Dylan Beaudette wrote:
Hi,
I am not sure if this is a DBF issue, or something deeper in OGR, but there
does not appear to be a mechanism for preserving 'nodata' or NULL values when
exporting from GRASS to vector formats through v.out.ogr.
...
It seems that on export via OGR there is some kind of mangline of nodata. This
issue is a serious problem anytime you need to move vector data between
applications, through the use of an intermediate file (usually a shapefile).
Any ideas on what could be causing this problem? Fixing it would solve several
important issues. If need be I will file a new ticket on the topic.
Relevent tickets?
http://trac.osgeo.org/gdal/ticket/809
http://trac.osgeo.org/gdal/ticket/528
Dylan,
Generally speaking OGR understands about null attribute values, though
there may be no way to represent them in some formats. They should work
fine in shapefile format though.
Reviewing the mk_att() function in v.out.ogr's main.c I don't see
any effort to distinguish between null and non-null attributes so
I think the problem is just a limitation of v.out.ogr. If possible,
I'd suggest fixing it there.
Best regards,
--
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I set the clouds in motion - turn up | Frank Warmerdam, [EMAIL PROTECTED]
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and watch the world go round - Rush | Geospatial Programmer for Rent
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