Opened 22 years ago
Last modified 22 years ago
#150 closed defect (fixed)
A/I ASCII Grid - header problems.
Reported by: | warmerdam | Owned by: | dron |
---|---|---|---|
Priority: | high | Milestone: | |
Component: | default | Version: | unspecified |
Severity: | normal | Keywords: | |
Cc: |
Description
Dear list, I found out, that r.in.gdal has some problems with importing asc-grid-files. It is not really a problem, but r.in.gdal is abit picky about the order of the header columns. If the order of the header is different, it bails out and does not import. This one does NOT work: GRASS:~/tmp/data > less qtotal.asc |head -6 yllcorner 5680384 xllcorner 3338768 nrows 3244 ncols 3400 cellsize 100 NODATA_value -9999 But this one does: GRASS:~/tmp/data > less qtotal.asc |head -6 ncols 3400 nrows 3244 xllcorner 3338768 yllcorner 5680384 cellsize 100 NODATA_value -9999 When I change the order, everything is fine. I cannot tell you where the grid-file is exported from, but I guess from some ersi-products.... Arcview itself imports without trouble. cheers steph
Change History (10)
comment:2 by , 22 years ago
> I would like output support for grids implemented. Do you have access > to an Arc/Info w/grid license that you could use to test such a thing? I havn't permenent access to Arc/Info, but I will try to implement grid writing and find a suitable Arc/Info installation for test purposes.
comment:4 by , 22 years ago
Writing of ASCII Grid files implemented with CreateCopy() function. Not commited yet because I have two questions: 1. Should Create() function also be implemented? 2. Should we write a ".prj" file along with AAIGrig file? Maybe it should be controlled by option?
comment:5 by , 22 years ago
1) Don't implement a Create() method. It isn't necessary and is hard to implement properly for formats like ascii grids. 2) Write the .prj file if a non-empty projection is available.
comment:6 by , 22 years ago
Frank, It seems I need to implement OGRSpatialReference::exportToESRI() function. I can deduce .prj file format from the OGRSpatialReference::importFromESRI() function, but maybe you know if .prj file format description exists somewhere?
comment:7 by , 22 years ago
Andrey, I am in no hurry to support "old arc/info .prj" file format for export. Just use OGRSpatialReference.morphToEsri() and then exportToWkt() and write that to the .prj file. This should work with Arc8 (which uses an ESRI variant on WKT) and folks with Arc/Info 7 can just delete the .prj file and redefine it themselves.
comment:8 by , 22 years ago
Now AAGrid driver will write a .prj file. Last question: do we have a universal mechanism for 'no data' values handling? Such values may be used in ASCII grids.
comment:9 by , 22 years ago
Formats supporting nodata values should implement the GetNoDataValue() and SetNoDataValue() methods. Note that pbSuccess should be set to FALSE if there is nodata value for a format. Some applications, such as OpenEV, will mark all "nodata" areas to transparent.
comment:10 by , 22 years ago
> Note that pbSuccess should be set to FALSE if > there is nodata value for a format. Do you mean `if there is _no_ nodata value' ? I have implement nodata handling in such way. Writing support finished, but not tested with Arc/Info, because I havn't access to this software right now. I shall test it in nearest time.
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