Available via license: CC BY 4.0
Content may be subject to copyright.
ISRAELI NATIONAL AERIAL DATA CAPTURING STANDARD FOR GENERATION
OF DIGITAL GEOSPATIAL PRODUCTS AT NATIONAL SCALE
aEran Keinan, aNoam Shwarts*, aOfer Siman Tov, aHagi Ronen, bRonen Regev
a Survey of Israel, Lincoln 1, Tel-Aviv, 61141- (eran, noam, oferst, hagi)@ mapi.gov.il
b ronen.regev@gmail.com (former Survey of Israel Director General)
Commission II, WG II/1
KEY WORDS: NMCA, digital photogrammetry, ortho imagery, GCP, GSD, DSM, DTM, point cloud.
ABSTRACT:
Digital camera systems are a key component in the production of reliable, geometrically accurate, high-resolution geospatial products
in a national scale. These systems have replaced film imaging in photogrammetric data capturing. Today, we are witnessing a
proliferation of imaging sensors, collecting images in different ground resolutions, spectral bands, swath sizes, radiometric
characteristics and accuracies being carried on varied mobile platforms. In addition, these imaging sensors combined with navigational
tools (such as GPS and IMU), active sensors such as laser scanning and powerful processing tools, to obtain high quality geospatial
products. The quality of these geospatial products based on the utilization of calibrated, high-quality digital camera systems.
The new Survey of Israel (SOI) regulations specify the quality requirements for each geospatial product including maps at different
scales and for different purposes, elevation models, ortho imagery etc. In addition, the regulations require that digital camera systems
utilized for mapping purposes should be certified, using a rigorous mapping systems certification and validation process, which are
specified in the SOI Director General Instructions (DGI).
In 2019 the SOI has updated the camera certification and validation procedure and published a new national aerial capturing standard
for digital geospatial products as a basis for the public bid in three main fields:
1. Aerial data capturing including ground control points (GCP) measurements and aerial triangulation.
2. Ortho imagery in several ground resolution distance (GSD) and several projections.
3. Digital Elevation models including: points clouds, Digital Surface Model (DSM) and Digital Terrain Model (DTM).
This article provides the details of the Israeli Directive for camera certification and Standard for digital geospatial products including
the main technical requirements of the public bid that was carried out.
1. INTRODUCTION
The ASPRS publish new standard (ASPRS et al., 2014) that
addresses geo-location accuracies of geospatial products with no
intention to cover classification accuracy of thematic maps. The
standard does not specify the best practices or methodologies
needed to meet the accuracy thresholds. The ASPRS standard is
intended to use by geospatial data providers and users to specify
the positional accuracy requirements for final geospatial
products.
Land Information of New Zealand (LINZ) also publish a
Standard for nationwide Orthophoto capturing addressing
capturing standards, product delivery guidelines and quality
assurance standards for Orthophoto products (LINZ et al., 2013)
but it didn’t address the means to achieve the accuracy goals.
The Survey of Israel Regulations directivities include new
definitions for mapping products, new requirements for quality
(accuracy and content) of these products and an update of the
procedures, methods and technologies. These regulations also
provide the details for utilization of digital mapping platforms
including the validation, calibration and certifications of these
platforms (Felus et al., 2016). In 2019 the SOI published a new
Director General Instruction refining the process of mapping
systems certification and validation.
* Corresponding
It is agreed by all, that the most important topic is to define the
accuracy of the final products. However, in the perspective of
National Mapping and Cadaster Authority (NMCA) it is very
important to define a clear, reliable and practical standard as a
basis for a public bid in cases that the NMCA’s use the
global\local market to generate the geospatial products.
The objectives of the standard are:
1. Correlate with digital sensors in order to generate geospatial
products.
2. Generate eco system based on the professional capacities of
the local market and the governmental and public needs.
3. Support dissemination of up to date geospatial products
(Ortho imagery, Digital Elevation models etc.) annually.
This article presents a practical approach taken in Israel. Section
2 describe the main regulations and the new Director General
Instruction (DGI) that influence the standard. Section 3 describe
the main topics of the Israeli National Standard for national aerial
data acquisition and geospatial products. Section 4 concludes the
report with a description of the public bid carried out, and further
work to be carried out on the topic.
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLIII-B2-2022
XXIV ISPRS Congress (2022 edition), 6–11 June 2022, Nice, France
This contribution has been peer-reviewed.
https://doi.org/10.5194/isprs-archives-XLIII-B2-2022-65-2022 | © Author(s) 2022. CC BY 4.0 License.
65
2. MAPPING REGULATIONS AND DIRECTOR
GENERAL IN ISRAEL
Mapping and surveying procedures and technologies are
regulated in Israel since 1929 when the British Mandate enacted
the Survey Ordinance. This Ordinance necessitate the publication
of the Survey Regulations as the official document that defines
and regulates the surveying work and the publication of the DGI
that provide the technical details about the methodology and
technologies (Felus et al, 2016).
As mentioned above, this section describe the main regulations
and DGI in the field of geo information and mainly in the field of
digital photogrammetry and geospatial products.
2.1 Digital Camera Certification
The certification process was describe in details at the National
guidelines for digital camera systems certification by Felus et al.
(2016). In 2019 he SOI established and maintain a new
certification test field in Netanya, in order to check and certify
digital camera systems. The test field, consists of more than 200
ground control points measured in very high accuracy, for the
certification process. Figure (1) describe the process and present
the test field:
Figure (1a): Certification process
Figure (1b): Certification test field, Netanya
The DGI ranking digital camera systems for mapping is based on
the Survey Regulation requirements. Based on the main
characteristics, the ranking determination is implemented to the
digital camera system as describe in Table (1):
Criteria\Ranking
A
B
C
D
aircraft
airplane
airplane
airplane
UAV
gyro stabilizer
FMC
max radial
distortion µm
6
12
24
40
IMU
GNSS
DGPS
GPS
Image format
large
medium
small
small
Table 1: Ranking and Criteria of Digital Aerial Systems
The ranking of the digital camera system done by all accumulate
criteria’s. Furthermore, the digital camera system ranking is not
the tool to achieve the final accuracy. In order to deal with the
accuracy of the product each digital camera system was checked
and certified, i.e.: a digital camera system that its ranking defined
as B is also certify to mapping in high accuracy, the same as
another system with A ranking. More details on the accuracy of
the final products and the SOI regulations were already describe
by Felus et al. (2013).
2.2 Density and Accuracy of GCP and AT Accuracy
The main factors that directly influence the accuracy of the
geospatial products produced by digital camera systems for
engineering purposes (i.e. construction permit maps) are:
1. The accuracy of the ground control points.
2. The density of the ground control points.
3. The accuracy of the Aerial Triangulation solution.
This sub section will describe the DGI topics in order to assure
that the quality of the final products meets the SOI regulations.
In order to achieve the accuracy the DGI use the assumption that
the accuracy of the ground control points, in terms of RMSE,
should be half of the final accuracy.
The ASPRS already refer to distribution of GCP (ASPRS et al.,
2004) The DGI use the recommendation of the ASPRS as a basis
for the determination of the amount and distribution of the ground
control points define as follow:
1. Each GCP should be located only in a stereoscopic
coverage.
2. The edges of the block should be register by GCP.
3. In case of digital camera system with dual frequency
DGPS:
a. Each strip in the edged of the block should be register
by GCP every sixth image.
b. In transition strips, every sixth image should be register
by GCP.
4. In case of digital camera system with single frequency
GPS:
a. Each strip in the edged of the block should be register
by GCP every fourth image.
b. In transition strips, every fourth image should be
register by GCP.
Figure (2) illustrate the principles of the amount and distribution
of the GCP’s:
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLIII-B2-2022
XXIV ISPRS Congress (2022 edition), 6–11 June 2022, Nice, France
This contribution has been peer-reviewed.
https://doi.org/10.5194/isprs-archives-XLIII-B2-2022-65-2022 | © Author(s) 2022. CC BY 4.0 License.
66
Figure (2a): distribution of GCP for dual frequency GPS
Figure (2b): distribution of GCP for single frequency GPS
As mentioned above the accuracy of the AT is also a key
component for assure the final quality of the final geospatial
product. Table (2) describe the accuracy levels, GSD and the
RMSE of the GCP and AT (see Annex 1).
3. MAIN TOPICS ISRAELI NATIONAL AERIAL DATA
CAPTURING STANDART FOR GENERATION OF
DIGITAL GEOSPATIAL PRODUCTS
Israel is a small country in terms of size (~28,000 km2) but
characterized by rapid development and construction. These
changes lead to demand from the Israeli Governmental Inter
Office Committee for GIS to produce geospatial products (i.e.
ortho imagery) in a national scale annually.
This demand lead us to promote a new standard, which utilize for
the public bid. The standard divided into 3 main chapters:
1. Chapter A – describe the definition for digital camera
systems, aerial data capturing, GCP establishment and
measuring, AT solution and quality control.
2. Chapter B - describe the definition for ortho imagery
generation (geometric and radiometric) and quality
control.
3. Chapter C - describe the definition for elevation models
generation and quality control.
The next sections will describe the main topics of each chapter.
3.1 Chapter A
3.1.1 Digital Camera Systems
The camera system must be categorized level A with accuracy
level 5 approved by the DGI. The digital camera system must be
mounted on a 3 execs stabilizer and have panchromatic and multi
spectral channels (RGB & NIR)
3.1.2 Aerial Data Capturing
The Aerial data capturing must be performed with clear sky (no
clouds or clouds haze) during the mounts March to August and
between the hours 10:30- 14:30 depending the month. Capturing
months and hours were set by the principle of keeping the sun
angle at 45 degrees from the horizon or higher to achieve
minimum shadow effect.
The maximal allowed exposers angles are: for roll and pitch,
for heading.
Table (3) describe the overlap percentages*:
Area type
Forward overlap
Side overlap
Rural
60%
30%
Urban
80%
40%
Dense Urban
80%
60%
Table 3: Forward and side overlap
*One of the Standard annexes is a map of Urban and Dense
Urban areas to be captured at higher overlap. The map is also
provided in a form of a SHP file.
3.1.3 Ground Control Points
The amount of ground control points and the distribution must be
according to the DGI as follow:
a. Each strip in the edged of the block should be register by
GCP every sixth image.
b. In transition strips, every sixth image should be register by
GCP.
The ground control points must be visible and stable manmade
objects lower than 1 meter from the ground (preferably road
markings, edge of pavement, edge of manholes etc.) In open
areas, the centre of small bushes can be used if approved in
advanced.
3.1.4 Aerial Triangulation
In order to achieve continuity and equality the aerial triangulation
must be performed in blocks as big as possible (at least 500 km2)
and tie points and ground control points from surrounding blocks
must be used.
The tie point’s distribution will be meet Van Groover pattern and
an automatic algorithm will clean any abnormal values.
Aerial triangulation results must be within the RMSE values
approved by the DGI (see table 2 at Annex 1).
3.1.5 Quality Control
As mentioned earlier, the quality of the aerial imagery acquisition
and the accuracy of the aerial triangulation play a key role in
determining the final accuracy of imagery derived mapping
products and therefor, the main purpose of this stage is assure that
the Orthophoto and height elevation models are produced
accurately and with no mistakes.
Most of the procedures are done automatically, running a series
of tests set to validate the products are according to the standard.
Table (4) describe the main testing sets:
Subject
Testing method
Procedure
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLIII-B2-2022
XXIV ISPRS Congress (2022 edition), 6–11 June 2022, Nice, France
This contribution has been peer-reviewed.
https://doi.org/10.5194/isprs-archives-XLIII-B2-2022-65-2022 | © Author(s) 2022. CC BY 4.0 License.
67
Image quality
manually
No clouds or clouds
shadows, No blurred
images
Capturing hours
automatically
Hours defined in the
standard by month
Overlap
automatically
Checking the overlap
with reference to the
urban/dense urban
areas
Exposure angles
automatically
Roll& Pitch ≤
Heading ≤
GCP spread
automatically
Checking the spread
with reference to the
images footprints
AT accuracy
manually
Stereoscopic
measuring of GCP’s
Table 4: QC procedures
3.2 Chapter B
This chapter describes the processing steps and procedures to
generate a multi spectral Orthophoto with the accuracies set by
the DGI.
The Orthophoto generation should be based on the aerial
triangulation block and data from neighbouring blocks.
3.2.1 Geometric
To assure that the Orthophoto stands to the standards of the DGI
in terms of geometrics, the data provider is expected to use these
data sets:
a. Image parameters
b. 10 meter resolution DEM
c. Aerial triangulation report
d. Camera calibration report
e. Ground control points
The production procedure requires the ortho rectification of all
images captured and a mosaicking procedure that calculates the
most nadir part of each image.
The use of images and ground control points from neighbouring
blocks is needed for the geometric continuity of the product.
3.2.2 Radiometric
The generation of a national scale Orthophoto captured with
variant sensors and during a period of a few mounts can be very
challenging in terms of color balance uniformity, in order to
achieve optimized product the DGI provides basic guidelines:
a. During the aerial capture stage, every flight mission
needs to be focused in one geographic area.
b. For each area captured (~5,000 km2) all raw images
needs to be color adjusted during the aerial
triangulation stage (the use of tie points is highly
recommended).
c. During the Orthophoto production stage, images from
neighboring areas must be used in the color balance
stage, in case adjective ortho blocks area captured by
different sensors, the provider must also use images
from the other sensor to best preform the color
adjustment.
3.2.3 Quality Control
Due to the fact that the visual aspect of the Orthophoto draws
most of the attention from the end users, a large amount of
resources goes to the radiometric quality of the product but the
geometric accuracy is not less important and focus on 2 main
topics:
a. The horizontal accuracy measured in respect to known
measured points located on the ground; acceptable
horizontal accuracy in terms of RMSE was set to
maximum.
b. Relief displacement is measured in respect to known
buildings heights in several areas in the Orthophoto,
acceptable relief displacement describe in formula (1):
(1)
Where relative is the relative building height above the
ground.
The radiometric quality control procedures focus on the topics
which describe in table (5):
Subject
Testing method
Procedure
Tone histogram
automatically
Validating the tone
spread reflects the
real colours of the
captured area
Contrast
visually
Looking for details in
areas with high light
and dark shadows
Sharpness
visually
Being able to detect
features according to
the capture resolution
Band ratio
automatically
Checking NDVI,
NWDI
Radiometric
uniformity
manually
Checking uniformity
of neighbouring areas
Table 5: Chapter B Radiometric QC procedures
3.3 Chapter C
This document refers only to height elevation models produced
by photogrammetric methods. The production must be done semi
automatically and by using the aerial triangulation data.
3.3.1 Point Clouds
The point clouds generated automatically needs to be cleaned
manually of any spikes and noises, the product's minimum point
spacing should be 8 points per m2.
The point clouds needs to be classified automatically into bear
earth - points describing the ground and elements of the ground
such as terraces, quarries, roads etc. will be classified into ground
class and points describing manmade objects such as buildings,
bridges, culverts, walls etc. or vegetation will be classified into
non-ground class. Manual classification is needed following the
automatic procedure in order to achieve 95% validation. The
automatic classification of vegetation is expected to use the color
values of the point cloud (NIR values are preferred but not
obliged).
3.3.2 DSM & DTM
The DTM and DSM will be calculated based on the classified
point clouds- the DTM will be a regular surface describing the
points classified to ground at a special resolution of 50 cm and
the DSM will be a regular surface describing the points classified
to ground and non-ground at a special resolution of 50 cm.
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLIII-B2-2022
XXIV ISPRS Congress (2022 edition), 6–11 June 2022, Nice, France
This contribution has been peer-reviewed.
https://doi.org/10.5194/isprs-archives-XLIII-B2-2022-65-2022 | © Author(s) 2022. CC BY 4.0 License.
68
3.3.3 Quality Control
The quality control stage of the height elevation modules will be
done for both the point clouds data and the DSM & DTM raster’s.
Point clouds will be tested to ensure the quality of the DSM &
DTM and there for the objective of the procedure will be to
ensure the point density and the quality of the classification.
The raster’s will be tested to ensure the accuracy and reliability
of the data.
Most of the procedures are done automatically running a code
going over the files and flagging the mistakes but some will be
done manually. Table (6) describes the procedures and their
objectives:
Objective
Data set
Procedure
Point density
Point
clouds
≥ 8 points per m2
Non-ground features
classification
Point
clouds
See below formula (2)
Noise free DSM
DSM &
DTM
nDSM clean of spikes
which are not objects
of the DSM (see
below formula (3))
Water bodies
DSM &
DTM
Water bodies must be
flat and clean of
noises
No data values
DSM &
DTM
Only permitted at the
edges of the covered
area
Spatial accuracy
DSM &
DTM
Table 6: Chapter C DTM&DSM QC procedures
(2)
Where is the relative height of the object from the ground
surrounding it.
(3)
4. SUMMERY
Flowing the publication of the standard, in 2019 the SOI has
issued a tender for nationwide aerial acquisition and the
production of nationwide mapping products and since then has
covered the country 3 times. The tender stated the minimum
terms a service provider must qualify (certified camera system,
minimum experience etc.) and 3 contracts were selected.
The total area of Israel was divided into 8 capturing zones and
each contractor was given a zone to start with, winning the next
zone after the successful compliance of the production.
The aerial capturing resolution was set to 20cm to produce the
mapping products that meets the government and public needs.
Regarding the objectives of the standard and after 3 years running
the bid we can conclude that the standard objectives are
achievable.
The next step should be to expand the standard to higher
geospatial resolution for smaller project areas such as municipal
areas under massive construction development. A special
attention needs to be given to oblique imagery capturing and 3D
photo realistic models in order to support decision making in the
era of urban planning.
Figure 4: the 8 areas division of Israel and the 2021 ortho cover
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLIII-B2-2022
XXIV ISPRS Congress (2022 edition), 6–11 June 2022, Nice, France
This contribution has been peer-reviewed.
https://doi.org/10.5194/isprs-archives-XLIII-B2-2022-65-2022 | © Author(s) 2022. CC BY 4.0 License.
69
REFERENCES
ASPRS, Hussain M., Bethel J., (2004) Manual of
Photogrammetry, fifth Edition Chapter 15, Project and Mission
Planning
ASPRS (2014) ASPRS Positional Accuracy Standards for Digital
Geospatial Data Ed.1, Ver. 1.0. doi: 10.14358/PERS.81.3.A1-
A26
Felus Y., Keinan E., Regev R., (2013) Regulations in the field
of Geo-Information, International Archives of the
Photogrammetry, Remote Sensing and Spatial Information
Sciences, Volume XL-7/W2, ISPRS2013-SSG, Turkey
doi:10.5194/isprsarchives-XL-7-W2-87-2013
Felus Y. , Keinan E. , Benhamu M. ,Regev R., Zalmanzon G.
(2016), The International Archives of the Photogrammetry,
Remote Sensing and Spatial Information Sciences, Volume XLI-
B1, 2016 XXIII ISPRS Congress, Prague, Czech Republic
doi: 10.5194/isprsarchives-XLI-B1-179-2016
Kapnias D., Milenov P. and Kay S. (2008), Guidelines for Best
Practice and Quality Checking of Ortho Imagery at:
https://publications.jrc.ec.europa.eu/repository/bitstream/JRC48
904/10133.pdf
DOI 10.2788/36028
Land information New Zealand (2014), Guidelines on geo-
referencing and orthorectification of historic aerial imagery at:
https://www.linz.govt.nz/system/files_force/media/file-
attachments/Georeferencing%20and%20orthorectification%20g
uidelines%202014%20.pdf
Land information New Zealand (2013), Specifications relating
to the acquisition of orthophotography at:
https://www.linz.govt.nz/system/files_force/media/file-
attachments/SpecificationRelatingAcquisitionOrthophotography
.doc
Annex 1
Table 2: Accuracy level, GCP and AT Accuracy
Geospatial products levels
GSD
(cm)
Largest
scale
Contour
line
interval
(m)
GCP RMSE (m)
AT RMSE (m)
Horizontal
Vertical
East/North
Vertical
East/North
Vertical
3
3
2.5
1:250
0.25
0.030
0.025
0.05
0.04
4
4
5
1:500
0.50
0.065
0.050
0.10
0.08
5
5
7.5
1:1,000
1.00
0.125
0.100
0.20
0.16
6
6
10
1:1,250
1.25
0.150
0.125
0.25
0.2
7
7
12.5
1:2,500
2.50
0.315
0.250
0.50
0.4
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLIII-B2-2022
XXIV ISPRS Congress (2022 edition), 6–11 June 2022, Nice, France
This contribution has been peer-reviewed.
https://doi.org/10.5194/isprs-archives-XLIII-B2-2022-65-2022 | © Author(s) 2022. CC BY 4.0 License.
70
