Manipulating GPS Tracks

Download data.  Note where you save the downloads.


Open map data to create a base map.  You have two options, and can put the other data atop either of the maps.

Database button on map toolbar.  Do this from the map toolbar, so it overlays your base map.  The other DB button only allows data analysis, not map functionality.

Basic direction for the MICRODEM GIS program


Edits to the database.  Some of these can be temperamental; if they do not appear to work, repeat the operation which generally succeeds the second time.  You must turn on edits first with the checkbox.


Map Displays.  Some will not be appropriate for all data sets.

  • Vector data: on PLOT button of table display window.  Shows the speed with a vector, scaled by the speed; you can control how big you want the vectors to be with the Line Multiple.  You can also plot every nth reading, to control the clarity of the display, with the Thin option.  Color can be another variable, in this case time, which shows how the GPS moved over time.

 

 

Database Filters can help you see patterns.

All readings.
Filter to show just the speeds over 10 km/hr.  Single isolated values might be bad data, but where a lot of data is fast, the data is probably good.  After a filter any subsequent operation uses just the selected subset of the data.

Graphs from Stats button on table display window

  • 2D graph, and either  plot points, or lines connecting the point.
  • 2D graph, two series

Histogram

Rose Diagram (circular histogram)

This examples show anomalies that the four principle compass directions are over represented.

For the database, use KML: export for Google earth  choice on the Report menu of the database table form

Display map in Google Earth:  On map, right click on map, then Export either
  • Quick map to Google Earth:
  • Deliberate map to Google Earth:

This image has turned off the map layer, but left on the pushpins for each GPS reading.  Zoom in and click on a pushpin, to see the database record.


Last revision 1/31/2016