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Also known as Geographic Markup Language and GML/XML. GML is a text-based, XML format that can represent vector and attribute data. This is an Open Geospatial Consortium specification for data interchange. More information is available at http://www.opengeospatial.org/standards/gml
GML files are usually a single text file with a GML filename extension. Some may use XML as the filename extension:
coal_dep.gml
XML schema documents often accompany GML files that have been translated from some other format (e.g. using the ogr2ogr utility).
GML uses sets of nested tags to define attributes and geometry coordinates. Example of text in a GML file:
<gml:featureMember>
<Coal_Deposits fid="1">
<UNKNOWN>0.000</UNKNOWN>
<NA>0.000</NA>
<ID>2</ID>
<ID2>2</ID2>
<MARK>7</MARK>
<COALKEY>110</COALKEY>
<COALKEY2>110</COALKEY2>
<ogr:geometryProperty>
<gml:Point>
<gml:coordinates>78.531,50.694</gml:coordinates>
</gml:Point>
</ogr:geometryProperty>
</Coal_Deposits>
</gml:featureMember>
Using ogrinfo on a single GML file:
> ogrinfo /data/gml/coal_dep.gml
Had to open data source read-only.
INFO: Open of `coal_dep.gml'
using driver `GML' successful.
1: Coal_Deposits
Using ogrinfo to examine the structure of one layer:
> ogrinfo -summary /data/gml/coal_dep.gml Coal_Deposits
Had to open data source read-only.
INFO: Open of `coal_dep.gml'
using driver `GML' successful.
Layer name: Coal_Deposits
Geometry: Unknown (any)
Feature Count: 266
Extent: (23.293650, 37.986340) - (179.272550, 80.969670)
Layer SRS WKT:
(unknown)
UNKNOWN: Real (0.0)
NA: Real (0.0)
ID: Integer (0.0)
ID2: Integer (0.0)
MARK: Integer (0.0)
COALKEY: Integer (0.0)
COALKEY2: Integer (0.0)
LONG: Real (0.0)
LAT: Real (0.0)
Map File Example:
LAYER
NAME coal_deposits
TYPE POINT
STATUS DEFAULT
CONNECTIONTYPE OGR
CONNECTION "gml/coal_dep.gml"
CLASS
STYLE
COLOR 0 0 0
SYMBOL 'circle'
SIZE 6
END
END
END