QGIS » QGIS Application

Lene Fischer wrote:

When opening a singe file - the min/max is not loaded correct.
Link to data http://ku-gis.dk/blog/wp-content/uploads/2016/05/dtm_1km_6183_693.zip

confirmed (but the description/title is about VRT files, so this may need a separate ticket, agree?).

giovanni@sibirica:~/Desktop/dtm_1km_6183_693 > gdalinfo -mm dtm_1km_6183_693.tif
Driver: GTiff/GeoTIFF
Files: dtm_1km_6183_693.tif
Size is 2500, 2500
Coordinate System is:
PROJCS["ETRS89 / UTM zone 32N",
    GEOGCS["ETRS89",
        DATUM["European_Terrestrial_Reference_System_1989",
            SPHEROID["GRS 1980",6378137,298.2572221010002,
                AUTHORITY["EPSG","7019"]],
            TOWGS84[0,0,0,0,0,0,0],
            AUTHORITY["EPSG","6258"]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433],
        AUTHORITY["EPSG","4258"]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",9],
    PARAMETER["scale_factor",0.9996],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AUTHORITY["EPSG","25832"]]
Origin = (693000.000000000000000,6184000.000000000000000)
Pixel Size = (0.400000000000000,-0.400000000000000)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  COMPRESSION=DEFLATE
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (  693000.000, 6184000.000) ( 12d 4'34.68"E, 55d45'47.20"N)
Lower Left  (  693000.000, 6183000.000) ( 12d 4'32.13"E, 55d45'14.90"N)
Upper Right (  694000.000, 6184000.000) ( 12d 5'31.97"E, 55d45'45.76"N)
Lower Right (  694000.000, 6183000.000) ( 12d 5'29.41"E, 55d45'13.46"N)
Center      (  693500.000, 6183500.000) ( 12d 5' 2.05"E, 55d45'30.33"N)
Band 1 Block=256x256 Type=Float32, ColorInterp=Gray
    *Computed Min/Max=-0.238,5.437*
  NoData Value=-9999

Lene Fischer wrote:

Yes

Hi Lene,
it seems there is "no issue" after all.

QGIS by default computes min/max using by default an accuracy that is set to "estimated (faster)" and this gives "wrong" results, but if you switch to "Actual (slower)" then the values are the same as gdalinfo (both for single files or vrt rasters).

I think that we can argue why using "estimated" by default and why this give min/max values that are so different (at least in cases as your dataset) from real values. I guess we have to choose another title/description for this ticket if decide that this is indeed worth to be left open.

Note:
at this point #14853 is another issue: in the histogram graph min/max markers/graph are always set to the values computed as "estimated" even if the numeric values are the ones computed as "actual".