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--- en:help:1.4:landmarks:statistics [2014/11/02 19:19] – [Gain and loss] alpinequest
+++ en:help:1.4:landmarks:statistics [Unknown date] (current) – removed - external edit (Unknown date) 127.0.0.1
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-====== Tracks statistics ======
-===== Gain and loss =====
-The gain is an important value that helps to appreciate the overall profile of a track. A small gain means that the track is mostly flat, a high gain means you'll have to climb a lot.
-Strictly speaking,
-  * The **gain** is the sum of all **positive** altitude differences along the track;
-  * The **loss** is the sum of all **negative** altitude differences along the track.
-In order to compute these values, it's important to define more precisely what means "along the track".
-A first definition would be to take into account **the altitude differences between mountain passes and summits**. If you start a hike at +150m, climb to a summit at +500m, then go back to your start location at +150m, your gain will be 350m. In practice, trails usually don't go straight forward to the summit, but will go uphill for some time, then downhill a little bit, then uphill again, etc. This first definition doesn't take all these small changes into account, and will then lead to an **under-estimated gain**.
-Another definition would then be to take into account **the altitude differences between all the locations that make the track**. Now imagine a track recorded with a GPS along the sea. The GPS, having an imperfect accuracy, will record altitudes of [+1m, +2m, 0m, +1m, -1m, +2m, ...]. With this small segment of 6 locations, we have gain of +5m. With a track of 1000 locations, it would lead to a gain of more than +800m which is a very **over-estimated gain**, since the track is along a flat shoreline and should have a no gain.