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saga grid format TOPTOBOTTOM

2 messages · Chuck, Robert J. Hijmans

Original
Chuck
# 
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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7 days later
Robert J. Hijmans
# 
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: