[gdal-dev] ogr2ogr - geojson to mapInfo - size of .dat become too big

[Even Rouault]

Le mercredi 23 septembre 2015 14:54:58, Maxime Demers a écrit :
> Thank you for your answer.
> 
> That works correctly with the correct layer name. However, I wonder where
> in the geojson that layer name is stored? It's not written in the file
> itself and I can't find it in the metadata of the file neither. The layer
> name I found is OGRGeoJSON. Is this a default layer name for geojson? Is it
> possible to modify it? I cannot find a place in the geojson specifications
> where they mention layer name.

It's hardcoded in the driver. There's no such thing as a layer name in the 
geojson spec. It's an implementation choice in OGR.
You can add -nln a_new_layer_name to ogr2ogr

> 
> 
> On Wed, Sep 23, 2015 at 8:43 AM, Even Rouault <even.rouault at spatialys.com>
> 
> wrote:
> > Le mercredi 23 septembre 2015 14:41:53, Maxime Demers a écrit :
> > > Hi Even,
> > > 
> > > Thank you for the suggestion. However, it seems I cannot use such a
> > > -sql statement on a geojson file. I got the following error with the
> > > command below:
> > > 
> > > ogr2ogr -f "MapInfo File" test.tab points.geojson -sql "select cast(id
> > > as integer(10)), cast(codecs as character(3)), cast(codeSecteur as
> > > character(20)), cast(codeWork as character(20)), cast(codePostal as
> > > character(6)) from points"
> > > 
> > > ERROR 1: SELECT from table points failed, no such table/featureclass.
> > 
> > The error message gives a hint of the reason of the error. There's no
> > table/layer named "points" in the source file. Do "ogrinfo
> > points.geojson" to
> > see the name of the layer.
> > 
> > > However, I have no problem to use the same command to convert a MapInfo
> > > File to another MapInfo File with the -sql statement. Are you able to
> > > confirm if its possible to do a -sql statement on a geojson file and if
> > > yes, do you know why I got this error?
> > > 
> > > thank you,
> > > 
> > > Maxime Demers
> > > 
> > > On Tue, Sep 22, 2015 at 2:47 PM, Even Rouault <
> > 
> > even.rouault at spatialys.com>
> > 
> > > wrote:
> > > > Le mardi 22 septembre 2015 16:07:56, Maxime Demers a écrit :
> > > > > Hi,
> > > > > 
> > > > > I have notice something bad when converting a geojson to mapInfo
> > > > > tab with ogr2ogr. The .dat which contain the table feature's
> > > > > properties
> > 
> > is
> > 
> > > > > getting way too big after conversion.
> > > > > 
> > > > > To test, I have converted a mapInfo tab to geojson using:
> > > > > 
> > > > > ogr2ogr -f "GeoJSON" test.geojson test.tab
> > > > > 
> > > > > and then I converted it back to mapInfo tab using:
> > > > > 
> > > > > ogr2pgr -f "MapInfo File" test2.tab test.geojson
> > > > > 
> > > > > Before convertion, the .dat of the mapInfo file was 8,75 Mo after
> > > > > conversion it became 105 Mo.
> > > > > I dont know if the problem is only when converting geojson to
> > > > > mapInfo
> > > > 
> > > > tab.
> > > > 
> > > > > What could be the cause of the problem and does a solution exists?
> > > > 
> > > > Maxime,
> > > > 
> > > > The issue is that when converting from GeoJSON to .tab, the source
> > > > text fields in GeoJSON have no longer an explicit field width, hence
> > > > the mapinfo driver fallbacks to 254 characters.
> > > > 
> > > > You could workaround with a statement like this :
> > > > 
> > > > ogr2ogr  -f "MapInfo File" test2.tab test.geojson -sql "select
> > > > cast(field1_name as character(field_width)), cast(field2_name as
> > > > character(field2_width)), ... from layername"
> > > > 
> > > > to specify explicit field width.
> > > > 
> > > > It would have been great if ogr2ogr had a mode to automate this (I
> > > > thought there was one already, but can't find it)
> > > > 
> > > > Even
> > > > 
> > > > --
> > > > Spatialys - Geospatial professional services
> > > > http://www.spatialys.com
> > 
> > --
> > Spatialys - Geospatial professional services
> > http://www.spatialys.com

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