alteration are usually concentrated at the outer-ring of downtown, which may be caused by the municipal planning and the land development of real estate industry.
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We have used high-resolution digital terrain models (DTMs) of two rover landing sites based on mosaicked images from the High-Resolution Imaging Science Experiment (HiRISE) camera as a reference to evaluate DTMs based on High-Resolution Stereo Camera (HRSC) and Context Camera (CTX) images. The Next-Generation Automatic Terrain Extraction (NGATE) matcher in the SOCET SET and GXP® commercial photogrammetric systems produces DTMs with good (small) horizontal resolution but large vertical error. Somewhat surprisingly, results for NGATE are terrain dependent, with poorer resolution and smaller errors on smoother surfaces. Multiple approaches to smoothing the NGATE DTMs give similar tradeoffs between resolution and error; a 5 × 5 lowpass filter is near optimal in terms of both combined resolution-error performance and local slope estimation. Smoothing with an area-based matcher, the standard processing for U.S. Geological Survey planetary DTMs, yields similar errors to the 5 × 5 filter at slightly worse resolution. DTMs from the HRSC team processing pipeline fall within this same trade space but are less sensitive to terrain roughness. DTMs produced with the Ames Stereo Pipeline also fall in this space at resolutions intermediate between NGATE and the team pipeline. Considered individually, resolution and error each varied by approximately a factor of 2. Matching errors were 0.2–0.5 pixels but most results fell in the 0.2–0.3 pixel range that has been stated as a rule of thumb in multiple prior studies. Horizontal resolutions of 10–20 image pixels were found, consistently greater than the 3–5 pixel spacing generally used for stereo DTM production. Resolution and precision were inversely correlated; their product varied by ≤20% (4–5 pixels squared). Refinement of the stereo DTM by photoclinometry can yield quantitative improvement in resolution (more than a factor of 2), provided that albedo variations over distances smaller than the stereo DTM resolution are not too severe. We offer specific guidance for both producers and users of planetary stereo DTMs, based on our results.
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Mapping planetary surfaces is an intricate task that forms the basis for many geologic, geomorphologic, and geographic studies of planetary bodies. In this work, we present a method to automate a specific type of planetary mapping, geomorphic mapping, taking machine learning as a basis. Additionally, we introduce a novel dataset, termed DoMars16k, which contains 16,150 samples of fifteen different landforms commonly found on the Martian surface. We use a convolutional neural network to establish a relation between Mars Reconnaissance Orbiter Context Camera images and the landforms of the dataset. Afterwards, we employ a sliding-window approach in conjunction with a Markov Random field smoothing to create maps in a weakly supervised fashion. Finally, we provide encouraging results and carry out automated geomorphological analyses of Jezero crater, the Mars2020 landing site, and Oxia Planum, the prospective ExoMars landing site.
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Transverse aeolian ridges (TARs) are unusual bedforms on the surface of Mars. TARs are common but sparse on Mars; TAR fields are small, rarely continuous, and scattered, making manual mapping impractical. There have been many efforts to automatically classify the Martian surface, but they have never explicitly located TARs successfully. Here, we present a simple adaptation of the off-the-shelf neural network RetinaNet that is designed to identify the presence of TARs at a 50-m scale. Once trained, the network was able to identify TARs with high precision (92.9%). Our model also shows promising results for applications to other surficial features like ripples and polygonal terrain. In the future, we hope to apply this model more broadly and generate a large database of TAR distributions on Mars.
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NASA has acquired more than 22 million images from the planet Mars. To help users find images of interest, we developed a content-based search capability for Mars rover surface images and Mars orbital images. We started with the AlexNet convolutional neural network, which was trained on Earth images, and used transfer learning to adapt the network for use with Mars images. We report on our deployment of these classifiers within the PDS Imaging Atlas, a publicly accessible web interface, to enable the first content-based image search for NASA’s Mars images.
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In this investigation a deep learning terrain classification system, the “Novelty or Anomaly Hunter – HiRISE” (NOAH-H), was used to classify High Resolution Imaging Science Experiment (HiRISE) images of Oxia Planum and Mawrth Vallis. A set of ontological classes was developed that covered the variety of surface textures and aeolian bedforms present at both sites. Labelled type-examples of these classes were used to train a Deep Neural Network (DNN) to perform semantic segmentation in order to identify these classes in further HiRISE images. This contribution discusses the methods and results of the study from a geomorphologists perspective, providing a case study applying machine learning to a landscape classification task. Our aim is to highlight considerations about how to compile training datasets, select ontological classes, and understand what such systems can and cannot do. We highlight issues that arise when adapting a traditional planetary mapping workflow to the production of training data. We discuss both the pixel scale accuracy of the model, and how qualitative factors can influence the reliability and usability of the output. We conclude that “landscape level” reliability is critical for the use of the output raster by humans. The output can often be more useful than pixel scale accuracy statistics would suggest, however the product must be treated with caution, and not considered a final arbiter of geological origin. A good understanding of how and why the model classifies different landscape features is vital to interpreting it reliably. When used appropriately the classified raster provides a good indication of the prevalence and distribution of different terrain types, and informs our understanding of the study areas. We thus conclude that it is fit for purpose, and suitable for use in further work.
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This paper describes advances in an automatic approach for the detection of sand dunes of Mars, based on supervised learning techniques. A set of features (gradient histogram) is extracted from the remotely sensed images and two classifiers (Support Vector Machine and Random Forests) are trained from this data. The evaluation is conducted on 230 MOC-NA images (spatial resolution between 1Á45 and 6Á80 m/pixel) leading to about 89% of correct detections. A detailed analysis of the detection results (dune/non-dune) is performed by dune type or bulk shape, confirming high performances independently of the way the dataset is analysed. This demonstrates the robustness and adequacy of the automated approach to deal with the large variety of aeolian structures present on the surface of Mars.