Opening in stars shows that the read data are interpreted as degrees
Kelvin:
library(stars)
ss <- read_stars("MOD11A2.A2000049.h17v05.006.2015058135048.tif")
print(ss, n=1e8)
stars object with 2 dimensions and 1 attribute
attribute(s):
MOD11A2.A2000049.h17v05.006.2015058135048.tif [K]
Min. :272.1
1st Qu.:293.3
Median :296.5
Mean :296.1
3rd Qu.:298.8
Max. :309.2
NA's :926190
dimension(s):
from to offset delta refsys point values
x 1 1200 -1111951 926.625 unnamed FALSE NULL [x]
y 1 1200 4447802 -926.625 unnamed FALSE NULL [y]
The summary agrees with
library(rgdal)
o <- readGDAL("MOD11A2.A2000049.h17v05.006.2015058135048.tif")
summary(o)
Object of class SpatialGridDataFrame
Coordinates:
min max
x -1111951 0
y 3335852 4447802
Is projected: TRUE
proj4string :
[+proj=sinu +lon_0=0 +x_0=0 +y_0=0 +R=6371007.181 +units=m +no_defs]
Grid attributes:
cellcentre.offset cellsize cells.dim
x -1111487 926.6254 1200
y 3336315 926.6254 1200
Data attributes:
band1
Min. :272.1
1st Qu.:293.3
Median :296.5
Mean :296.1
3rd Qu.:298.8
Max. :309.2
NA's :926190
and
library(raster)
r <- raster("MOD11A2.A2000049.h17v05.006.2015058135048.tif")
summary(values(r))
Min. 1st Qu. Median Mean 3rd Qu. Max. NA's
272.1 293.3 296.5 296.1 298.8 309.2 926190
So my feeling is that the representation is correct in degrees Kelvin.
Others please join in, I'm not familiar with MODIS HDF data. I think
something gives the metadata in the GeoTIFF the wrong data bounds - they
do seem to be UInt16. The output of gdalinfo (command line) includes:
...
units=K
valid_range=7500, 65535
...
Band 1 Block=1200x3 Type=UInt16, ColorInterp=Gray
NoData Value=0
Unit Type: K
...
Roger
On Tue, 24 Mar 2020, Victor F. Rodriguez Galiano wrote:
Hi Roger, the link to he image is given below. This image was generated
from a .hdf file using the function gdal_translate.
gdal_translate(sds[1], dst_dataset=paste0(substr(filename, 1,
nchar(filename)-4) ,".tif", ))
https://wetransfer.com/downloads/4569e9a85c02faad5016b83d0b50217820200324084015/f2eafdfafaae74de9ac8e25017fc5cc520200324084015/e46e80
Thanks
Victor
El lun., 23 mar. 2020 a las 21:07, Roger Bivand (<roger.biv...@nhh.no>)
escribió:
Please make the file in question available for download (url), or the url
you downloaded it from (no login), on this list. It looks as though the
unsigned 16 bit integer is not right.
Roger Bivand
Norwegian School of Economics
Bergen, Norway
------------------------------
*Fra:* R-sig-Geo <r-sig-geo-boun...@r-project.org> på vegne av Victor F.
Rodriguez Galiano <vrgali...@gmail.com>
*Sendt:* mandag 23. mars 2020, 21.02
*Til:* r-sig-geo@r-project.org
*Emne:* [R-sig-Geo] issue when opening raster image in R, the pixel
values a rescaled somehow
I opened a Geotiff image in R using the raster function. However, the
image seems to be rescaled. The minimum and maximum values should be 13607
and 15461 but are 275 and 305. The Geotiff image when opened in a GIS is
correct but not in R. This is my code: Script: library(raster)
trial<-raster("MOD11A2.A2000049.h17v05.006.2015058135048.tif", datatype =
"INT2U") trial plot(trial) [[alternative HTML version deleted]]
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--
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; e-mail: roger.biv...@nhh.no
https://orcid.org/0000-0003-2392-6140
https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
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