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Earth Explorer Example

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Leslie Keely edited this page May 17, 2017 · 10 revisions

Earth Explorer is a USGS website that allows users to search for and download imagery and other cartographic data products.

Data Credit: USGS

Mount Everest

1.) Go to Earth Explorer and type in "Mount Everest" in the Address/Place field. Press Show and then click on the Mount Everest link.

2.) Zoom and pan until the peak fills your window. Click Use Map under the Coordinates tab.

3.) Go to the Data Sets tab and select NASA LPDAAC Collections > NASA SRTM (SRTM 3) Collections > NASA SRTM3 SRTMGL1 and Landsat Archive > L8 OLI/TIRS. Next select the Results tab.

4.) View image footprints and download co-located or overlapping SRTM and LandSAT files.

5.) Convert .hgt files to GeoTIFF with gdal_translate.

6.) If you have more than one DEM file, stitch them together:

gdalwarp N27E086.tif N27E087.tif N28E086.tif N28E087.tif dem.tif

7.) Untar the LandSAT file and create a color orthoimage (use gdalinfo to find minimum and maximum).

gdal_translate -scale 0 56159 0 255 -ot Byte LC81400412016084LGN00_B4.TIF red.tif
gdal_translate -scale 0 54288 0 255 -ot Byte LC81400412016084LGN00_B3.TIF green.tif
gdal_translate -scale 0 55258 0 255 -ot Byte LC81400412016084LGN00_B2.TIF blue.tif
gdal_merge.py -separate red.tif green.tif blue.tif -o colorRGB.tif

8.) Sharpen with panchromatic band using hsv_merge.py.

gdal_translate -scale 0 56913 0 255 -ot Byte LC81400412016084LGN00_B8.TIF gray.tif
gdalwarp -ts 15301 15621 -r bilinear colorRGB.tif colorRGBx2.tif
./hsv_merge.py colorRGBx2.tif gray.tif color.tif

9.) Run gdalinfo on the color.tif and copy and paste the projection into ortho.prj. The file should look like the following:

PROJCS["WGS 84 / UTM zone 45N",
    GEOGCS["WGS 84",
        DATUM["WGS_1984",
            SPHEROID["WGS 84",6378137,298.257223563,
                AUTHORITY["EPSG","7030"]],
            AUTHORITY["EPSG","6326"]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433],
        AUTHORITY["EPSG","4326"]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",87],
    PARAMETER["scale_factor",0.9996],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AUTHORITY["EPSG","32645"]]

10.) Project the DEM.

gdalwarp -t_srs ortho.prj -r bilinear -tr 60 60 dem.tif proj_dem.tif

11.) Crop the orthoimage and the DEM to the same physical area:

gdal_translate -projwin 441352.5 3121387.5 541912.5 2998507.5 color.tif orthoimage.tif
gdal_translate -projwin 441352.5 3121387.5 541912.5 2998507.5 proj_dem.tif proj_dem_cropped.tif

12.) Create a landscape directory called MountEverest.

13.) Create the layers:

layerfactory -type=elevation -file=proj_dem_cropped.tif -landscape=MountEverest -tilesize=128
layerfactory -type=colorimage -file=orthoimage.tif -landscape=MountEverest -tilesize=512

14.) View MountEverest in DERT.

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