Using GPS data for Trail Simulation

In order to accurately simulate trail users, usage data must be acquired. Typically this kind of data is collected by paper surveys, on trail interviews or by hand (physically counting users). We propose a more automated method of data collection using user submitted GPS tracks. As GPS device use among recreators increases the data being produced will only increase.

There are several advantages of using GPS data. The first is in the GPS data itself; accurate representations of trails are possible. Using TopoFusion's network algorithm, multiple tracks can be combined and averaged together to automatically form a trail network suitable for running simulations on. This step alone can save hours of effort in obtaining trail data (probably from different sources), cleaning it up and combining it into a usable form.

Second, GPS tracks contain time information. This means that speed of travel, duration of stay and other temporal statistics can be extracted. Without this information simulations are left only with Digital Elevation Model (DEM) data at rough 30m resolution for estimating travel time based on slope and mode of travel. The DEM data is both inaccurate (for interpolation) and does not account for roughness and other trail conditions that greatly effect travel speed. It is our view that using GPS time data will greatly improve the modeling of trail users.

Third, given a sufficiently large number of GPS tracks, various usage statistics can be determined. Examples include the frequency with which trails are traveled on, time of day and seasonal use. Typical trips can be extracted and programmed directly into the recreational agent's logic.

Fourth, the process of creating trail networks with speed and usage statistics can be almost completely automated. This can save hours of entering data, annotating networks and setting up agent statistics.

Fifth, this approach allows the public to actively participate. Often trail users inquire how they can help and "give back" to the parks that they love. Contributing GPS tracks and thereby helping land managers make the best, most accurate decisions is one way they can help.

There are also a number of disadvantages to this approach. Foremost, GPS data is not yet widely available. We are curious as to what percentage of recreators own and use GPS devices. We have yet to find any studies done on this subject. We only know that GPS use is becoming increasingly popular. If our GPS-oriented trail simulation is not feasible now, we anticipate that it will be.

We are also interested in maintaining large online GPS trail databases. See Discussion of Public Participation Online Trail Databases for our view on the problems associated with trail databases and how we are solving using the network algorithm in TopoFusion. If such databases existed they would provide incentive to trail users to submit data (since they would be able to access other users' data). The submitted tracks could then also be used for simulation (and simple statistical) purposes.

We have embarked on our TMP Project both as a prototype for our software and to "test the waters" of asking the public for GPS tracks.

For questions & comments, email:

sim@topofusion.com