this post was submitted on 23 Nov 2023
427 points (98.9% liked)
Technology
58303 readers
13 users here now
This is a most excellent place for technology news and articles.
Our Rules
- Follow the lemmy.world rules.
- Only tech related content.
- Be excellent to each another!
- Mod approved content bots can post up to 10 articles per day.
- Threads asking for personal tech support may be deleted.
- Politics threads may be removed.
- No memes allowed as posts, OK to post as comments.
- Only approved bots from the list below, to ask if your bot can be added please contact us.
- Check for duplicates before posting, duplicates may be removed
Approved Bots
founded 1 year ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
The GPS chips have internal limits on how fast they think they can move. If they determine that they are moving faster than 300m/s they will stop outputting any results for a period of time. This limit is, IIRC, put in at the silicon level, so only military chips can bypass it.
If you try to use mapping apps on a plane you sometimes run into this issue.
It is trivial to make your GPS receiver firmware ignore these limits. There are even open-source receivers (SwiftNav piksi, for example). Modifying a binary is much harder, but not impossible for a motivated state like Iran or Russia. It's best to think of the COCOM limits as suggestions.
But even the fastest airliners at the moment (A330 neo) moves slower than 300m/s. Wikipedia claims that COCOM limits are even higher so I don't think that they are the reason for the inaccurate tracking on planes.
There's also a height limit
Turns out it's 1000 knots (~600m/s), or 18,000 feet. So it's the altitude in this case. But a slow-moving drone at <18,000ft is fine.
Maybe a misapplication then. I've run into it with model rocketry before (for good reason)
Oh, neat. I was not aware of that. I have seen that before but thought it was due to the phone not being able to lock on to the signal from inside a big metal tube.