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GPS navigator on a space station

NeoFatalis

By NeoFatalis
in Science & Spaceflight

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NeoFatalis

NeoFatalis

Posted
Posted

For example you managed to get a normal GPS navigator or a smartphone with some kind of navigation program like google maps on a space station , will it be able to catch GPS signals? And if it will what do you think it would show?

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Superfluous J

Superfluous J

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What @magnemoe said, with the additional note that gps isn't a 2d thing on the surface of a sphere. They pinpoint you in 3d space and then tell you where you are on a 2d map, ignoring (but frequently making available) your height.

Also note that modern phone GPSes get a lot of help from things you won't have in space, namely cell towers and Google's map of wifi hotspots. Yes, being near a Starbucks frequently means you'll get better location pinpointing.

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Elthy

Elthy

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Isnt the limitation of GPS in altitude/speed only implemented in software? Should be "easy" to circumvent on Android phones. Sadly everything i find about GPS limitations on Android is about Pokemon Go hacks...

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magnemoe

magnemoe

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48 minutes ago, Nibb31 said:

Current LEO spacecraft like Dragon or the latest Soyuz already use GPS for navigation, so yes it is possible.

Makes lots of sense, one of the issues in space is knowing your position. Without GPS or similar systems you have to triangulate it from ground stations then calculate your position then out of range, now if you do an correction burn you get your new speed after knowing your acceleration over time but its always errors so you need an new triangulation if you do multiple orbits. GPS will speed up this, by giving new positions and then speed after burns speeding things up. 

Issue with GPS at high speed and attitude is that you need an military version its not something you can unlock on a phone. 

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wizzlebippi

wizzlebippi

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33 minutes ago, NeoFatalis said:

So basically if you open a GPS app in space your phone will get a brain fart:mellow:

It doesn't even need to be in space.  Next time you fly on an airliner, have a navigation app open.  Your phone will drop GPS shortly into the takeoff roll because it senses excessive acceleration.  For entertainment, if you get the chance to fly on something smaller and slower like a skyhawk, open a navigation app and watch it try to figure out where you are. 

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Elthy

Elthy

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How exatcly is this lock archived? If understood GPS correctly it recieves a combination of time/location from each satellite, which get combined with some maths for the location. This math should work no matter how fast the reciever is moving, i can only imagine its software to output nothing if it notices the speed/altitude is to high...

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YNM

YNM

Posted
Posted (edited)
10 hours ago, Elthy said:

How exatcly is this lock archived? If understood GPS correctly it recieves a combination of time/location from each satellite, which get combined with some maths for the location. This math should work no matter how fast the reciever is moving, i can only imagine its software to output nothing if it notices the speed/altitude is to high...

Yes. It actually knows where you are, even while "not working" in the discussed scenario.

EDIT : Read GoSlash27 reply, seems to be more than just "not showing you the results".

Edited by YNM
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Superfluous J

Superfluous J

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4 hours ago, YNM said:

Yes. It actually knows where you are, even while "not working" in the discussed scenario.

Like how my car won't lock with the engine running. There's no technical reason why it can't, but dumb people (or in GPS's case the turrists) have caused the manufacturer to limit my options.

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GoSlash27

GoSlash27

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11 hours ago, Elthy said:

Isnt the limitation of GPS in altitude/speed only implemented in software? Should be "easy" to circumvent on Android phones. Sadly everything i find about GPS limitations on Android is about Pokemon Go hacks...

 Sadly, no. GPS chipsets for commercial use have "export restriction" built into them. It's not something that can be bypassed or hacked.

If it detects accelerations, velocities, or altitudes that exceed the limits, it will refuse to track for 15 minutes.

This is to keep someone from using a commercial receiver to guide a missile.

Best,
-Slashy

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GoSlash27

GoSlash27

Posted
Posted (edited)
6 hours ago, Elthy said:

How exatcly is this lock archived? If understood GPS correctly it recieves a combination of time/location from each satellite, which get combined with some maths for the location. This math should work no matter how fast the reciever is moving, i can only imagine its software to output nothing if it notices the speed/altitude is to high...

It varies by manufacturer, but here's what happens in the "Aries" chipset I worked with early in my career:

If it detects a condition outside of COCOM limits, it immediately disables output, replacing it with an "export restriction mode" flag and 15 minute countdown.

It then dumps the scratchpad ram, ephemeris data, and channel keys. Without this "almanac" it has no idea where it is or where the satellites are.

It won't attempt to find a satellite after that until the countdown timer elapses.

Furthermore, the chip is programmed serially using JTAG and the ports are severed using a fusible link. There's no way to reprogram the part or look at the program that went into it.

 

That was over 15 years ago, so things might've changed.

Best,
-Slashy

Edited by GoSlash27
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magnemoe

magnemoe

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11 hours ago, wizzlebippi said:

It doesn't even need to be in space.  Next time you fly on an airliner, have a navigation app open.  Your phone will drop GPS shortly into the takeoff roll because it senses excessive acceleration.  For entertainment, if you get the chance to fly on something smaller and slower like a skyhawk, open a navigation app and watch it try to figure out where you are. 

Weird, acceleration during takeoff is not much worse than an sports car or motorcycle, yes after some minutes you are going fast and you will also go high so this causes the lock down. The climb rate might also cause this, 

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YNM

YNM

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3 hours ago, GoSlash27 said:

It varies by manufacturer, but here's what happens in the "Aries" chipset I worked with early in my career:

If it detects a condition outside of COCOM limits, it immediately disables output, replacing it with an "export restriction mode" flag and 15 minute countdown.

It then dumps the scratchpad ram, ephemeris data, and channel keys. Without this "almanac" it has no idea where it is or where the satellites are.

It won't attempt to find a satellite after that until the countdown timer elapses.

Furthermore, the chip is programmed serially using JTAG and the ports are severed using a fusible link. There's no way to reprogram the part or look at the program that went into it.

 

That was over 15 years ago, so things might've changed.

Best,
-Slashy

Guess they won't change it. But some people have attached JTAG ports to their phones just to get it out of "brick", so...

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linuxgurugamer

linuxgurugamer

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48 minutes ago, magnemoe said:

Weird, acceleration during takeoff is not much worse than an sports car or motorcycle, yes after some minutes you are going fast and you will also go high so this causes the lock down. The climb rate might also cause this, 

The speed limitation must be higher than 400mph, cause I had my Garmin on a plane, and once it got the signal, it showed me our location in real time.  Speed was somewhere between 350 and 450 mph.

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GoSlash27

GoSlash27

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4 minutes ago, YNM said:

Guess they won't change it. But some people have attached JTAG ports to their phones just to get it out of "brick", so...

I don't know of any way to restore a JTAG programming port once it's been burned, but even assuming that it's possible... it'd be silly to go to all that trouble just to reprogram a commercial chipset in situ. Much simpler to put your "pirate GPS" program into a blank FPGA and be done with it.

Best,
-Slashy

5 minutes ago, linuxgurugamer said:

The speed limitation must be higher than 400mph, cause I had my Garmin on a plane, and once it got the signal, it showed me our location in real time.  Speed was somewhere between 350 and 450 mph.

The official limits are 1,200 MPH and 59,000' altitude. http://ravtrack.com/GPStracking/cocom-gps-tracking-limits/469/

Best,
-Slashy

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