Knowledge Base

How to import and geolocate SMAP Level-3 and Level-4 data in ENVI

The following are instructions on how to import and geolocate SMAP Level-3 Radiometer Soil Moisture HDF5 data in ENVI.

Testing notes

Software: ENVI

Software version: 5.3

Platform: Windows 7

Data set: SMAP L3 Radiometer Global Daily 36 km EASE-Grid Soil Moisture (SPL3SMP)

Data set version: 2

Date tested: 12/17/15

Note: These instructions apply to the SPL3SMP data set, but only need slight modifications to apply to the other SMAP Level-3 soil moisture data sets (SPL3SMA, SPL3SMAP) and the SMAP Level-4 data sets (SPL4SMAU, SPL4SMGP, SPL4CMDL, SPL4SMLM).

1. Obtain data.

  • Download the SMAP Level-3 Radiometer Soil Moisture file of interest to you (e.g., SMAP_L3_SM_P_20151205_R12170_001.h5).
  • Download the appropriate latitude (e.g., EASE2_M36km.lats.964x406x1.double) and longitude (e.g., EASE2_M36km.lons.964x406x1.double) files and associated header files (e.g., EASE2_M36km.lats.964x406x1.hdr and EASE2_M36km.lons.964x406x1.hdr). Make sure all four of these files are in the same directory.

2. Open SMAP data in ENVI.

  • Start ENVI and select File > Open…
    Select the SMAP data file (e.g., SMAP_L3_SM_P_20151205_R12170_001.h5).
  • In the Dataset Browser, select the dataset(s) that you would like to display (e.g., Soil_Moisture_Retrieval_Data/soil_moisture). Add these to the Raster Builder using the arrow icon. Note that you may want to add a new raster for each SMAP dataset that you select.
  • Select Open Rasters.

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3. Build a Geographic Lookup Table (or, GLT).

  • In the Toolbox, select Geometric Correction > Build GLT.
  • In the Input X Geometry Band dialog box, select Open > New File and select the longitude file (e.g., EASE2_M36km.lons.964x406x1.double).
  • Click OK.

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  • In the Input Y Geometry Band dialog box, select Open > New File and select the latitude file (e.g., EASE2_M36km.lats.964x406x1.double).
  • Click OK.
  • In the Geometry Projection Information dialog box, select the following parameters:

                Input Projection of Geometry Bands: Geographic Lat/Lon

Datum: WGS-84

Units: Degrees

Output Projection for Georeferencing: Geographic Lat/Lon

                Datum: WGS-84

                Units: Degrees

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  • Click OK.
  • In the Build Geometry Lookup File Parameters dialog box:

Change the Output Rotation to 0.

Select Choose (for Enter Output GLT Filename) and provide a location and name for the output GLT file.

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  • Click OK.

4. Georeference the SMAP data from the GLT.

  • In the Toolbox, select Geometric Correction > Georeference from GLT.
  • In the Input Geometry Lookup File dialog box, select the GLT file you just built.

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  • Click OK.
  • In the Input Data File dialog box, select the SMAP data file.

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  • Click OK.
  • In the Georeference from GLT Parameters dialog box, select Choose (for Enter Output Filename) and provide a location and name for the output data file.

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  • Click OK.

And, now you have a geolocated raster!

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