If you don't supply a distance unit (feet, miles, etc.), the threshold given is assumed to be in meters.
The newer "trackpoint distance threshold" filter examines each point in a track, in order, and discards every trackpoint that is not at least X distance from the last non-discarded point you get to choose the value of X. Obviously, we need another approach to cleaning up track data automatically. If we set the maximum number of points to 6, the jaggedness is preserved, because the simplification filter thought that all those sharp angles were important! This is not an ideal result. (Of course, it's also possible that this jagged line reflects reality, but let's assume for now that it's just the result of unwanted artifacts in the raw data.) As you can see, something weird is happening between point #3 and point #8 if this was a GPS track, it's likely that the person recording the track stopped for a minute, and the GPS signal "wandered around" while he or she stood still. Here's another hypothetical track, this time with 11 points. (For example, Garmin's older GPSMap units only allow 500 points per track.) But now let's look at an example where the "preserve the shape of the track" method doesn't work as well. points" setting works well on relatively clean data, and it's very useful if you need to reduce the number of points in a track because your GPS device has a specific limit. If we set the maximum number of points to 6, four of the points on the "straightaway" sections of the track are removed, leaving us with a modified track that looks very much like the original: For example, here's a track with 10 points: points per track" option, which has been available since 2006, reduces the number of points in a track by passing the track through GPSBabel and asking GPSBabel's simplify filter to remove the most redundant points, based on how much those removals will affect the overall shape of the track (in technical terms, it measures "cross-track error").
They both reduce the number of trackpoints (while preserving time stamps and other information), but in very different ways. points per track ( trk_simplify) and trackpoint distance threshold ( trk_distance_threshold). There are two options in GPS Visualizer's mapping and file conversion input forms that allow you to "simplify" your tracks: Max. « GPS Visualizer Tutorials Tutorial: Smoothing & Simplifying Tracks No ads? No problem! You can support GPS Visualizer by making a donation with PayPal instead.
0 kommentar(er)
