eli5 How did people draw maps before satellites?
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Carefully and laboriously. This is the task of surveyors; to take careful distance, bearing and elevation measurements between fixed points and so build up an overall picture. Lots of hilltops in the UK for example have triangulation “trig” points on the top which were used by Ordnance Survey to site measuring instruments and so get accurate bearings to lots of visible landmarks (other hilltops, church spires etc). If you can see several of those landmarks from another trig point then you can draw two bearings on a map and where the lines cross is where the landmark is. Continue this process across a large area and hey presto you have a map!
The height of for example Everest was measured in this way: they started at the sea and measured from point to point all the way up until they could see the top, which is many hundreds of miles from the sea.
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