saga grid format TOPTOBOTTOM
Chuck, raster can read both TOPTOBOTTOM=FALSE and TOPTOBOTTOM=TRUE SAGA files. However, it only writes TOPTOBOTTOM=TRUE. GDAL can read and write TOPTOBOTTOM=TRUE only. Apparently QGIS has a native driver for SAGA that can only do TOPTOBOTTOM=FALSE, which is odd (as it not the common approach). Can't you force QGIS to use GDAL to read SAGA files? Another approach would be to use e.g. GTiff. If you are desperate you could also write a function to create the type QGIS needs using flip(r, 'y') and that then changes the SAGA header file to TOPTOBOTTOM=FALSE. Robert
On Mon, May 20, 2013 at 9:46 AM, Chuck Bulmer <cebulmer at telus.net> wrote:
Hi all.
I am using package raster to crop some saga grids with a shapefile.
The original inut sgrd file looks like this:
NAME = ELEV_1HA
DESCRIPTION =
UNIT =
DATAFILE_OFFSET = 0
DATAFORMAT = FLOAT
BYTEORDER_BIG = FALSE
POSITION_XMIN = 321888.3470000000
POSITION_YMIN = 376291.6470000000
CELLCOUNT_X = 15358
CELLCOUNT_Y = 13473
CELLSIZE = 100.0000000000
Z_FACTOR = 1.000000
NODATA_VALUE = -9999.000000
TOPTOBOTTOM = FALSE
After using the (below) code, the output sgrd file looks like this:
NAME = ELEV_1HA
DESCRIPTION =
UNIT =
DATAFORMAT = FLOAT
DATAFILE_OFFSET = 0
BYTEORDER_BIG = FALSE
POSITION_XMIN = 1427688.347
POSITION_YMIN = 486091.647
CELLCOUNT_Y = 1685
CELLCOUNT_X = 784
CELLSIZE = 100
Z_FACTOR = 1.000000
NODATA_VALUE = -3.4e+38
TOPTOBOTTOM = TRUE
The resulting files are read by SAGA-GIS with no problem and they look good,
but I want to use Quantum GIS as my map viewer and when I try to load the
result file into QGIS it provides me with the following error:
"..ELEV_1HA is not a supported data source. Currently the Saga Binary Grid
driver does not support Saga Grids written TOPTOBOTTOM"
If I load and resave the grid with SAGA, TOPTOBOTTOM reverts back to FALSE,
and the grid can be read by QGIS, but I'd like to avoid this extra step.
Is there a way to add a setting to the crop function? raster? gdal? to write
as TOPTOBOTTOM=FALSE, which would save me the extra step of loading and
resaving each grod.
Thanks for any help you can provide
Chuck
Here's the code ... (Windows 7x64)
s <- raster("D:\\BC_DSM\\ELEV_1HA.sdat")
t<- shapefile("D:\\BC_DSM\\ecodistrict_bdy_b10k.shp")
crop(s,t,filename="D:\\BC_DSM\\Results\\ELEV_1HA.sdat")
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