Distance calculation algorithm
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Does the distance calculation algorithm used by mapy.com account for elevation, or is it just flat projection measurement as I would do on a paper map? I am getting quite different distance information when I compare the planned route and a recorded GPS track. It is like 12km planned and 16km in reality with no major glitches in the GPS recording. The terrain was not flat, but not alpine either.
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No mapping websites (including those using the Mercator projection, such as mapy.com) take the elevation profile into account when calculating route distance.
The distance is always measured “in 2D” — along the Earth’s surface (sphere/ellipsoid), plus any accumulated ascent/descent shown separately.The difference between the planned route and the recorded GPS track is usually caused by GPS inaccuracy and lateral drift (“track jitter”), not by elevation changes.
The planned route length is generally very accurate, while the distance measured from a recorded track can easily become inflated due to small side deviations in the recording. -
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@Jan-Buriánek Thanks for the info. I wonder why the elevation is not accounted for when the information is there. I believe it can be some difference when the terrain is hilly, not to mention really mountainous terrain.
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Hi, I have processed the issue of elevation gain not being taken into account when measuring distance into a web page here.
I performed the analyses on my website gpxmapy.cz, where I added the possibility to display distance values with elevation taken into account for comparison purposes. It turned out that differences greater than 1% are only possible in high mountain terrain.
The page also briefly explains the principle of distance calculation on a route — the difference between a planned route and a recorded track is always caused by inaccuracies in the recording.
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