Why are poles data missing from most topographic resources ? Data from 60⁰ to 90⁰ lat frequently missing from topographic GIS data. Example with SRTM4.1:
Common sense or deduction lead me to think that either:
Orbits: the orbit does not go to poles. Which is absurd for a topographic mission.
Data : the data on poles is messed up. But come on, in 2010's, space agencies computer scientists are not able to clean this up ?
I asked myself this for years. Yet, I have no real, solid answer up to now.
Just for fun, if the there are relevant GIS resources for these 2 areas, please share.
SRTM (Shuttle Radar Topography Mission) was a shuttle mission, no satellite involved. But essentially the satellites do not cross the poles.
In a geosynchronous orbit, which most imaging satellites are in, you get a pattern like:
This is great because it means that the orbit can be timed and most parts of the Earth get covered at around noon, getting good lighting and few shadows. But essentially it is revolving around the earth in a way that the poles are never flown over.
Side effect stays, you may have missing information at poles, example with GDEM which covers 83⁰N-83⁰S :
But as we see, polar areas present more artifacts. To avoid such corrupt data, the easy solution seems to cut out poles, and 60⁰N-60⁰S
There is no SRTM data of the pole regions because
the shuttle flight did not cover that area and
the nature of the recording makes it difficult to gather data from ice areas (same as some mountain regions)