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Locus Download Elevation

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<div>Please do not confuse with current altitude that is obtained from GPS data together with values from the barometric pressure meter in your device (if applicable), see more >>. Current altitude values are also used for calculating elevation gain in recorded tracks.</div><div></div><div></div><div>LoMaps and other offline maps from our map partners offered in Locus Store in packages cover the whole World. Each map package contains elevation data that can be downloaded separately for free:</div><div></div><div></div><div></div><div></div><div></div><div>locus download elevation</div><div></div><div>Download File &#9658;&#9658;&#9658;&#9658;&#9658; https://t.co/ef2fS99U2B</div><div></div><div></div><div></div><div></div><div></div><div></div><div>Web services usually read only trackpoint coordinates during GPX import and render them above their own 3D model of terrain. Then they calculate the resulting elevation profile from the model. However, each such model is generalized (simplified) reflection of reality and therefore the elevation gain calculated from it may differ a lot from the original.</div><div></div><div></div><div>During the track recording Locus adds every centimeter of the elevation gain between individual trackpoints that may be placed just meters from each other and also raw altitude data from the GPS chip that may contain significant deviations. Due to saving the battery the data are optimized only after the record is finished and saved.</div><div></div><div></div><div>Quite a while ago, something changed and the elevation/distance graphs of my recorded tracks became much more jagged and erratic. Previously, these same routes had been fairly smooth and the total elevation gain/loss had been realistic. After the change, however, the gain numbers skyrocketed to 3x or more for a known route.</div><div></div><div></div><div>I won't rule out damage to my phone, but I wonder if there is some sensitivity setting within Locus that was changed. Which of the recording profile parameters would have the greatest influence on the elevation gain recording? Distance/time intervals or GPS accuracy?</div><div></div><div></div><div>Hi Jef,</div><div></div><div>Locus Map processes elevation gain from the data it receives from your phone GPS. If the data are incorrect or contain huge deviations, then the resulting elevation gain is also incorrect. Locus Map, however, offers a few methods on how to limit these deviations. Open Locus settings > GPS&sensors:</div><div></div><div></div><div>On planned routes is, of course, applied only SRTM source for elevation, but no filter. Elevation from HGT files is already interpolated from more values around a required place, so there definitely is no filtering needed. Huge difference you write about after planning by BRouter is really interesting. May you send me a GPX of such planned track? I would like to look at it.</div><div></div><div></div><div>thanks for a track. As I wrote, on planned routes is not applied any filtering. It is because every computed elevation value is interpolated by bicubic interpolation from 16 points around. So we may expect, that such value is already quite filtered. Anyway as I see, elevations for your route are jumping quite a lot as you wrote.</div><div></div><div></div><div></div><div></div><div></div><div></div><div>like Andrea, I also noticed that elevation filtering for planned routes is a little off. When I plan routes in Locus with Brouter the shown elevation data is (most of the time) several times higher than with other route planning apps (like OSMand or the brouter web edition). In areas I personally know, their values unfortunately seem way more plausible than Locus' values so I expect it to be the same in other areas.</div><div></div><div></div><div>I noticed that Andrea's track ist based on the Openstreetmap-streets, so it's NOT a recorded track which could suffer of horizontal jitter due to bad GPS reception. And I took the best available elevation (LIDAR) source of the region, and used them to fill the elevation of the trackpoints. The resulting elevation gains/losses calculated with Locus:</div><div></div><div></div><div>So the first important thing is: Use as exact elevtion files as possible, if available LIDAR-1". No SRTM files, no LIDAR-DTM 3" files. Even if at first sight in theory we could think "Elevation from HGT files is already interpolated from more values around a required place", and so for example a 3" and a 1"-HGT-file of the same elevation source should result in similar values, which is not true as you can see above.</div><div></div><div></div><div>Second thing: Even if have the most exact elevation files possible, it's important that the horizontal postition of a track is exact, no divergence from realitiy, no jitter due to GPS-reception. This is also quite good for this track, since it's based on OSM, hence no jitter. But even OSM roads in this region difffer some meter from aerial-images of this region. No track can be 100% exact with reality - neither if recorced by GPS nor if planned using OSM-roads. - Hence especially in alpine terrain resulting in some "virtual" altitude differences are applied.</div><div></div><div></div><div>Third: As we can see using Andrea's track, based on quite good OSM-data, using best available elevation sources it's maybe a good idea to additionally filter the resulting elevation values of the track within an app. For example I used a vertical filter of 20 m (so each alevation change of less than 20m is disregarded), and i get values -1740 m / +1046 m which quite confirms the values we estimated by eye before.</div><div></div><div></div><div>But don't forget this is just quite good because we have precise 1"-LIDAR elevation data and a good OSM-based track here. So maybe better use a filter of 20m or even more. At least for alpine roads/hikes. You still have to test how such a filter influences tracks in flater regions.</div><div></div><div></div><div>You're right menion, elevation changes of 10 meters are still changes. But you have to be careful: Are this changes "real" changes or just virtual changes due to horizontal differences of the track to reality. Example: if a road within OSM differs just horizontal 10 meters to reality - could cause the elevation be off 20, 30m in alpine terrain.</div><div></div><div></div><div>And the same systematic error is true for the fact that even if using very good 1"-elevation files, such a files covers an horiziontal area of about 20 x 30meter which also leads to the mentioned systematic vertical error.</div><div></div><div></div><div>So even if we use the best available elevation sources, quite good horizontal positioned track we get systematical vertical errors. And to remove this errors a filter is necessary. Just look at the values I got using the 1"-LIDAR files. They are still "wrong" by about 300 vertical meters without aplying an additional filter.</div><div></div><div> dca57bae1f</div>

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Locus Download Elevation Sharmaine Kass <kasssharmaine@gmail.com> - 2024-01-17 20:25 -0800

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