Nowadays, we all know the heights of all the mountains but have you ever wondered how they're measured? Or how possibly you could measure them? Or how were they measured in the past?
On early maps, there were no heights. Maps would show the mountains but with no heights, giving no clue as to how long it would take you to climb the mountain. It could be ten minutes or seven hours.
And how are the heights measured nowadays?
Here's one example for you. Here's how Britain's national maping agency - Ordnance Survey - measures the heights of the mountains.
Ordnance Survey use a method called photogrammetry. What they do is they fly over an area and take lots of overlapping photographs (high-resolution). Then, from these images, a 3D model is being created. This method allows for accuracy of about 10 centimetres. Ordnance Survey use two planes for their mapping process - two Cessna 404 planes - which have names: G-TASK and G-FIFA. Every year, between March and November, they take about 50,000 photographs.
There has been a lot of progress in measuring heights using photogrammetry. The ones done a few decades ago were much less precise, with accuracy of about 1-2 metres.
And here's something interesting for you:
Highest Mountains in the World
Highest from sea-level:
Mount Everest - 8848m
Highest from bottom to top:
Mauna Kea -10000m
Furtherst from the Earth centre:
Chimborazo -6,384.4 km from the Earth's centre (2,163 m further than Everest)