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For many users, Altitude gained or lost is as important as distance traveled, and Memory-Map for All has advanced tools to collect and record the altitude on your device.
GPS altitude readings tend to be very noisy, and are much less accurate than the horizontal position. A typical mobile device might have random errors of 10 ft horizontally, and up to 50 ft vertically.
Most mobile phones have a built-in barometer, that gives highly accurate differences in altitude, but it can be affected by the weather.
If you go to the Main menu, Settings, Altitude Settings you can select from 4 modes.
•No Altitude. The barometer is turned off and no altitude data is recorded in the tracklog. This also disables various height-based features, and is appropriate if you are only interested in 2D navigation.
•Barometer only. Records changes in altitude based only on the barometer. You have to set the starting altitude at a known position.
•GPS Only. The barometer is turned off and altitude is taken from the GPS only. The data is smoothed so rapid changes in altitude are filtered out, but you should expect to see occasional step-changes.
•Blend GPS + Baro. Records a blend of smoothed GPS with accurate changes from the barometer.
•Terrain Elevation. Your altitude is assumed to be at the mapped height of the ground (ignores GPS height and barometer)
Note. Barometer is available on iOS and some Android devices only.
With any of the altitude modes (except "Terrain"), you can adjust the current altitude reading. This sets an offset which is added or subtracted to the sensor readings, so that the result agrees with the vertical datum of your topo map.
You can adjust the smoothing time constants that the app uses for filtering both the GPS Altitude and Barometric altitude. Depending on the noise characteristics and smoothing built-in to your device, you may need to adjust these to get good results on your device. If you find the Ascent and Descent are reading too high, you may try increasing the smoothing time constants.
In "Blend" mode, we recommend using a long smoothing time for GPS, up to say 60 minutes. This will totally smooth out any weird jumps in GPS altitude, while providing a stable reference for the Barometric hight and correcting for slow changes in the weather.
If you are using an external GPS make sure it sends the GGA sentence if you want altitude data
Recommendations for best results:
•If you are only interested in changes in height over a few hours, use Barometric-only mode
•Set the Altitude correction before you start recording a track. If you adjust it during a recording, the track will have a jump in altitude.
•If using GPS or Blend mode, allow the GPS to run for several minutes before setting the altitude.
•For the iPhone, we recommend a 20 minute GPS smoothing and zero barometer smoothing. Settings for Android devices will vary widely, but 20 minute GPS smoothing and 60 seconds barometer smoothing is a good place to start.
•Not all devices are able to record a meaningful altitude profile due to GPS and barometer sensor performance. In our testing we found the iPhone 12 mini produced the most consistent readings, while some android phones were not able to give meaningful ascent/decent data with either GPS or barometer.
•The terrain setting will give the same altitude profile as you would see on a planned route. Note, this method also over-estimates ascent/decent when you are traversing a steep hillside or walking along a sharp ridge, due to quantization noise.
Next: Route Settings
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