Hi Folks, I have a 32bit NDVI image that I'm told was exported from Google Earth Engine, with possibly a trip through R along the way. In ArcGIS desktop and Qgis there are "nan" values reported for the image collar, however gdalinfo doesn't say anything about them. If I project the image in gdalwarp the output image contains both nan AND nodata. This is rather confusing.
a) Why does gdalinfo not report the presence of nan? Meaning: how do I know when I will need to invoke (b)? b) What do I need to do so that applications will use nan as nodata? Fig1: Projected output. Pink == nodata, red == 0, black == nan. Here's the file https://sft.gov.yk.ca/link/61czGFXOyyFsh387CxbTEF (255 MB, link valid for 3 months. The image is free and libre.) Gdalinfo report: Size is 14742, 6761 Coordinate System is: GEOGCRS["WGS 84", DATUM["World Geodetic System 1984", ELLIPSOID["WGS 84",6378137,298.257223563, LENGTHUNIT["metre",1]]], PRIMEM["Greenwich",0, ANGLEUNIT["degree",0.0174532925199433]], CS[ellipsoidal,2], AXIS["geodetic latitude (Lat)",north, ORDER[1], ANGLEUNIT["degree",0.0174532925199433]], AXIS["geodetic longitude (Lon)",east, ORDER[2], ANGLEUNIT["degree",0.0174532925199433]], ID["EPSG",4326]] Data axis to CRS axis mapping: 2,1 Origin = (-137.935952550438884,61.086337635411589) Pixel Size = (0.000269494585236,-0.000269494585236) Metadata: AREA_OR_POINT=Area Image Structure Metadata: COMPRESSION=LZW INTERLEAVE=BAND Corner Coordinates: Upper Left (-137.9359526, 61.0863376) (137d56' 9.43"W, 61d 5'10.82"N) Lower Left (-137.9359526, 59.2642847) (137d56' 9.43"W, 59d15'51.43"N) Upper Right (-133.9630634, 61.0863376) (133d57'47.03"W, 61d 5'10.82"N) Lower Right (-133.9630634, 59.2642847) (133d57'47.03"W, 59d15'51.43"N) Center (-135.9495080, 60.1753112) (135d56'58.23"W, 60d10'31.12"N) Band 1 Block=256x256 Type=Float32, ColorInterp=Gray Description = NDVI Min=-0.888 Max=0.992 Minimum=-0.888, Maximum=0.992, Mean=0.103, StdDev=0.141 Overviews: 7371x3381, 3686x1691, 1843x846, 922x423, 461x212 Metadata: STATISTICS_COVARIANCES=0.01992952634076865 STATISTICS_MAXIMUM=0.9921875 STATISTICS_MEAN=0.10253506184277 STATISTICS_MINIMUM=-0.88755017518997 STATISTICS_SKIPFACTORX=1 STATISTICS_SKIPFACTORY=1 STATISTICS_STDDEV=0.14117197434607 Gdalwarp command: set _opt=-co compress=zstd -co level=17 -co num_threads=all_cpus -co predictor=yes -co bigtiff=yes gdalwarp -wm 512 %_opt% -of cog -t_srs epsg:3579 -r med NDVI1984.tif t\NDVI1984.tif GDAL 3.1.4, released 2020/10/20 Thanks! Matt Wilkie Geomatics Analyst Environment | Technology, Innovation and Mapping T 867-667-8133 | http://yukon.ca/ Hours: 08:30-16:30, Tue-Wed: Office, Thu-Fri: Remote.
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