Overview
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Terrain shadow masks (TSMs) were generated using a winter season scene over 4 different path/row locations in Australia.

The TSM algorithm is run on a terrain model using the shadow angle information provided with the Landsat scene.  The algorithm checks each terrain model pixel to determine if any other terrain blocks direct solar illumination of that pixel based on a geometric ray from that pixel to the Sun.  The length of the ray evaluated toward the Sun depends upon a horizontal distance computed from the highest elevation in the terrain model, the terrain elevation and solar elevation angle at the terrain pixel being evaluated, and the pixel dimensions of the terrain model.

In addition to the TSM, the algorithm generates a TSM Sensitivity Layer (TSL) that provides a numerical measure of how close each terrain pixel came to being categorized oppositely.  If a pixel is in shadow according to the TSM, the TSL value indicates the largest relative height of blocking terrain above the ray to the Sun.  If the pixel is not in shadow, the TSL value indicates the smallest relative height to other terrain below the ray to the Sun.  

For the Australian datasets, TSMs were generated using both the nominal Landsat Collection 2 terrain model and Copernicus GLO-30 terrain data obtained from ESA.  Additional diagnostic and support data layers are provided to assist with evaluation of the TSM algorithm.  Test site information and the coincident data layers are described below.


Datasets
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Blue Mountains
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Path/Row: 90/84
Collection Date: 2017-05-31
Satellite: Landsat 8
Scene ID: LC80900842017151LGN00
Processing Level: L1TP

Brisbane
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Path/Row: 89/79
Collection Date: 2015-06-04
Satellite: Landsat 8
Scene ID: LC80890792015155LGN01
Processing Level: L1TP

Snowy Mountains
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Path/Row: 91/85
Collection Date: 2020-07-17
Satellite: Landsat 8
Scene ID: LC80910852020199LGN00
Processing Level: L1TP

Tasmania
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Path/Row: 91/89
Collection Date: 2021-06-18
Satellite: Landsat 8
Scene ID: LC80910892021169LGN00
Processing Level: L1TP


Fundamental Data Layers
-----------------------

1) Terrain Shadow Mask (TSM): "shadow_mask_<algorithm>_<dem_type>_<dem_filename>_<EGM>_<rows_cols_processed>.tif"

Shadow pixels are set to 255.  All other pixels are set to 0.

<algorithm> is always "fully_rigorous" and refers to the most detailed geometric algorithm evaluated for the TSM effort.

<dem_type> is either "C2_DEM" (for the Landsat Collection 2 DEM) or "Copernicus_DEM" for this processing.  The algorithm does allow other map-projected DEMs to be used as input.

<dem_filename> is always "elev_pass_2" for this processing, which is generated by internal pre-processing of the input DEM.  

<EGM> is always set to "NoEGM" as the internal "elev_pass_2" DEM is already pre-processed into WGS-84 ellipsoid heights.

<rows_cols_processed> indicates the range of DEM rows and columns processed, e.g., "0_7951_0_7911" is from rows 0-7951 and from columns 0-7911, and is the entire DEM model for each of these examples.

2) TSM Sensitivity Layer (TSL): "tsm_sensitivity_layer_<dem_type>_<dem_filename>_<EGM>_<rows_cols_processed>.tif"


Diagnostic Data Layers
----------------------

1) Blocking Terrain Row (relative to TSM row toward Sun): "blocking_row_<algorithm>_<dem_type>_<dem_filename>_<EGM>_<rows_cols_processed>.tif"

2) Blocking Terrain Column (relative to TSM column toward Sun): "blocking_col_<algorithm>_<dem_type>_<dem_filename>_<EGM>_<rows_cols_processed>.tif"

3) Maximum Terrain Row Evaluated (relative to TSM row toward Sun): "max_row_<algorithm>_<dem_type>_<dem_filename>_<EGM>_<rows_cols_processed>.tif"

4) Maximum Terrain Column Evaluated (relative to TSM column toward Sun): "max_col_<algorithm>_<dem_type>_<dem_filename>_<EGM>_<rows_cols_processed>.tif"


Other Data Layers Provided
--------------------------

1) Collection 2 DEM (saved off by algorithm, in WGS-84 ellipsoid heights): "C2_DEM_<dem_filename>_<EGM>.tif"

2) Copernicus GLO-30 DEM (saved off by algorithm, in WGS-84 ellipsoid heights): "Copernicus_DEM_<dem_filename>_<EGM>.tif"

3) Collection 2 DEM Terrain-Shaded Relief (TSR) (created using QGIS): "C2_DEM_<dem_filename>_<EGM>_TSR.tif"

4) Copernicus DEM TSR (created using QGIS): "Copernicus_DEM_<dem_filename>_<EGM>_TSR.tif"

5) RGB Bands generated by both Collection 2 DEM and Copernicus DEM processing:

"<Scene ID>_B2.tif"
"<Scene ID>_B3.tif"
"<Scene ID>_B4.tif"

6) Metadata file generated by both Collection 2 DEM and Copernicus DEM processing: "<Scene ID>_MTL.txt"