Thank you Barry and Robert
This is all very interesting. When I use the FWTools Shell and the
gdalinfo command it says that the Min value is zero (see below) and max
is 48499. This is different than the summary in Rgdal, which produced
the negative values. So I guess the problem is in the Rgdal.
Also, when I try Robert's proposed fix:
stnd <- raster("stand_bm.gis", values = T)
stnd[stnd < 0] <- stnd[stnd < 0] + 66535
It creates an entirely new map (i.e. one with brand new values at the
high end of the range)
So, I'm still awfully confused. Any further help would be deeply
appreciated.
Thanks Jonathan
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
----
On Thu, Aug 20, 2009 at 6:58 AM, Jonathan
Thompson<[email protected]> wrote:
Dear List,
I use a forest landscape model, which produces 16 bit unsigned ".gis" raster
files. I often read and manipulate them using rgdal and the raster package
in R.
However, sometimes, when I read in a unsigned 16 bit .gis, I get the
following:
stnd <- raster("stand_bm.gis", values = T)
summary(stnd)
Cells: 1474962
NAs : 0
Values Min. -32140
1st Qu. 0
Median 0
Mean 8316
3rd Qu. 19180
Max. 29620
Where are these negative values coming from? Opening the same file in
ArcGIS confirms what I know to be true:
Pixel Type = unsigned integer
Pixel Depth = 16 bit
Min = 0
Max = 48499
Is there anyway to force raster (or RGDAL) to treat it like an unsigned
integer?
Thank you,
Jonathan Thompson
Harvard Forest
Harvard University
Petersham, MA 01366
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