GPX (the GPS Exchange Format) is a light-weight XML data format for the interchange of GPS data (waypoints, routes, and tracks) between applications and Web services on the Internet.
OGR has support for GPX reading (if GDAL is build with expat library support) and writing.
Version supported are GPX 1.0 and 1.1 for reading, GPX 1.1 for writing.
The OGR driver supports reading and writing of all the GPX feature types :
In addition to its GPX attributes, each route point of a route has a route_fid
(foreign key to the FID of its belonging route)
and a route_point_id which is its sequence number in the route.
The same applies for track points with track_fid, track_seg_id and track_seg_point_id. All coordinates are relative to the WGS84 datum (EPSG:4326).
If the environment variable GPX_ELE_AS_25D is set to YES, the elevation element will be used to set the Z coordinates of waypoints, route points and track points.
The OGR/GPX reads and writes the GPX attributes for the waypoints, routes and tracks.
By default, up to 2 <link> elements can be taken into account by feature. This default number can be changed with the GPX_N_MAX_LINKS environment variable.
The content returned by OGR will be encoded in UTF-8, after the conversion from the encoding mentionned in the file header is.
If your GPX file is not encoded in one of the previous encodings, it will not be parsed by the
GPX driver. You may convert it into one of the supported encoding with the iconv utility
for example and change accordingly the encoding parameter value in the XML header.
When writing a GPX file, the driver expects UTF-8 content to be passed in.
The following sequence GPX content :
<extensions> <navaid:name>TOTAL RF</navaid:name> <navaid:address>BENSALEM</navaid:address> <navaid:state>PA</navaid:state> <navaid:country>US</navaid:country> <navaid:frequencies> <navaid:frequency type="CTAF" frequency="122.900" name="CTAF"/> </navaid:frequencies> <navaid:runways> <navaid:runway designation="H1" length="80" width="80" surface="ASPH-G"> </navaid:runway> </navaid:runways> <navaid:magvar>12</navaid:magvar> </extensions>will be interpreted in the OGR SF model as :
navaid_name (String) = TOTAL RF navaid_address (String) = BENSALEM navaid_state (String) = PA navaid_country (String) = US navaid_frequencies (String) = <navaid:frequency type="CTAF" frequency="122.900" name="CTAF" ></navaid:frequency> navaid_runways (String) = <navaid:runway designation="H1" length="80" width="80" surface="ASPH-G" ></navaid:runway> navaid_magvar (Integer) = 12
Note : the GPX driver will output content of the extensions element only if it is found in the first records of the GPX file. If extensions appear later, you can force an explicit parsing of the whole file with the GPX_USE_EXTENSIONS environment variable.
If the output file already exits, the writing will not occur. You have to delete the existing file first.
Supported geometries :
For route points and tracks points, if there is a Z coordinate, it is used to fill the elevation element of the corresponding points.
Starting with GDAL/OGR 1.8.0, if a layer is named "track_points" with wkbPoint/wkbPoint25D geometries, the tracks in the GPX file will be built from the sequence of features in that layer. This is the way of setting GPX attributes for each track point, in addition to the raw coordinates. Points belonging to the same track are identified thanks to the same value of the 'track_fid' field (and it will be broken into track segments according to the value of the 'track_seg_id' field). They must be written in sequence so that track objects are properly reconstructed. The 'track_name' field can be set on the first track point to fill the <name> element of the track. Similarly, if a layer is named "route_points" with wkbPoint/wkbPoint25D geometries, the routes in the GPX file will be built from the sequence of points with the same value of the 'route_fid' field. The 'route_name' field can be set on the first track point to fill the <name> element of the route.
The GPX writer supports the following layer creation options:
The GPX writer supports the following dataset creation options:
Waypoints, routes and tracks must be written into that order to be valid against the XML Schema.
When translating from a source dataset, it may be necessary to rename the field names from the source dataset to the expected GPX attribute names, such as <name>, <desc>, etc... This can be done with a OGR VRT dataset, or by using the "-sql" option of the ogr2ogr utility.
To avoid this, starting with GDAL 1.6.1, you can define the GPX_SHORT_NAMES configuration option to TRUE to make them be reported respectively as "trksegid" and "trksegptid", which will allow them to be unique once translated to DBF. The "route_point_id" field of route_points layer will also be renamed to "rteptid". But note that no particular processing will be done for any extension field names.
To translate the track_points layer of a GPX file to a set of shapefiles :
ogr2ogr --config GPX_SHORT_NAMES YES out input.gpx track_points
Starting with GDAL 1.6.0, you can use the OGR SQL CAST operator to convert the time field to a string :
ogr2ogr out input.gpx -sql "SELECT ele, CAST(time AS character(32)) FROM waypoints"Starting with GDAL 1.7.0, there is a more convenient way to select all fields and ask for the conversion of the ones of a given type to strings:
ogr2ogr out input.gpx -fieldTypeToString DateTime
The driver supports reading and writing to files managed by VSI Virtual File System API, which include "regular" files, as well as files in the /vsizip/ (read-write) , /vsigzip/ (read-write) , /vsicurl/ (read-only) domains.
Writing to /dev/stdout or /vsistdout/ is also supported.
ogrinfo -ro -al input.gpx
ogr2ogr -f GPX output.gpx input.gpx waypoints routes tracks
ogr2ogr -f GPX -dsco GPX_USE_EXTENSIONS=YES output.gpx inputwhich will give an output like the following one :
<?xml version="1.0"?> <gpx version="1.1" creator="GDAL 1.5dev" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ogr="http://osgeo.org/gdal" xmlns="http://www.topografix.com/GPX/1/1" xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd"> <wpt lat="1" lon="2"> <extensions> <ogr:Primary_ID>PID5</ogr:Primary_ID> <ogr:Secondary_ID>SID5</ogr:Secondary_ID> </extensions> </wpt> <wpt lat="3" lon="4"> <extensions> <ogr:Primary_ID>PID4</ogr:Primary_ID> <ogr:Secondary_ID>SID4</ogr:Secondary_ID> </extensions> </wpt> </gpx>
ogr2ogr -f GPX output.gpx input.shp -sql "SELECT field1 AS name, field2 AS desc FROM input"
This error happens when the layer to create does not expose a precise geometry type, but just a generic wkbUnknown type. This is for example the case when using ogr2ogr with a SQL request to a PostgreSQL datasource. You must then explicitly specify -nlt POINT (or LINESTRING or MULTILINESTRING).