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Landsat 5 values change from normal NDVI -1 to 1 when created in Multispec as a 32 bit signed data image. When adding the raster layer in QGIS, the value range changed to 0-255. How does one properly export the image from Multispec into QGIS to maintain pixel values obtained in Multispec?

After TOA and DOS1 were applied to the raw data, red and near infrared bands values ranged between 0.007 and 0.818.

AREA_OR_POINT=Area
TIFFTAG_IMAGEDESCRIPTION=Generated by MultiSpecWin32_12.17.2014 on 07-29-2015 19:12:31 |
TIFFTAG_RESOLUTIONUNIT=1 (unitless)
TIFFTAG_XRESOLUTION=1
TIFFTAG_YRESOLUTION=1
Band 1
STATISTICS_MAXIMUM=255
STATISTICS_MEAN=79.410480872596
STATISTICS_MINIMUM=0
STATISTICS_STDDEV=65.984417579303
Dimensions
X: 781 Y: 748 Bands: 1
Origin
654045,5.84688e+06
Pixel Size
30,-30
No Data Value
*NoDataValue not set* 
Data Type
Byte - Eight bit unsigned integer
Pyramid overviews
Layer Spatial Reference System
+proj=utm +zone=18 +south +datum=WGS84 +units=m +no_defs
Layer Extent (layer original source projection)
654045.0000000000000000,5824435.0000000000000000 : 677475.0000000000000000,5846875.0000000000000000
Band
Band 1
Band No
1
No Stats
No stats collected yet 
  • 1
    Can you edit your question again to provide the following information please. What format is the output raster? How did you export it from multispec? Can you provide a gdalinfo report/QGIS metadata properties (open the layer properties from QGIS, click the metadata entry and then scroll down to the properties box, copy that into your question) please. – user2856 Jul 30 '15 at 4:51
  • 1
    Thank you for adding that extra information. But you still have not added all the information I suggested - i.e how did you export it from multispec?. However, I can see from that extra information that QGIS has not altered your image. You exported it from multispec (somehow...) as 8-bit unsigned (Byte) format which has data range of 0-255. You have either used the "Processor->Reformat->Change Image File Format" menu and used 8-bit unsigned as the data type, or you have used "File->Save Image To GeoTIFF As..." which only exports in 8-bit... – user2856 Jul 31 '15 at 4:06
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Use the "Processor->Reformat->Change Image File Format" menu. Select 32 (or 64) bit Real data type. If you are generating NDVI from a multispectral image at this stage, tick the "Transform Data" checkbox and select "New Channel from General Algebraic Transformation" and input the NDVI calculation. Click OK and enter your output TIFF filename in the dialog and click Save.

enter image description here

Output NDVI GeoTIFF derived from the sample dataset included with Multispec:

gdalinfo -stats TipJul1_NDVI.tif
Driver: GTiff/GeoTIFF
Files: TipJul1_NDVI.tif
Size is 169, 169
Coordinate System is:
PROJCS["NAD27 / UTM zone 16N",
    GEOGCS["NAD27",
        DATUM["North_American_Datum_1927",
            SPHEROID["Clarke 1866",6378206.4,294.9786982139006,
                AUTHORITY["EPSG","7008"]],
            AUTHORITY["EPSG","6267"]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433],
        AUTHORITY["EPSG","4267"]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",-87],
    PARAMETER["scale_factor",0.9996],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AUTHORITY["EPSG","26716"]]
Origin = (491971.250000000000000,4490264.250000000000000)
Pixel Size = (28.500000000000000,-28.500000000000000)
Metadata:
  AREA_OR_POINT=Area
  TIFFTAG_IMAGEDESCRIPTION=Generated by MultiSpecWin32_02.12.2015 on 08-03-2015  12:00:28 |
  TIFFTAG_RESOLUTIONUNIT=1 (unitless)
  TIFFTAG_XRESOLUTION=1
  TIFFTAG_YRESOLUTION=1
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (  491971.250, 4490264.250) ( 87d 5'41.43"W, 40d33'54.04"N)
Lower Left  (  491971.250, 4485447.750) ( 87d 5'41.21"W, 40d31'17.83"N)
Upper Right (  496787.750, 4490264.250) ( 87d 2'16.60"W, 40d33'54.16"N)
Lower Right (  496787.750, 4485447.750) ( 87d 2'16.52"W, 40d31'17.95"N)
Center      (  494379.500, 4487856.000) ( 87d 3'58.94"W, 40d32'36.01"N)
Band 1 Block=169x169 Type=Float32, ColorInterp=Gray
  Minimum=-0.097, Maximum=0.755, Mean=0.536, StdDev=0.138
  Metadata:
    STATISTICS_MAXIMUM=0.75510203838348
    STATISTICS_MEAN=0.53583352091529
    STATISTICS_MINIMUM=-0.096774190664291
    STATISTICS_STDDEV=0.13781631611306

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