Ignore lat/long/altitude of 0,0,0, or invalid fixes

[tris]

There are a few invalid track points near the beginning of this recording (which render a line all the way across the planet):
https://flyxc.app/?id=5075417361285120

IGC attached below -- focus on these lines:

B1810463645902N11905883WA0135101418
B1810473645902N11905883WA0135101418
B1810530000000N00000000EV0135100000
B1810540000000N00000000EV0135100000
B1810550000000N00000000EV0135100000
B1810570000000N00000000EV0135100000
B1811020000000N00000000EV0135100000
B1811033645901N11905884WA0135101417
B1811043645901N11905884WA0135101417

According to the IGC spec, "fix validity" is a bit overloaded -- "V" can mean either that the fix is missing altitude, or that GPS is lost completely. ("Pressure altitude data must continue to be recorded", which I suppose is why these lines are in here at all.). So, I guess flyXC should look for lat/long of 0 and discard those useless points.

2025-04-20-XNA-28E8BCE2E385AAD296C1CD2EB6FCC2A3-01.igc.txt

[vicb]

Salut Tristan,

How frequently does this happen?

I would prefer not have to filter IGC files (to avoid false positive).

Notes:

flyXC uses igc-parser which surfaces valid

If you want to submit a PR, the code is at https://github.com/vicb/flyXC/blob/master/apps/fxc-server/src/app/parser/igc.ts
Would be nice to add a test, see gpx.test.ts in the same folder as a starting point

[deviljf]

I have the same problem. There are some strange coordinate entries that don't match the South African location:
The anomalous line:
B1215340000000N00000000EV0066000000
This line shows coordinates of 00°00'000"N 00°00'000"E - which is the intersection of the Prime Meridian and Equator in the Gulf of Guinea off the coast of West Africa (sometimes called "Null Island"). This is clearly a GPS error or invalid data point.
Normal coordinates in your file:

Most entries show: 3343142S01904283E = 33.43°S, 19.04°E (Cape Town area)
The anomaly shows: 0000000N00000000E = 0.00°N, 0.00°E (Gulf of Guinea)

This type of GPS error is common in IGC files when:

GPS signal is temporarily lost
The device experiences a software glitch
There's interference with satellite reception
The logger records a default/null position

The flight analysis software should typically filter out or interpolate over these obviously erroneous coordinates. The rest of your track data consistently shows the flight happening around Cape Town, South Africa, not Europe or anywhere near the equator.
This is a classic example of why GPS track cleaning and validation is important in flight analysis

What you see in FlyXC is a line drawn across from my flight track to the equator. It happened a few times using Seeyou Naviter on the Iphone.