Christopher F. Brown’s research while affiliated with Google Inc. and other places

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Publications (3)


Not-so-random forests: Comparing voting and decision tree ensembles for characterizing partial harvest events
  • Article

December 2023

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29 Reads

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5 Citations

International Journal of Applied Earth Observation and Geoinformation

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Christopher F. Brown

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[...]

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Jonathan R. Thompson


Global distribution of annotated Sentinel-2 image tiles used for model training and periodic testing (neither including 409 validation tiles). (a) 4,000 tiles interpreted by a group of 25 experts (b) 20,000 tiles interpreted by a group of 45 non-experts. Hexagons represent approximately 58,500 km² areas and shading corresponds to the count of annotated tile centroids per hexagon.
Sentinel-2 tile and example reference annotation provided as part of interpreter training. This example was used to illustrate the Flooded vegetation class, which is distinguished by small “mottled” areas of water mixed with vegetation near a riverbed. Also note that some areas of the tile are left unlabeled.
Training inputs workflow. Annotations created using Sentinel-2 Level 2 A Surface Reflectance imagery are paired with masked and normalized Sentinel-2 Level 1 C Top of Atmosphere imagery, and inputs are augmented to create training inputs used for modeling. Cloud and shadow masking involves a three-step process that combines the Sentinel-2 Cloud Probability (S2C) product with the Cloud Displacement Index (CDI), which is used to correct over-masking of bright non-cloud targets” and directional distance transform (DDT), which is used to remove the expected path of shadows based on sun-sensor geometry.
Training protocol used to recover the labeling model. The bottom row shows the progression from a normalized Sentinel-2 L1C image, to class probabilities, to synthesized Sentinel-2. The dashed red and blue arrows show how the labeling model is optimized with respect to both the class probability and synthesis pathway, and the synthesis model is optimized only with respect to the synthesized imagery. The example image is retrieved from Earth Engine using ee.Image(‘GOOGLE/DYNAMICWORLD/V1/20190517T083601_20190517T083604_T37UET’).
Near-Real-Time (NRT) prediction workflow. Input imagery is normalized following the same protocol used in training and the trained model is applied to generate land cover predictions. Predicted results are masked to remove cloud and cloud shadow artifacts using Sentinel-2 cloud probabilities (S2C), the Cloud Displacement Index (CDI) and a directional distance transform (DDT), then added to the Dynamic World image collection.

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Dynamic World, Near real-time global 10 m land use land cover mapping
  • Article
  • Full-text available

June 2022

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2,276 Reads

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584 Citations

Scientific Data

Unlike satellite images, which are typically acquired and processed in near-real-time, global land cover products have historically been produced on an annual basis, often with substantial lag times between image processing and dataset release. We developed a new automated approach for globally consistent, high resolution, near real-time (NRT) land use land cover (LULC) classification leveraging deep learning on 10 m Sentinel-2 imagery. We utilize a highly scalable cloud-based system to apply this approach and provide an open, continuous feed of LULC predictions in parallel with Sentinel-2 acquisitions. This first-of-its-kind NRT product, which we collectively refer to as Dynamic World, accommodates a variety of user needs ranging from extremely up-to-date LULC data to custom global composites representing user-specified date ranges. Furthermore, the continuous nature of the product’s outputs enables refinement, extension, and even redefinition of the LULC classification. In combination, these unique attributes enable unprecedented flexibility for a diverse community of users across a variety of disciplines. Measurement(s)land use • land coverTechnology Type(s)deep learning Measurement(s) land use • land cover Technology Type(s) deep learning

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Citations (3)


... Temporal features characterizing the duration and severity of past disturbance events and forest recovery are commonly used to improve the accuracy of forest structure and land use/land cover models [7,19,74,75]. In total, 152 temporal features were computed using the LandTrendr and CCDC algorithms. ...

Reference:

A Large-Scale Inter-Comparison and Evaluation of Spatial Feature Engineering Strategies for Forest Aboveground Biomass Estimation Using Landsat Satellite Imagery
Not-so-random forests: Comparing voting and decision tree ensembles for characterizing partial harvest events
  • Citing Article
  • December 2023

International Journal of Applied Earth Observation and Geoinformation

... To verify the quality of the processed satellite data, each image was visually inspected and the spectral curves were evaluated at random points. A CloudScore+ mask product was applied with a scale of 0 to 1, denoting occluded and unoccluded observations, respectively (Pasquarella et al., 2023). Histogram-based thresholding was employed, utilising a cutoff of 0.75 to exclude pixels affected by clouds, cloud shadows, and other image distortions, such as excessive pixel saturation. ...

Comprehensive quality assessment of optical satellite imagery using weakly supervised video learning
  • Citing Conference Paper
  • June 2023

... To better understand the spatial characteristics of vertical ground motion, we supplemented the EGMS data with a land cover map (LCM). LCMs are valuable for tracking human activity, natural processes, and the impacts of climate change on land cover (Brown et al., 2022). They enable the detection of changes in urban areas, infrastructure, forests, and water bodies, critical information for policymaking, land development, and resource management (Wang et al., 2023). ...

Dynamic World, Near real-time global 10 m land use land cover mapping

Scientific Data