Terrain - Above Ground Level Information
Ground Level Information
The XC Vario supports ground level information with respect to the underlying ground surface. Besides providing information known as height above ground level (AGL), ground level information is also used to indicate a rough orientation for the vertical distance to airspaces.
ground level information of 526m for lake bohinj in slovenia
The ground level information used in our phone varios is based on high resolution 1° x 1° terrain tiles, as opposed to the widely used low resolution tiles in many commercial varios that one can buy. Each 1° x 1° terrain tile provides in total 12.967.201 heights or data points providing elevations with a resolution of roughly 20m x 30m within each tile. Tiles are available for almost all regions of the earth.
For most european countries extremely detailed lidar data exists and is partially used. Even remote places like Iceland are covered.
Importing Terrain Tiles
Importing Terrain Tiles is accomplished by simply clicking on the required region to download elevation data. Tiles for many regions of the earth are already highlighted to make the process of downloading for paragliding sites and areas more comfortable. However, download is not restricted to these regions. You can click anywhere you need to create and highlight a new terrain tile and click again to download. Only few if any paragliding pilot at all gets to fly all regions or sites. So downloading only what you need wont take more memory on your phone vario as really needed.
click on a premarked terrain tile or anywhere else to download ground level information
Terrain Views and Above Ground Level during flight
While paragliding the information on ground level heights is being used and visualized in different features within the variometer app.
1417m above ground level with vertical terrain view airspace on top visualized
Above Ground Level Information
One feature used in the XC Vario is the AGL in m field that indicates the expected difference in meter between your flight altitude and the ground elevation. This is the expected difference and cannot ever be 100% accurate due to two reasons.
Reason 1: the information processed from the terrain tiles is most of the times very good but not perfect due to failed or empty readings, abrupt changes in terrain and or other sources of error that are inherent to digital elevation models (DEM) and simply happen when you try to scan the earth from an altitude of 233 kilometers above the earth to generate a digital elevation model.
Reason 2: the altitude you are flying at and that is used to calculate the above ground level information is obtained from GNSS NMEA readings of the phone which varies depending on the phone, chipset and the quality of the current GNSS fix. Advanced chipsets may use Dual Rate technology like the Pixel 6 or comparable others may not and be less precise and accurate. In any way AGL values should just be seen as a rough estimation.
Vertical Terrain View
Another feature utilized by the vario is the terrain view that appears once your flying approximately straight. In this case the terrain ahead of you is visualized together with your current flight path with respect to your expected altitude at a certain distance. The terrain view looks 5000 meters ahead and 1000m behind you.
Vertical Distance to Airspaces
Last but not least the above ground level information is to calculate the distances to airspaces around you and which is only visualized if you are below the vertical threshold set in the settings.