GPS in Iran - does it work?
 

Hello fellow travellers,
This might sound like a stupid question, but does GPS wotk in Iran? The reason I ask is because a friend of mine just travelled Iran- in november, on a bicycle - and he said his GPS didn't work. His hyppothesis was that the signal had been shut off, in connection with the (hopefully not) upcoming war in the region. I am a bit reluctant to take my friend's word about this (because he's not the sharpest tool in the shed and neither am I). Any clues on the matter are very much appreciated.
Safe travels to all!

GPS is operated by the US DoD, but they provide a standard service worldwide to any user for free. This is the GPS service you know. The accuracy of a position can be influenced by the introduction of an artificial time delay by the satellites. This is called selective availability and the position given by the GPS receiver may have an error of 100m horizontally.
I don't think the signal can be shut off over specific countries. Assume there are 3 satellites (all that is needed to get a position) just above the horizon. In this case, they may not even be straight above the country you're in. More, they are still beeming a signal in the opposite direction, covering possibly several countries at once. Think of a satellite's coverage as a giant circle sweeping across the planet as the satellite moves. Each satellite is in a near Earth orbit and as such has to move across the surface, so during the course of an hour or so, satellites appear above the horizon or dip below it, but you'll always find at least 3 above the horizon.
Thus in the example of 3 satellites just above the horizon, shutting the signal off would affect more than one country. In the case of Iran, this would affect Kuwait as well. The same satellites are used by the military, but they get an encrypted and more accurate signal.
Bottomline, I suspect GPS works in Iran, but you get a 100m error.

I think that DoD can add some "noise" to the signal... to get lower degree accuracy...

At least that's what they did during Desert Storm... I think it was around 0,5km-1km margin, which is, IMHO too much...

I bet they will do it again when US starts another agression in the region...

I'm in Iran now, and I can confirm that GPS definitely does work, with no lower sensitivity than anywhere else in the world (even with the war going on!).

James

James is right.
Here are the references for Persepolis and Masuleh courtesy of my Garmin GPS V.

Persepolis = N29 56.141 E52 53.275
Masuleh = N37 09.146 E48 59.327

Stephano

Maybe a bit late, but we have something to add anyway:

The noise on the GPS signal was removed in may 2000, so the signal is now accurate to less than 10 meters (depending on the quality of reception of course).

Some useful GPS data on Iran can be found on our website:
http://www.erwinvoogt.com/overland.html

Happy Travels!

A bit late as well, but here goes. I am not sure when your friend was in Iran, but Iraq had some GPS jamming equiptment that they got from Russia to try and jam the American weapons. It didn't work of course, but It may have been in service when you friend was there and worked on commercial units. I don't know, just guessing.

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John

I do beta-testing of GPS units for Garmin - for motorcycle applications - and they tell me that they sold a whole whack of consumer-off-the-shelf (COTS) handheld GPS units to American soldiers who went to Iraq during the most recent war, and wanted a "personal" GPS unit. So, it sounds like the COTS units do work well enough, even during a conflict.

It is correct that the US Military stopped degrading the GPS signal using selective availability (SA) back in 2000, but the only reason they made that generous gesture was because the most recent generation of satellites that they have sent up (as part of normal ongoing replacement of GPS satellites) are far more sophisticated, and the US military now has the ability to grossly degrade the "consumer" signal (meaning, signal received by non US military units) within specific areas without having to resort to SA degradation, which is global.

My take on it - as a professional pilot who often flies in conflict areas - is that GPS will probably work just as well there as it will anywhere else, as long as the Americans don't decide to deliberately degrade the signal in a specific area.

For motorcycle touring applications, I really don't think this would present a problem - the worst degradation they would need to apply for military reasons would be probably a 1 km error. In the type of places most of us ride, there are no detailed street level maps available, so we wouldn't really notice any loss of functionality. But for civilian pilots trying to shoot an instrument approach - it's no comfort to know that the signal can suddenly be deliberately degraded, with no notification to the "general public" users.