[Gdal-dev] GDAL 1.2.2 Released

Frank Warmerdam warmerdam at pobox.com
Thu Sep 16 19:08:13 EDT 2004

Eduardo Patto Kanegae wrote:

>>SQLite Driver:
>>     - New read/write driver implemented for SQLite databases.
> # it means will be possible to store POINTS tables on databases such 
 > as MySQL, Informix, MSSQL, DB2, etc a then display these data using
 > tools like MapServer ? or it will also possible to store complex
 > geometries(line/poly's)?


The above comment just refers to a driver being implemented for the SQLite
database system (http://www.sqlite.org).  It doesn't help with any of the
databases you mention.

However, OGR also has support for ODBC data connections and this has been
used to read data from a variety of RDBMS systems.  Note that the ODBC
driver has limited support for geometries from these tables, and it is
sometimes necessary to use the OGR VRT (virtual) driver as an extra
layer to indicate what fields of a table from ODBC should be used as x, y
or as well known text style geometry.

I would suggest you read up on the VRT and ODBC OGR drivers if you are
interested in this.

>>CSV Driver:
>>     - New read/write driver implemented for comma seperated value files.
> # I never used this OGR option... what is it for? it is possible to load a CVS like:
> 0;A;210.5;53
> 1;B;268;9.68
> ... and so on...

Yes, but there is no implicit knowledge in OGR that X and Y are location
information.   This would have to be interpreted by a VRT datasource
referring to the CSV datasource.

I would add that your example uses semi-colons as field seperateors.
Currently the CSV only supports _comma_ seperated value files.

>>     - Integration a series of methods utilizing GEOS when available.  Note
>>       that Intersect() is still just an envelope comparison.
> # cool... means OGR can make topological tests?

Yes. There are methods on the OGRGeometry to do various topological
tests now.  There are also methods for converting between OGR and GEOS
geometry formats if you want to use other GEOS capabilities directly.

You might want to skim the OGRGeometry method list for stuff like
Intersect(), Touches(), Overlaps(), ConvexHull(), Buffer(),
Intersection() and Difference().


Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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