[Qgis-user] [EXTERNAL] Re: Working with second band of two-band GeoTIFF

[Fielding, Eric J (329A)]

Alex,

Here is the output of gdalinfo on the file:
======
gdalinfo filt_topophase.unw.geo.tif
Driver: GTiff/GeoTIFF
Files: filt_topophase.unw.geo.tif
Size is 4866, 6076
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"]]
Origin = (104.507222222222225,28.770277777777778)
Pixel Size = (0.000277777777778,-0.000277777777778)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left  ( 104.5072222,  28.7702778) (104d30'26.00"E, 28d46'13.00"N)
Lower Left  ( 104.5072222,  27.0825000) (104d30'26.00"E, 27d 4'57.00"N)
Upper Right ( 105.8588889,  28.7702778) (105d51'32.00"E, 28d46'13.00"N)
Lower Right ( 105.8588889,  27.0825000) (105d51'32.00"E, 27d 4'57.00"N)
Center      ( 105.1830556,  27.9263889) (105d10'59.00"E, 27d55'35.00"N)
Band 1 Block=512x512 Type=Float32, ColorInterp=Gray
  NoData Value=0
  Overviews: 2433x3038, 1217x1519, 609x760, 305x380, 153x190
Band 2 Block=512x512 Type=Float32, ColorInterp=Undefined
  NoData Value=0
  Overviews: 2433x3038, 1217x1519, 609x760, 305x380, 153x190
===========

I can see that band two has ColorInterp=Undefined. I don't know what that means.

The GeoTIFF file is automatically generated by some SAR interferometry processing scripts we have and it is over 300 MB. The direct link to the file is:
http://hysds-urgent-response.s3-us-west-2.amazonaws.com/datasets/interferogram/v1.2/2019/06/09/S1-IFG_RM_M1S2_TN055_20190621T110015-20190609T105947_s1-resorb-1ea6-v1.2-china/merged/filt_topophase.unw.geo.tif

Thanks,
	++Eric

-----Original Message-----
From: Alex M <tech_dev at wildintellect.com>

    On 6/23/19 11:11, Fielding, Eric J (329A) wrote:
    > I only recently switched to QGIS 3, so I am not sure whether I am missing something that was moved to a different place or the handling of raster layers changed. I am using 3.6.0 on a Mac. I have a two-band GeoTIFF image, and I want to run the Raster Calculator on the second band of the image. When I open the Raster Calculator, it only shows me band 1 of the image (image_name at 1). I tried forcing it to use band 2 with @2, but that did not work. I looked at layer Export->Save As and I don’t see a way to save the second band there. I finally went to the terminal and used “gdal_translate -b 2” to save the second band to a separate file. In QGIS 2, it showed me the two bands of the image in the Raster Calculator. Is there a way to do this inside QGIS 3?
    > 
    
    Eric,
    
    Can you provide a sample 2 band raster file?
    Also what does the Information tab in the layer Properties show (should
    be similar to gdalinfo)?
    
    I'm wondering if it thinks your 2nd band is an Alpha/Mask layer and
    treats it differently.
    
    Thanks,
    Alex