Raster mask query troubleshooting

[knutole]

The blue and red graph should be the same, but they differ with 0-10% depending on day.

Elimination of possible error sources

• Correct SRID of raster. The raster is in correct SRID. Vector mask is transformed correctly from 4326 to 3857, and vector- and raster mask yield same result. Also, all rasters are gdal_transformed to SRID 3857 on import.
• Correct pixel values of raster. Since vector- and raster mask yield same results, there's likely nothing wrong with the raster mask per se.
• Correct pixel scale of raster. The scale differ between the mask and the snow-rasters.
• Calculation. Adding the SCF_0.tif, SCF_160.tif, SCF_200.tif yield correct graph calculations of respectively 0%, 60%, 100%, which means there's nothing wrong with the calc method.
  
• Include correct values in calculation. Values 100-200 are included, which has been thrice confirmed by Eirik.
• Use float numbers. Still same results.
• IMPROVEMENT: Only use part of mask which have values > 0.
  Darkest red line is with 0 values of mask excluded.
  
• Vannmaske. Count the 20 values...

Suspicions

The difference between G—/Systemapic calcs is the least when there's most snow (ref. 20th Jan).

• If the mask was faulty (say, wrong SRID), then this would have the least effect when there's a lot of snow (with coverage going all the say to the coast, for example, and lots of area being 100%).
• So this perhaps indicates that there's something wrong - not with the calculation - but with the mask (or the watermask, perhaps).

[knutole]

gdalinfo of rasters, before import

Rasters are gdal_warped before import, gdalwarp -t_srs EPSG:3857 ${S_SRS} ${INPUTRASTERFILE} ${RASTERFILE}

gdalinfo of mask:

Driver: GTiff/GeoTIFF
Files: AgderEnergi_nodata.tif
Size is 290, 420
Coordinate System is:
PROJCS["WGS 84 / UTM zone 33N",
    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"]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",15],
    PARAMETER["scale_factor",0.9996],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AUTHORITY["EPSG","32633"]]
Origin = (-1730.000000000000000,6684402.000000000000000)
Pixel Size = (500.000000000000000,-500.000000000000000)
Metadata:
  AREA_OR_POINT=Area
  TIFFTAG_XRESOLUTION=100
  TIFFTAG_YRESOLUTION=100
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (   -1730.000, 6684402.000) (  5d59'21.41"E, 59d59'18.67"N)
Lower Left  (   -1730.000, 6474402.000) (  6d28' 5.41"E, 58d 7'28.73"N)
Upper Right (  143270.000, 6684402.000) (  8d34'13.56"E, 60d 8'24.43"N)
Lower Right (  143270.000, 6474402.000) (  8d54'52.97"E, 58d15'55.70"N)
Center      (   70770.000, 6579402.000) (  7d29'20.76"E, 59d 8' 9.71"N)
Band 1 Block=290x28 Type=Byte, ColorInterp=Gray
  NoData Value=0

gdalinfo of snow-raster:

Driver: GTiff/GeoTIFF
Files: /home/ftp_g/2016/SCF_MOD_20160101.tif
Size is 2401, 3101
Coordinate System is:
PROJCS["WGS 84 / UTM zone 33N",
    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"]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",15],
    PARAMETER["scale_factor",0.9996],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AUTHORITY["EPSG","32633"]]
Origin = (-58556.000000000000000,7973755.000000000000000)
Pixel Size = (500.000000000000000,-500.000000000000000)
Metadata:
  AREA_OR_POINT=Area
  TIFFTAG_IMAGEDESCRIPTION=Virtual mosaic (2011.06.29-modland.mos)

BandNames:
Band 1
  TIFFTAG_RESOLUTIONUNIT=1 (unitless)
  TIFFTAG_XRESOLUTION=1
  TIFFTAG_YRESOLUTION=1
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (  -58556.000, 7973755.000) (  0d41'34.60"W, 71d12'35.04"N)
Lower Left  (  -58556.000, 6423255.000) (  5d38' 8.21"E, 57d36'12.93"N)
Upper Right ( 1141944.000, 7973755.000) ( 32d54' 6.85"E, 71d 0'18.98"N)
Lower Right ( 1141944.000, 6423255.000) ( 25d44'10.52"E, 57d29'35.80"N)
Center      (  541694.000, 7198505.000) ( 15d52'52.16"E, 64d54'29.23"N)
Band 1 Block=256x256 Type=Byte, ColorInterp=Gray
  NoData Value=255