GPS Exchange format, a generic format used to extract data recorded by GPS devices.  GPX files typically contain Latitude/Longitude coordinates for points and lines, often with elevations and at times with detailed information on the operation of the GPS device at the time the data was acquired.  


The sample GPX file imported in this topic is similar to that used in the Manifold 9 - A Walk in the Rain Forest video.



To import from GPX format:


  1. Choose File-Import from the main menu.

  2. In the Import dialog browse to the folder containing data of interest.

  3. Double-click the file ending in .gpx for the data of interest.

  4. Tables and drawings will be created.



The Map file above shows the other drawings as layers.   Some drawings might be empty:  For example, if the GPS has no routes or waypoints those drawings might not contain any data.   


We can double-click on either the map or the drawings to view them.   For a more interesting display, we first create a new data source using a Bing street maps imageserver as shown in the Example: An Imageserver Tutorial topic.   We then create a map and drag and drop the Bing layer into the map, and then we drag and drop the parkland TrackPoints Drawing into the map.   We also add a Bing satellite layer.



The track points drawing appears using the correct projection, in the right location.  We have colored the dots in the track points using Style to provide a bright green color.    From the location of the town of Mackay, right away we can see the GPS information was collected in Australia.



Zooming in and switching to the satellite view we can see the points that were collected by the GPS.



Opening the parkland TrackPoints table we can see the data associated with each record.  Most GPX files import with NULLs in most of the data fields, since very few people will bother to export the many parameters the GPS might collect.     Note that the table has a gray background, indicating it is not editable nor selectable.  That is because the table does not have an index.


Using the procedure given in the Add an Index to a Table topic, we take a moment to add an mfd_id key field and corresponding index.



That makes the table selectable, and also allows us to make selections in the drawing.



For example, if we want to get an idea of the elevations near the beach in the illustration above, we can select those points near the beach.



In the table we use a filter to show only selected records.



Extensions - Manifold's GPX dataport reads GPX 1.1, harvesting fields in that specification's schema.   GPX is an XML format and allows custom extensions, which can hold any XML content.   Manifold ignores custom extensions.  To import a GPX containing custom extensions, use the GDAL / OGR dataport.


Extracting latitude and longitude - The GPX dataport creates a geometry field, called Geom, to capture the position of each point, as seen in the illustration below.  To create fields that provide explicit latitude and longitude values, as might be required by some other applications, use the procedure shown in the Example: Create a Geocoded Table from a Drawing  topic.



See Also











Add an Index to a Table


Example: Spectacular Images and Data from Web Servers


Example: An Imageserver Tutorial


Example: Create a Geocoded Table from a Drawing



Manifold 9 - A Walk in the Rain Forest