On Fri, 21 Aug 2009, Roger Bivand wrote:
On Fri, 21 Aug 2009, Frank Warmerdam wrote:
Roger Bivand wrote:
Hi,
The code for the LAN/GIS driver uses GDT_Int16 for Pixel type 2, rather
than GDT_UInt16. Is this justified? A user of rgdal has a case of unsigned
16-bit data stored by "a forest landscape model", being treated by the
driver as signed. The header does not seem to have a signed/unsigned flag.
Is this a problem of ambiguity in use of a (closed?) specification, or
should the driver be using GDT_UInt16?
I'm asking on the list first, because this may be ambiguity, not a bug.
Roger,
The only specification information I have on the format does not indicate
whether 16bit values should be treated as signed or unsigned. If you are
confident that it should be treated as unsigned file a ticket and we will
fix it - hopefully this won't just break it for someone else!
Frank,
Thanks, I'm waiting to receive the affected file. I'll let you know when I've
got it.
(reverting to list)
Correction, the user reported that:
Apparently, gdalinfo retrieves the correct min, max, and statistics,
despite the use of GDT_Int16.
on his Windows platform. The different GDAL versions ought to explain why
his gdalinfo says Int16 but gives statistics from UInt16.
He has:
From FWTools:
gdalinfo --version
GDAL 1.7.0dev, FWTools 2.4.2 released 2009/06/24
C:\Program Files\FWTools2.4.2>gdalinfo stand_bm.gis
Driver: LAN/Erdas .LAN/.GIS
Files: c:\landis\harvest_problem\FTT-N_MinT-N\stand_bm.gis
c:\landis\harvest_problem\FTT-N_MinT-N\stand_bm.gsw
Size is 1758, 839
Coordinate System is:
LOCAL_CS["Unknown",
UNIT["Meter",1]]
Origin = (33773.261718750000000,945478.062500000000000)
Pixel Size = (100.000000000000000,-100.000000000000000)
Corner Coordinates:
Upper Left ( 33773.262, 945478.063)
Lower Left ( 33773.262, 861578.063)
Upper Right ( 209573.262, 945478.063)
Lower Right ( 209573.262, 861578.063)
Center ( 121673.262, 903528.063)
Band 1 Block=1758x1 Type=Int16, ColorInterp=Undefined
Min=0.000 Max=48499.000
Minimum=0.000, Maximum=48499.000, Mean=12833.830, StdDev=13635.800
Metadata:
STATISTICS_MINIMUM=0
STATISTICS_MAXIMUM=48499
STATISTICS_MEAN=12833.830260712
STATISTICS_MEDIAN=8.7254821994872e-239
STATISTICS_MODE=3.9864100424366e-293
STATISTICS_STDDEV=13635.800289332
LAYER_TYPE=thematic
rgdal_0.6-12
getGDALVersionInfo()
[1] "GDAL 1.6.1, released 2009/05/11"
For me on x86_64, GDALinfo() in rgdal and 1.6.2 gdalinfo -stats agree.
$ gdalinfo -stats stand_bm.gis
Driver: LAN/Erdas .LAN/.GIS
Files: stand_bm.gis
Size is 1758, 839
Coordinate System is:
LOCAL_CS["Unknown",
UNIT["Meter",1]]
Origin = (33773.261718750000000,945478.062500000000000)
Pixel Size = (100.000000000000000,-100.000000000000000)
Corner Coordinates:
Upper Left ( 33773.262, 945478.062)
Lower Left ( 33773.262, 861578.062)
Upper Right ( 209573.262, 945478.062)
Lower Right ( 209573.262, 861578.062)
Center ( 121673.262, 903528.062)
Band 1 Block=1758x1 Type=Int16, ColorInterp=Undefined
Minimum=-32140.000, Maximum=29620.000, Mean=8315.507, StdDev=13186.107
Metadata:
STATISTICS_MINIMUM=-32140
STATISTICS_MAXIMUM=29620
STATISTICS_MEAN=8315.5065072863
STATISTICS_STDDEV=13186.10731815
On the trunk, GDT_Int16 is used too, so how does gdalinfo detect that it
is actually UInt16?
Roger
Best wishes,
Roger
Best regards,
--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: roger.biv...@nhh.no
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