JOSM/Plugins/ElevationProfile
Contents |
Introduction
The JOSM Plugin ElevationProfile displays the profile of a GPS trace's elevation measurements. It also shows the minimum and maximum elevation in a separate layer.
| Icon | JOSM Version | Plugin Version | Maintained By | Date | Maturity |
|---|---|---|---|---|---|
 |
4487 | 28150 | OliverW | March, 26th, 2012 | Beta |
Revision History
| Version | Changes |
|---|---|
| 28150 | Fixes Ticket #7549 |
| 27286 | Removed en_GB from list of imperial countries |
| 26946 | Fixes Ticket #6991 |
| 24034 | Fixes Ticket #5598 |
| 23977 | Fixes Ticket #5558 |
Installation
- Open JOSM and select from menu Edit > Preferences, then choose the tab Plugins.
- Check ElevationProfile in the list (see figure 1), then press Update. JOSM should then download and install the plugin.
- Finally restart JOSM, that's it.
Usage
Quite simple, really. The elevation mode is (de)activated via the (
) button, you should find it on the left toolbar. This mode is enabled by default after installation. If you do not need it, simply press the button and the elevation profile window disappears.
Besides the panel on the right side you see also an additional layer named Elevation profile. This layer shows you the
- Minimum elevation (a blue triangle directing to the bottom) and the elevation in meters
- Maximum elevation (a blue triangle directing to the top) and the elevation in meters
- Start and end of the track (large green/red sphere).
- The other way points are shown in 'green' for elevation gain or 'red' for elevation losses.
- Labels with green triangle indicate a crossing of an elevation level in upward direction, red in downward.
- Cursor: Move the mouse over the profile and see the corresponding point in the map view as a large yellow sphere, labeled with the corresponding time and elevation.
See figure (3) for an example.
Hints
- The elevation panel shows only a subset of the waypoints, depending on the panel size.
- An elevation label is hidden, if it overlaps with another label. Thus, the range of elevation labels may look inconsistent (e. g. an "400m downhill" is followed by a "300m uphill". Zoom in to see missing labels.
If you have further suggestions or questions - feel free to drop me a line.
GPS Elevation Data
Many GPS devices log the elevation. Please refer to the manual or check your GPX file for tags named "ele".
However, there is a diffference between the topo height (measured with GPS) and the geoid height, Witold Fraczek wrote an excellent article on this issue. So the new version offers to correct the elevation data with geoid values. Please note, that the internal geoid table is simplified (the orginal data set by NASA/EGM is about 13 MBytes large), since a Java class constant table is limited to 64K. The consequence is that the simplified geoid value may differ up to 5m due to averaging effects. Another solution for this may be to use a lightweight DB like [SQLite].
GPS Visualizer
If your GPS device does not support elevation or you had poor signal quality during logging, you may augment your recorded GPS traces with elevation data using the GPS Visualizer.
NASA Elevation Data
An alternative is to get the SRTM (Shuttle Radar Topography Mission) raw elevation data. They come as raw files where each tile coveres 1 degree in NS/EW and consists of 1201 entries in each direction. The height (elevation about sea level) is represented as 2 byte signed integer, so that each file is 1201 x 1201 x 2 = 2.884.802 Bytes. This resolution corresponds to a square of ca. 90m x 90m. Data voids are indicated by a value of -32767.
The data of the USA is much more accurate (25.934.402 Bytes, grid size 30m x 30m).
For the curious: Mission Statement.
Further Work
The current state may be ok for a first shot, but there is still much room for improvement. Especially I would like to improve the data quality. This may be accomplished in two different ways - Data reduction/smoothing. - Augment/correct the GPS elevation data with the NASA data.
Known Bugs and Workarounds
- The elevation profile does not update when selecting another GPX layer. This is because JOSM does not notify listeners when the layer selection changes.
Workaround: Select the desired layer and change its visibility.
- The current version is only able to show a downsampled overview. Further levels of detail are considered in the model, but are not accessible via the UI yet. Please be patient.
Feedback
Please report bugs or annoyances to me by either
- send me a mail OR
- create a new TRAC ticket
