Changes between Version 4 and Version 5 of FAQVector

Timestamp:

Oct 15, 2007, 12:33:54 PM (17 years ago)

Author:

warmerdam

Comment:

add splitting geometry types into separate shapefiles example

FAQVector

@@ -37 +37 @@
 }}}
 
+== How do I translate a mixed geometry file to shapefile format? ==
+
+Some formats (such as ESRI Shapefiles) only allow one type of geometry in 
+a layer, while other formats (such as DGN, MapInfo, GML) allow a mixture of
+geometry types within a single layer.  Direct attempts to translate result
+in errors like this:
+
+{{{
+% ogr2ogr out.shp mixed.dgn 
+ERROR 1: Attempt to write non-linestring (POLYGON) geometry to ARC type shapefile.
+ERROR 1: Terminating translation prematurely after failed
+translation of layer elements
+}}}
+
+The first step in dealing with such a problem is to discover what 
+geometry types exist in the source file.  For a DGN file called
+mixed.dgn, with a layer called elements this can be accomplished 
+using the following OGR SQL command (see 
+[http://www.gdal.org/ogr/ogr_sql.html OGR SQL] tutorial for details): 
+
+{{{
+% ogrinfo -ro mixed.dgn -sql 'select distinct ogr_geometry from elements'
+INFO: Open of `mixed.dgn'
+      using driver `DGN' successful.
+
+Layer name: elements
+Geometry: Unknown (any)
+Feature Count: 1
+Layer SRS WKT:
+(unknown)
+ogr_geometry: String (0.0)
+OGRFeature(elements):0
+  ogr_geometry (String) = LINESTRING
+
+OGRFeature(elements):1
+  ogr_geometry (String) = POLYGON
+
+OGRFeature(elements):2
+  ogr_geometry (String) = POINT
+}}}
+
+This file has point, line and polygon geometries.  Each will need to be 
+translated to a separate output file.  
+
+{{{
+% ogr2ogr out_point.shp mixed.dgn -where 'ogr_geometry = "POINT"'
+% ogr2ogr out_line.shp mixed.dgn -where 'ogr_geometry = "LINESTRING"'
+% ogr2ogr out_poly.shp mixed.dgn -where 'ogr_geometry = "POLYGON"'
+}}}
+
+
+