SNAP GPT -PmapProjection parameter

Hi,

I’ve been having some issues with using GPT to perform a terrain correction of a Sentinel-1 Product and output to a GeoTiff using the AUTO:42001 map projection.

If I run the command below, it does generate an output but the spatial reference is EPSG:4326. Is this a bug or do i need to edit my command?

gpt Terrain-Correction -Ssource=“C:\testing\S1A_IW_GRDH_1SDV_20180806T175121_20180806T175146_023129_028321_19BB.zip” -PnodataValueAtSea=False -PimgResamplingMethod=BILINEAR_INTERPOLATION -PmapProjection=“AUTO:42001” -PsourceBands=Amplitude_VV -t "C:\testing\terrain_correction_utm.tif

My gdalinfo output shows the spatial reference as WGS 84:

Driver: GTiff/GeoTIFF
Files: .\terrain_correction_utm.tif
Size is 29158, 21577
Coordinate System is:
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”]]
Metadata:
AREA_OR_POINT=Area
Image Structure Metadata:
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 0.0, 0.0)
Lower Left ( 0.0,21577.0)
Upper Right (29158.0, 0.0)
Lower Right (29158.0,21577.0)
Center (14579.0,10788.5)
Band 1 Block=29158x1 Type=Float32, ColorInterp=Gray

Im using Windows 10 and my SNAP environment is as follows:

SNAP Desktop implementation version: 6.0.0
SNAP Engine implementation version: 6.0.0
JRE: Java™ SE Runtime Environment 1.8.0_102-b14
JVM: Java HotSpot™ 64-Bit Server VM by Oracle Corporation
Memory: 10013 MiB

Any help is much appreciated, thanks.

EDIT 1

I’ve just run this again but saved my output to DIM format and it does honor the AUTO:42001 map projection. Is this the desired functionality i.e. use DIM format for output then use Convert-DataType to produce a GeoTiff?

EDIT 2

I’ve just run the workflow using Terrain-Correction (AUTO:42001, output to DIM) and then Convert-DataType (DIM to GeoTiff).

Terrain Correction
gpt Terrain-Correction -Ssource=“C:\testing\S1A_IW_GRDH_1SDV_20180806T175121_20180806T175146_023129_028321_19BB.zip” -PnodataValueAtSea=False -PimgResamplingMethod=BILINEAR_INTERPOLATION -PmapProjection=“AUTO:42001” -PsourceBands=Amplitude_VV -t "C:\testing\terrain_correction_utm.dim"

Convert Data Type
gpt Convert-DataType -Ssource="C:\testing\terrain_correction_utm.dim" -PsourceBands=Amplitude_VV - PtargetDataType=float32 -PtargetNoDataValue=0 -PtargetScalingStr=Truncate -t "C:\testing\terrain_utm_gptconvert.tif"

Now I have the situation where my terrain_correction_utm.dim file is using WGS 84 / Auto UTM but after running Convert-DataType my output GeoTiff, terrain_utm_gptconvert.tif, is output using WGS84 GCS. Interestingly the coordinates are not in degrees. The output from gdalinfo is shown below:

Driver: GTiff/GeoTIFF
Files: .\terrain_utm_gptconvert.tif
Size is 29158, 21577
Coordinate System is:
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”]]
Metadata:
AREA_OR_POINT=Area
Image Structure Metadata:
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 0.0, 0.0)
Lower Left ( 0.0,21577.0)
Upper Right (29158.0, 0.0)
Lower Right (29158.0,21577.0)
Center (14579.0,10788.5)

If I use gdal_translate to perform the conversion from the terrain_correction_utm.data\Amplitude_VV.img file to GeoTiff i get the desired result:

gdal_translate -of GTiff "C:\testing\terrain_correction_utm.data\Amplitude_VV.img" "C:\testing\terrain_utm_gdalconvert.tif"

Driver: GTiff/GeoTIFF
Files: .\terrain_utm_gdalconvert.tif
Size is 29158, 21577
Coordinate System is:
PROJCS[“WGS 84 / UTM zone 30N”,
GEOGCS[“WGS 84”,
DATUM[“WGS_1984”,
SPHEROID[“WGS 84”,6378137,298.257223563,
AUTHORITY[“EPSG”,“7030”]],
AUTHORITY[“EPSG”,“6326”]],
PRIMEM[“Greenwich”,0,
AUTHORITY[“EPSG”,“8901”]],
UNIT[“degree”,0.0174532925199433,
AUTHORITY[“EPSG”,“9122”]],
AUTHORITY[“EPSG”,“4326”]],
PROJECTION[“Transverse_Mercator”],
PARAMETER[“latitude_of_origin”,0],
PARAMETER[“central_meridian”,-3],
PARAMETER[“scale_factor”,0.9996],
PARAMETER[“false_easting”,500000],
PARAMETER[“false_northing”,0],
UNIT[“metre”,1,
AUTHORITY[“EPSG”,“9001”]],
AXIS[“Easting”,EAST],
AXIS[“Northing”,NORTH],
AUTHORITY[“EPSG”,“32630”]]
Origin = (387138.158923594750000,6562402.211472293400000)
Pixel Size = (10.000000000000000,-10.000000000000000)
Metadata:
AREA_OR_POINT=Area
Band_1=Amplitude_VV
Image Structure Metadata:
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 387138.159, 6562402.211) ( 4d58’30.99"W, 59d11’ 8.55"N)
Lower Left ( 387138.159, 6346632.211) ( 4d52’13.84"W, 57d14’55.71"N)
Upper Right ( 678718.159, 6562402.211) ( 0d 7’34.51"E, 59d 9’47.18"N)
Lower Right ( 678718.159, 6346632.211) ( 0d 2’21.75"W, 57d13’40.22"N)
Center ( 532928.159, 6454517.211) ( 2d26’21.53"W, 58d13’50.04"N)

I just tried your workflow. But with different data S3 OLCI and not with Terrain-Correction but just with Reprojection, but I used AUTO:42001.

That’s my gpt call:

gpt Reproject -Pcrs=AUTO:42001 -t G:\EOData\temp\utm-auto-test.tif G:\EOData\temp\subset_0_of_S3A_OL_1_EFR____20190214T070944_20190214T071244_20190215T112348_0179_041_220_2160_LN1_O_NT_002.dim

and that’s the output of gdalinfo:
utm-auto-test-gdal-info.txt (1.7 KB)

So, in general it works. The GeoTiff can store the information.
Maybe there is something special with the S1 data or the terrain correction.

@lveci can you check what’s going on?

1 Like

Thanks for your reply.

I tried using the Reproject function on my terrain_correction_utm.dim file but i got the same result i.e. result GeoTiff is in WG84.

gpt Reproject -Pcrs=AUTO:42001 -Ssource="C:\testing\terrain_correction _utm.dim" -PnoDataValue=0 -t "C:\testing\reproject_utm_near.tif"