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muccc / iridium-toolkit

A set of tools to parse Iridium frames
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livemap.py misses some satellites with q.alt test #115

Closed SittingDuc closed 7 months ago

SittingDuc commented 7 months ago

At or about line 96 of livemap.py is a check for if a data point is on the ground or in the sky. Sky is defined as >700 and <800. Is there any particular reason 800 was chosen?

https://github.com/muccc/iridium-toolkit/blob/0705e50c905c6801b827aafa5d9abebeba0774f0/iridiumtk/reassembler/livemap.py#L96

I am asking because I see no satellite numbers on my blobmap. And when I added a printf to the function, I am getting q.alt of 808 or 819, which clearly implies iridium satellites fly a little bit higher over my house (and probably upside down too: context being I am situated in New Zealand)

For my local clone, I have lifted the bounds check to 900 and now I see satellite tracks and beams and everything is good; but before I start down the path of fork and PR, I want to check if there was a reason for the 800 value.

Sec42 commented 7 months ago

Hi,

I was assuming that since the orbits of the iridium satellites are nearly circular their altitude would be about the same everywhere. I did some quick checks for NZ, and indeed their altitude there is higher. I guess the earth's lack of roundness is enough to throw you out of the quick sanity check I put there.

I'll amended the upper limit to 850 for now.

SittingDuc commented 7 months ago

Oblate spheroid, huh. Thabks for the fix :)