Map Library Usage

The Geospatial Data Abstraction Library (GDAL) WMS driver supports several internal 'minidrivers' that allow access to different web mapping services. Each of these services may support a different set of options in the Service block. Documentation for these minidrivers can be found here on the GDAL website. Two of these minidrivers in particular can be used by users to download GIBS imagery programmatically. They are the Tile Map Specification (TMS) and the OnEarth Tiled WMS (TiledWMS) minidrivers. Examples for both of these minidrivers will be included below.

Requirements

GDAL version 1.9.1 or greater with cURL support enabled. To check if cURL is enabled for GDAL, type "gdalinfo --format WMS". If cURL is enabled you will see information about the WMS format, if not, you will get an error message and you will need to reconfigure GDAL to support cURL.

Sample Execution #1 - "TMS" Driver Configuration File Input

Create a local service description XML file and invoke gdal_translate. In this example, GIBS_Aqua_MODIS_true.xml is used to generate a true color JPEG image from Aqua MODIS of a smoke plume from western fires over the central United States. The contents of GIBS_Aqua_MODIS_true.xml would be:

<GDAL_WMS>
    <Service name="TMS">
        <ServerUrl>https://gibs.earthdata.nasa.gov/wmts/epsg4326/best/MODIS_Aqua_CorrectedReflectance_TrueColor/default/2013-08-21/250m/${z}/${y}/${x}.jpg</ServerUrl>
    </Service>
    <DataWindow>
        <UpperLeftX>-180.0</UpperLeftX>
        <UpperLeftY>90</UpperLeftY>
        <LowerRightX>396.0</LowerRightX>
        <LowerRightY>-198</LowerRightY>
        <TileLevel>8</TileLevel>
        <TileCountX>2</TileCountX>
        <TileCountY>1</TileCountY>
        <YOrigin>top</YOrigin>
    </DataWindow>
    <Projection>EPSG:4326</Projection>
    <BlockSizeX>512</BlockSizeX>
    <BlockSizeY>512</BlockSizeY>
    <BandsCount>3</BandsCount>
</GDAL_WMS>

gdal_translate -of GTiff -outsize 1200 1000 -projwin -105 42 -93 32 GIBS_Aqua_MODIS_true.xml GreatPlainsSmoke1.tif
gdal_translate -of JPEG GreatPlainsSmoke1.tif GreatPlainsSmoke1.jpg

In very limited testing, our experience has been that better image quality is obtained by using the GeoTIFF output format from the GDAL WMS, then converting this to other formats, if desired, using a second gdal_translate command, or other programs such as ImageMagick convert.

Sample Execution #2 - "TMS" Driver Command Line Input

Invoke gdal_translate with the content of the local service description XML file embedded into the command.  This approach is useful for automated scripting to download various layers, dates, etc.  To generate the same image as above:

gdal_translate -of GTiff -outsize 1200 1000 -projwin -105 42 -93 32 '<GDAL_WMS><Service name="TMS"><ServerUrl>https://gibs.earthdata.nasa.gov/wmts/epsg4326/best/MODIS_Aqua_CorrectedReflectance_TrueColor/default/2013-08-21/250m/${z}/${y}/${x}.jpg</ServerUrl></Service><DataWindow><UpperLeftX>-180.0</UpperLeftX><UpperLeftY>90</UpperLeftY><LowerRightX>396.0</LowerRightX><LowerRightY>-198</LowerRightY><TileLevel>8</TileLevel><TileCountX>2</TileCountX><TileCountY>1</TileCountY><YOrigin>top</YOrigin></DataWindow><Projection>EPSG:4326</Projection><BlockSizeX>512</BlockSizeX><BlockSizeY>512</BlockSizeY><BandsCount>3</BandsCount></GDAL_WMS>' GreatPlainsSmoke2.tif
gdal_translate -of JPEG GreatPlainsSmoke2.tif GreatPlainsSmoke2.jpg

For both options, the information needed to create the local service description XML can be found in the large table on the GIBS Available Imagery Products page.

Items that may need to be changed include:

1) <ServerUrl>https://gibs.earthdata.nasa.gov/wmts/epsgcode/best/layer_name/default/date/resolution/${z}/${y}/${x}.format</ServerUrl>

layer_name - use "Layer Name on Server" from Products page. Note that only one layer can be retrieved per gdal_translate call.

date - use the desired date in YYYY-MM-DD format

epsgcode - use "epsg" followed by the appropriate EPSG code from Footnote 4 on the GIBS Available Imagery Products page

resolution - use the "Resolution" in the format ####m from the "Imagery Resolution" column on the GIBS Available Imagery Products page, or GoogleMapsCompatible_Level# resolution from table below

format - use jpg or png extension based on the "Format"

2) Bounding box - use -180.0, 90, 396.0, -198 for Geographic projection and -4194304, 4194304, 4194304, -4194304 for the Polar projections. This is the bounding box of the topmost tile, which matches the bounding box of the actual imagery for Polar but not for Geographic.

3) <TileLevel> - select from the table below based on "Resolution" and "Projection".  Note that the TileLevel in the table below is the maximum for that resolution.  You can specify a lower value of TileLevel to force GDAL to use coarser resolution input tiles.  This can be used to speed up projection, for example during development and testing.

4) <TileCountX><TileCountY> - use 2, 1 for Geographic projection and 2, 2 for Polar projections

5) <Projection>  - use the appropriate EPSG code from Footnote 4 on the GIBS Available Imagery Products page.

6) <Bands> - use 3 for .jpg (except use 1 for ASTER_GDEM_Greyscale_Shaded_Relief) and 4 for .png

Note that the values for <YOrigin>, <BlockSizeX>, and <BlockSizeY> are constant for all GIBS layers.

More information on GDAL_WMS can be found here (note the "TMS" section). 

Sample Execution #3 - "TiledWMS" Driver Configuration File Input

The TiledWMS GDAL minidriver relies on a simplified set of XML configuration from the user, pulling all other information from the TWMS WMS_Tile_Service document at runtime. The following example requests the same image as was requested in Sample Execution #1, but you will notice how much simpler the XML configuration is. The primary difference is that requests through TWMS utilize a TiledGroupName value instead of the WMTS Identifier utilized by WMTS requests. In almost all cases the TiledGroupName can be generated by replacing all underscores in a WMTS layer's Identifier with spaces and appending " tileset". For example, a WMTS Layer Identifier of SMAP_L1_Passive_Faraday_Rotation_Aft" becomes the TWMS TiledGroupName "SMAP L1 Passive Faraday Rotation Aft tileset". Unfortunately there are a few exceptions, which include the sample layer used below.

<GDAL_WMS>
  <Service name="TiledWMS">
    <ServerUrl>https://gibs.earthdata.nasa.gov/twms/epsg4326/best/twms.cgi?</ServerUrl>
    <TiledGroupName>MODIS AQUA tileset</TiledGroupName>
    <Change key="${time}">2013-08-21</Change>
  </Service>
</GDAL_WMS>

gdal_translate -of GTiff -outsize 1200 1000 -projwin -105 42 -93 32 GIBS_Aqua_MODIS_true.xml GreatPlainsSmoke1.tif
gdal_translate -of JPEG GreatPlainsSmoke1.tif GreatPlainsSmoke1.jpg

gdal_translate -of GTiff -outsize 1200 1000 -projwin -105 42 -93 32 '<GDAL_WMS><Service name="TiledWMS"><ServerUrl>https://gibs.earthdata.nasa.gov/twms/epsg4326/best/twms.cgi?</ServerUrl><TiledGroupName>MODIS AQUA tileset</TiledGroupName><Change key="${time}">2013-08-21</Change></Service></GDAL_WMS>' GreatPlainsSmoke2.tif
gdal_translate -of JPEG GreatPlainsSmoke2.tif GreatPlainsSmoke2.jpg

Configuration File Input w/ Transparent PNG 

In this example, GIBS_OMI_AI.xml is used to generate a transparent PNG image from the OMI Aerosol Index over the same region as the first two examples.  The "Layer Name on Server" and EPSG/resolution in <ServerURL>,  the <TileLevel>, and the <BandsCount> have changed from the first examples.  The contents of GIBS_OMI_AI.xml would be:

<GDAL_WMS>
    <Service name="TMS">
        <ServerUrl>https://gibs.earthdata.nasa.gov/wmts/epsg4326/best/OMI_Aerosol_Index/default/2013-08-21/2km/${z}/${y}/${x}.png</ServerUrl>
    </Service>
    <DataWindow>
        <UpperLeftX>-180.0</UpperLeftX>
        <UpperLeftY>90</UpperLeftY>
        <LowerRightX>396.0</LowerRightX>
        <LowerRightY>-198</LowerRightY>
        <TileLevel>5</TileLevel>
        <TileCountX>2</TileCountX>
        <TileCountY>1</TileCountY>
        <YOrigin>top</YOrigin>
    </DataWindow>
    <Projection>EPSG:4326</Projection>
    <BlockSizeX>512</BlockSizeX>
    <BlockSizeY>512</BlockSizeY>
    <BandsCount>4</BandsCount>
</GDAL_WMS>

gdal_translate -of GTiff -outsize 1200 1000 -projwin -105 42 -93 32 GIBS_OMI_AI.xml GreatPlainsSmokeAI.tif
gdal_translate -of PNG GreatPlainsSmokeAI.tif GreatPlainsSmokeAI.png

Polar Imagery

In this example, GIBS_Terra_MODIS_Arctic.xml is used to generate a true color JPEG image from Terra MODIS of a phytoplankton bloom in the Barents Sea. The "Layer Name on Server" and EPSG/resolution in <Serverurl>,  the <DataWindow> elements, and the <Projection> have changed from the first examples.  The contents of GIBS_Terra_MODIS_Arctic.xml would be:

<GDAL_WMS>
    <Service name="TMS">
        <ServerUrl>https://gibs.earthdata.nasa.gov/wmts/epsg3413/best/MODIS_Terra_CorrectedReflectance_TrueColor/default/2013-08-01/250m/${z}/${y}/${x}.jpg</ServerUrl>
    </Service>
    <DataWindow>
        <UpperLeftX>-4194304</UpperLeftX>
        <UpperLeftY>4194304</UpperLeftY>
        <LowerRightX>4194304</LowerRightX>
        <LowerRightY>-4194304</LowerRightY>
        <TileLevel>5</TileLevel>
        <TileCountX>2</TileCountX>
        <TileCountY>2</TileCountY>
        <YOrigin>top</YOrigin>
    </DataWindow>
    <Projection>EPSG:3413</Projection>
    <BlockSizeX>512</BlockSizeX>
    <BlockSizeY>512</BlockSizeY>
    <BandsCount>3</BandsCount>
</GDAL_WMS>

GeoTIFF files created by GDAL using the default tags for the GIBS polar projections do not work correctly in some GIS programs.  So we recommend specifying the output projection in PROJ4 format:

gdal_translate -of GTiff -outsize 980 940 -a_srs "+proj=stere +lat_0=90 +lat_ts=70 +lon_0=-45 +k=1 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs" -projwin 1520000 240000 2500000 -700000 GIBS_Terra_MODIS_Arctic.xml BarentsSea.tif
gdal_translate -of JPEG BarentsSea.tif BarentsSea.jpg

The projection string for the GIBS Antarctic projection is "+proj=stere +lat_0=-90 +lat_ts=-71 +lon_0=0 +k=1 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs".  Here are the links for the Arctic or Antarctic PROJ4 definitions.  Some other workarounds are:

1)  Use a ".aux.xml" file with the ".tif" file.  Download the sample Arctic or Antarctic XML file and rename it to match the GeoTIFF file.

gdal_translate -of GTiff -outsize 980 940 -projwin 1520000 240000 2500000 -700000 GIBS_Terra_MODIS_Arctic.xml BarentsSea.tif
"copy" GIBS_Arctic_3413.tif.aux.xml "to"  BarentsSea.tif.aux.xml
gdal_translate -of JPEG BarentsSea.tif BarentsSea.jpg

2) Use JPEG format instead. This will create a .jpg.aux.xml file in addition to the .jpg file.

gdal_translate -of JPEG -outsize 980 940 -projwin 1520000 240000 2500000 -700000 GIBS_Terra_MODIS_Arctic.xml BarentsSea.jpg

Polar Layer w/ Reprojection

In this example,  GIBS_Aqua_MODIS_Arctic.xml is used to generate a true color JPEG image from Aqua MODIS of the Beaufort Sea reprojected to have 145W down. The "Layer Name on Server" and EPSG/resolution in <Serverurl>,  the <DataWindow> elements, and the <Projection> have changed from the first examples.  The contents of GIBS_Aqua_MODIS_Arctic.xml would be:

<GDAL_WMS>
    <Service name="TMS">
        <ServerUrl>https://gibs.earthdata.nasa.gov/wmts/epsg3413/best/MODIS_Aqua_CorrectedReflectance_TrueColor/default/2013-06-20/250m/${z}/${y}/${x}.jpg</ServerUrl>
    </Service>
    <DataWindow>
        <UpperLeftX>-4194304</UpperLeftX>
        <UpperLeftY>4194304</UpperLeftY>
        <LowerRightX>4194304</LowerRightX>
        <LowerRightY>-4194304</LowerRightY>
        <TileLevel>5</TileLevel>
        <TileCountX>2</TileCountX>
        <TileCountY>2</TileCountY>
        <YOrigin>top</YOrigin>
    </DataWindow>
    <Projection>EPSG:3413</Projection>
    <BlockSizeX>512</BlockSizeX>
    <BlockSizeY>512</BlockSizeY>
    <BandsCount>3</BandsCount>
</GDAL_WMS>

gdalwarp -t_srs '+proj=stere +lat_0=90 +lat_ts=70 +lon_0=-145 +k=1 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs' -te -1600000 -2500000 1200000 -400000 -tr 1000 1000 GIBS_Aqua_MODIS_Arctic.xml Beaufort_neg145down_1km.tif
gdal_translate -of JPEG Beaufort_neg145down_1km.tif Beaufort_neg145down_1km.jpg

Reprojecting GIBS Geographic layer into Polar Stereographic

Only a subset of layers are available from GIBS in the polar projections. This is an example of how to project a geographic layer into a polar projection.  The contents of GIBS_Terra_Cloud_Fraction.xml would be:

<GDAL_WMS>
    <Service name="TMS">
        <ServerUrl>https://gibs.earthdata.nasa.gov/wmts/epsg4326/best/MODIS_Terra_Cloud_Fraction_Day/default/2017-05-16/2km/${z}/${y}/${x}.png</ServerUrl>
    </Service>
    <DataWindow>
        <UpperLeftX>-180.0</UpperLeftX>
        <UpperLeftY>90</UpperLeftY>
        <LowerRightX>396.0</LowerRightX>
        <LowerRightY>-198</LowerRightY>
        <TileLevel>5</TileLevel>
        <TileCountX>2</TileCountX>
        <TileCountY>1</TileCountY>
        <YOrigin>top</YOrigin>
    </DataWindow>
    <Projection>EPSG:4326</Projection>
    <BlockSizeX>512</BlockSizeX>
    <BlockSizeY>512</BlockSizeY>
    <BandsCount>4</BandsCount>
    <ZeroBlockHttpCodes>204,404,400</ZeroBlockHttpCodes>
</GDAL_WMS>

gdalwarp -wo SOURCE_EXTRA=100 -wo SAMPLE_GRID=YES -of GTiff -t_srs "+proj=stere +lat_0=90 +lat_ts=70 +lon_0=-45 +k=1 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs" -ts 4096 4096 -te -4194304 -4194304 4194304 4194304 GIBS_Terra_Cloud_Fraction.xml Terra_Cloud_Fraction_Arctic.tif

The "-wo SOURCE_EXTRA=100 -wo SAMPLE_GRID=YES" arguments are needed to ensure that the output region is completely filled.  The "-wo SOURCE_EXTRA=100" caused GDAL to request tiles outside of input bounding region.  Normally GDAL would halt when it receives these errors so the <ZeroBlockHttpCodes> includes the 400 error to allow GDAL to continue.  Note that this command may take a long time to complete, especially at higher input and output resolutions.