I have finally figured out that l3mapgen has a small problem (or I'm missing something). When I generate a TIFF image with l3mapgen with:
I'm not clear on what values should exist to indicate not actual data values, but it would be convenient to be able to specify something like nodata=-32768 to override the default output. This would make it much easier to work with the gdal tools.
Below is a gdalinfo report of the tif.
Ideally, I want to use gdal_translate to set NODATA=-32768 but since there are other values near that like -32767 and maybe others this doesn't work. I was able to work around this issue with the following to set all values < -5 to -32768 and then asserting the NoDataValue=-32768.
Now gdalinfo on SST-out.tif report (truncated) is much more accurate WRT the actual data values:
Code:
l3mapgen interp=area projection='EPSG:3857' threshold=0.5 ofile=SST-l3mapgen-out.tif ifile=SNPP_VIIRS.20240619T204200.sst.L3b.nc oformat=tiff fudge=5.0 suite=SST product=sst apply_pal=0 quiet=0 resolution=qkmLoading default parameters from /u/ocssw//share/viirs/npp/l3mapgen_defaults.parLoading default parameters from /u/ocssw//share/common/l3mapgen_defaults_SST.parl3mapgen 2.4.0-T2024.20 (Jun 6 2024 21:11:08)ifile : SNPP_VIIRS.20240619T204200.sst.L3b.ncofile : SST-l3mapgen-out.tifoformat : tiffprojection : EPSG:3857resolution : 289.895mproduct : sstqual_prod :north : 25.974south : 2.589east : -100.127west : -125.586image size : 9342 x 977899% completeactual data min : -5.000000actual data max : 32.980000num filled pixels : 16901924percent filled pixels : 18.50%Below is a gdalinfo report of the tif.
Code:
$ gdalinfo -stats -hist SST-l3mapgen-out.tifDriver: GTiff/GeoTIFFFiles: SST-l3mapgen-out.tifSize is 9778, 9342Coordinate System is:PROJCRS["WGS 84 / Pseudo-Mercator", BASEGEOGCRS["WGS 84", ENSEMBLE["World Geodetic System 1984 ensemble", MEMBER["World Geodetic System 1984 (Transit)"], MEMBER["World Geodetic System 1984 (G730)"], MEMBER["World Geodetic System 1984 (G873)"], MEMBER["World Geodetic System 1984 (G1150)"], MEMBER["World Geodetic System 1984 (G1674)"], MEMBER["World Geodetic System 1984 (G1762)"], MEMBER["World Geodetic System 1984 (G2139)"], ELLIPSOID["WGS 84",6378137,298.257223563, LENGTHUNIT["metre",1]], ENSEMBLEACCURACY[2.0]], PRIMEM["Greenwich",0, ANGLEUNIT["degree",0.0174532925199433]], ID["EPSG",4326]], CONVERSION["Popular Visualisation Pseudo-Mercator", METHOD["Popular Visualisation Pseudo Mercator", ID["EPSG",1024]], PARAMETER["Latitude of natural origin",0, ANGLEUNIT["degree",0.0174532925199433], ID["EPSG",8801]], PARAMETER["Longitude of natural origin",0, ANGLEUNIT["degree",0.0174532925199433], ID["EPSG",8802]], PARAMETER["False easting",0, LENGTHUNIT["metre",1], ID["EPSG",8806]], PARAMETER["False northing",0, LENGTHUNIT["metre",1], ID["EPSG",8807]]], CS[Cartesian,2], AXIS["easting (X)",east, ORDER[1], LENGTHUNIT["metre",1]], AXIS["northing (Y)",north, ORDER[2], LENGTHUNIT["metre",1]], USAGE[ SCOPE["Web mapping and visualisation."], AREA["World between 85.06°S and 85.06°N."], BBOX[-85.06,-180,85.06,180]], ID["EPSG",3857]]Data axis to CRS axis mapping: 1,2Origin = (-13980489.748659253120422,2996145.823402185924351)Pixel Size = (289.894507274305511,-289.894507274305511)Metadata: AREA_OR_POINT=Area OBPG_version=UnspecifiedImage Structure Metadata: COMPRESSION=LZW INTERLEAVE=BANDCorner Coordinates:Upper Left (-13980489.749, 2996145.823) (125d35'19.95"W, 25d58'34.68"N)Lower Left (-13980489.749, 287951.336) (125d35'19.95"W, 2d35' 9.00"N)Upper Right (-11145901.257, 2996145.823) (100d 7'31.20"W, 25d58'34.68"N)Lower Right (-11145901.257, 287951.336) (100d 7'31.20"W, 2d35' 9.00"N)Center (-12563195.503, 1642048.580) (112d51'25.58"W, 14d35'25.71"N)Band 1 Block=9778x9342 Type=Float32, ColorInterp=Gray Minimum=-32767.000, Maximum=32.980, Mean=-26699.336, StdDev=12734.1140...10...20...30...40...50...60...70...80...90...100 - done. 256 buckets from -32831.3 to 97.2937: 74444152 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 16901924 Metadata: STATISTICS_MAXIMUM=32.979999542236 STATISTICS_MEAN=-26699.336323204 STATISTICS_MINIMUM=-32767 STATISTICS_STDDEV=12734.11371322 STATISTICS_VALID_PERCENT=100Code:
gdal_calc.py -A SST-l3mapgen-out.tif --outfile=SST-out.tif --calc="where(A<-5,-32768,A)" --NoDataValue=-32768 --overwriteCode:
...Corner Coordinates:Upper Left (-13980489.749, 2996145.823) (125d35'19.95"W, 25d58'34.68"N)Lower Left (-13980489.749, 287951.336) (125d35'19.95"W, 2d35' 9.00"N)Upper Right (-11145901.257, 2996145.823) (100d 7'31.20"W, 25d58'34.68"N)Lower Right (-11145901.257, 287951.336) (100d 7'31.20"W, 2d35' 9.00"N)Center (-12563195.503, 1642048.580) (112d51'25.58"W, 14d35'25.71"N)Band 1 Block=9778x1 Type=Float32, ColorInterp=Gray Min=-5.000 Max=32.980 Minimum=-5.000, Maximum=32.980, Mean=4.728, StdDev=9.999 NoData Value=-32768 Metadata: STATISTICS_MAXIMUM=32.979999542236 STATISTICS_MEAN=4.728431679632 STATISTICS_MINIMUM=-5 STATISTICS_STDDEV=9.9994284060557 STATISTICS_VALID_PERCENT=100Statistics: Posted by woodbri — Tue Jul 09, 2024 11:19 am America/New_York
