issue when opening raster image in R, the pixel values a rescaled somehow

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.Bivand at nhh.no>)
escribi?:

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-bounces at r-project.org> p? vegne av Victor F.
Rodriguez Galiano <vrgaliano at gmail.com>
*Sendt:* mandag 23. mars 2020, 21.02
*Til:* r-sig-geo at 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]]