[neilep]

Hang On, if you are on the moon...do you really need your GPS to tell you that......you're on the moon ?

How else would you find the nearest McDonalds?

Easy.
Find the place with no atmosphere.

 [ Invalid Attachment ]

[chris (OP)]

Why Mcdonalds? In space you'd go to...Starbucks, surely?

[Jolly- Joliver]

Syhprum - you are quite correct about the satellites.  But how do they broadcast their signal?  It would not take much leakage for the signals to be receivable on the moon.  And three or more signals and a decent software algorithm and you have an exact position. 

So - If you were on the dark side of the moon (when you are part of the great gig in the sky) I think you would be unlucky - but on the side that faces the earth I reckon a decent receiver could pick up enough signals to make a fairly reasonable approximation.

Sorry but the satalites that work for GPS are desined for the earth, first, they do not face the moon secound, third they work by trianglurisationaslism so you would need atleast two or three satalites to be involved, and also for those satalites and your GPS devices sofware to have a complete map of the moon.

Never going to happen, not forgetting all the time it would take for any signal to arrive from the moon to any satalite orbiting the earth.

[Bored chemist]

"Sorry but the satalites that work for GPS are desined for the earth"
The clocks in the satellites would run correctly on earth. They are designed for space.
" they work by trianglurisationaslism so you would need atleast two or three satalites to be involved,"
There are 31 so, from the near side of the moon you could typically see a dozen or more.
"and also for those satalites and your GPS devices sofware to have a complete map of the moon."
Nope, you can use a coordinate system based on earth anywhere, including the moon.
"Not forgetting all the time it would take for any signal to arrive from the moon to any satalite orbiting the earth"
That delay is exactly how the system works.

[Jolly- Joliver]

"Sorry but the satalites that work for GPS are desined for the earth"
The clocks in the satellites would run correctly on earth. They are designed for space.

I was talking about the systems themselves being used with distances and time delays, that are set for earth, it's a given that satalites are designed to work in space.

 

" they work by trianglurisationaslism so you would need atleast two or three satalites to be involved,"
There are 31 so, from the near side of the moon you could typically see a dozen or more.

A dozen or more:- facing the earth.

"and also for those satalites and your GPS devices sofware to have a complete map of the moon."
Nope, you can use a coordinate system based on earth anywhere, including the moon.

You mean based on a sphere shape, except that the all spheres are slightly different in proportions, not forgetting that valleys and mountains also will effect the position of a person. You would need a complete map of the moon to get a correct GPS positon, and satalites arrounds the moon also to get a correct position.
 http://en.wikipedia.org/wiki/Global_Positioning_System

The receiver uses the messages it receives to determine the transit time of each message and computes the distance to each satellite. These distances along with the satellites' locations are used with the possible aid of trilateration, depending on which algorithm is used, to compute the position of the receiver. This position is then displayed, perhaps with a moving map display or latitude and longitude; elevation information may be included. Many GPS units show derived information such as direction and speed, calculated from position changes.

"Not forgetting all the time it would take for any signal to arrive from the moon to any satalite orbiting the earth"
That delay is exactly how the system works.

No, there are a few ways a GPS system can work, yet we are talking about the one we use.

"However, even a very small clock error multiplied by the very large speed of light — the speed at which satellite signals propagate — results in a large positional error. Therefore receivers use four or more satellites to solve for the receiver's location and time."

And sending a signal from the moon to a satalite arround the earth would take too long, besides the fact that they are designed to communicate with systems on the earth.

Although four satellites are required for normal operation, fewer apply in special cases. If one variable is already known, a receiver can determine its position using only three satellites. For example, a ship or aircraft may have known elevation. Some GPS receivers may use additional clues or assumptions (such as reusing the last known altitude, dead reckoning, inertial navigation, or including information from the vehicle computer) to give a less accurate (degraded) position when fewer than four satellites are visible

[Bored chemist]

To say "I was talking about the systems themselves being used with distances and time delays, that are set for earth, it's a given the satalites are designed to work in space."
implies that you already know that answer, I contend that you don't.
Of course, the system was designed to work on earth. So, in a sense, were people. But they still worked on the moon.
There are plenty of instances of things designed for one thing but used for others. The internet wasn't designed for distributing naughty pictures, but that's one of its major uses.

As for "A dozen or more:- facing the earth.", do you not realise that, for one thing , these were designed to spread a signal pretty much from horizon to horizon, and for another, antennae never form "perfect" beams- there's always some transmission in other directions?


"You mean based on a sphere shape,..."
No, I meant what I said.
A coordinate system based on earth (the one I had in mind was latitude, longitude and altitude) which can be used to pinpoint any place in the universe. Please don't presume to tell me what I mean.

"No, there are a few ways a GPS system can work, yet we are talking about the one we use."
There may be several ways you could set up a GPS system.
The one we use depends explicitly on exactly the time delays that you seem to think are a problem.

"And sending a signal from the moon to a satalite arround the earth would take too long, "
Too long for what? The delay would be less than two seconds. How much of a hurry are you in?

"besides the fact that they are designed to communicate with systems on the earth."
Still not important. It's not an issue of what they were designed to do, the question is about what they could do.

In principle, with the right decoding (normally restricted to military systems), a big enough aerial and the right software, you could find out your position on the moon by reference to the GPS system. The problems would be that it would give a result in earth based coordinates. But that's still telling you where you are. The other problem is that the accuracy would suck. That's not the same as saying it wouldn't work.

[imatfaal]

And would the accuracy even suck? It would be worse than on the surface of the earth but you would have a dozen or more points, with separations between them of up to 50,000km (they are in 20,000 km orbits) from a distance of around 400,000 km.  The maths is beyond me, even if I did know what the inherent error margin were, but it doesn't strike me as too bad a deal - especially if there was no alternative.

[Geezer]

And would the accuracy even suck? It would be worse than on the surface of the earth but you would have a dozen or more points, with separations between them of up to 50,000km (they are in 20,000 km orbits) from a distance of around 400,000 km.  The maths is beyond me, even if I did know what the inherent error margin were, but it doesn't strike me as too bad a deal - especially if there was no alternative.

The accuracy is a function of the angles formed at the GPS receiver between three or more satellites. The greater the angles, the more accurate the measurement. As you might imagine, the angles become rather acute when the receiver is on the Moon, so the accuracy won't be good.

I would think the accuracy is a function of the cosine of the angles formed between satellites and the receiver, so a small error in the lengths of the adjacent sides of the triangle produces a relatively large error in the resolved angle when that angle is small.

[Jolly- Joliver]

To say "I was talking about the systems themselves being used with distances and time delays, that are set for earth, it's a given the satalites are designed to work in space."
implies that you already know that answer, I contend that you don't.
Of course, the system was designed to work on earth. So, in a sense, were people. But they still worked on the moon.
There are plenty of instances of things designed for one thing but used for others. The internet wasn't designed for distributing naughty pictures, but that's one of its major uses.

As for "A dozen or more:- facing the earth.", do you not realise that, for one thing , these were designed to spread a signal pretty much from horizon to horizon, and for another, antennae never form "perfect" beams- there's always some transmission in other directions?

That's very nice, but those directions are not 180 degree. Leaving only satalite on the other side of the earth(realtive to the moons position at the time) being able to send a signal in the moons direction at all, very hit and miss, if returned I think you'll find the satalite that sent it could have moved into a non reciving postion. plus the angles could send any signal retuen in a tottally different direction. Hoirson to horison or not it's not so clear sent signal would reurn to the satalite that sent them, your asking a satialite to perform a function it has not been tuned to doing. 

"You mean based on a sphere shape,..."
No, I meant what I said.
A coordinate system based on earth (the one I had in mind was latitude, longitude and altitude) which can be used to pinpoint any place in the universe. Please don't presume to tell me what I mean.

"No, there are a few ways a GPS system can work, yet we are talking about the one we use."
There may be several ways you could set up a GPS system.
The one we use depends explicitly on exactly the time delays that you seem to think are a problem.

"And sending a signal from the moon to a satalite arround the earth would take too long, "
Too long for what? The delay would be less than two seconds. How much of a hurry are you in?

Not going to matter if only one or two can pick it up, besides the distance would be greater, as the closest satalites to the moon wouldn't be able to transmit.

 

"besides the fact that they are designed to communicate with systems on the earth."
Still not important. It's not an issue of what they were designed to do, the question is about what they could do.

They could do lots of things, if we are talking about "coulds" then fine. Yes one day they could gives us gps on the moon.

In principle, with the right decoding (normally restricted to military systems), a big enough aerial and the right software, you could find out your position on the moon by reference to the GPS system. The problems would be that it would give a result in earth based coordinates. But that's still telling you where you are. The other problem is that the accuracy would suck. That's not the same as saying it wouldn't work.

If it's in accurate it isnt working.

[Geezer]

I think you'll find the satalite that sent it could have moved into a non reciving postion

It doesn't matter if the signal disappears. The GPS receiver only needs to receive the satellite's signal once to determine a position.

You might want to take a look at this  http://en.wikipedia.org/wiki/Global_Positioning_System#Basic_concept_of_GPS

[Jolly- Joliver]

I think you'll find the satalite that sent it could have moved into a non reciving postion

It doesn't matter if the signal disappears. The GPS receiver only needs to receive the satellite's signal once to determine a position.

You might want to take a look at this  http://en.wikipedia.org/wiki/Global_Positioning_System#Basic_concept_of_GPS

I referenced that link: "Although four satellites are required for normal operation, fewer apply in special cases. If one variable is already known, a receiver can determine its position using only three satellites."

You are saying a device having recieved just one signal from one satalite while on the moon, will be able to tell you where you are. Not the case.

It might be able to say: "You're on the moon"

[Geezer]

You are saying a device having recieved just one signal from one satalite while on the moon, will be able to tell you where you are.

No. I am not saying that at all. I am saying the receiver only needs to receive one transmission per satellite. Your point about the satellite moving is irrelevant.

[Jolly- Joliver]

You are saying a device having recieved just one signal from one satalite while on the moon, will be able to tell you where you are.

No. I am not saying that at all. I am saying the receiver only needs to receive one transmission per satellite. Your point about the satellite moving is irrelevant.

They are designed to transmit to the earth, the moon is in the other direction to normal opperation. Personally I think only around 10% of the satalites up there at any one time could really transmitt in a luna direction anyway, that' 2.3 satalites but maybe it 20% that would 4.6 satalites.

Best case I see is 4.6 being in a position to do so but there is no garentee that would actually work, besides as I said before the program on the GPS device would have to have a map and record of the moon, to then place you with in that map.   

[Geezer]

Now look here Wybit, either admit you were wrong and you have learned something, or provide some substantial evidence to support your arguments. It looks like all you are doing is trying to change the subject whenever you are challenged.

Sorry, but that's nothing but trolling. You can learn a lot on TNS (I have), but if you are confident you are always right, you are simply being a troll.

It's your call. Are you trying to prove something, or are you trying to learn anything?   

[syhprum]

NASA have already acknowledged that to use the Earths GPS system for navigation on the Moon is all but impossible and to set up a similar system to cover the moon would be extremely expensive.
To this end they have let contracts to private companies to develop simple short range systems that will assist navigation on the moon.

http://www.thaindian.com/newsportal/world-news/nasa-developing-navigation-system-for-moon-lead_10074436.html

[Bored chemist]

"Personally I think only around 10% of the satalites up there at any one time could really transmitt in a luna direction anyway"
Odd that, because, in reality, about half of them would (though the signal strength would be poor).
When you say "it's not so clear sent signal would reurn to the satalite that sent them," are you labouring under the delusion that GPS sends a signal back to the satellites? The GPS receivers are just receivers, not transmitters.
In other words, do you know what you are talking about? If not, perhaps you might think about learning rather than trolling.


Incidentally, if you use Google chrome as a web browser it highlights spelling errors for you. That way you don't end up pontificating about satellites without even knowing how to spell the word.

[Jolly- Joliver]

Now look here Wybit, either admit you were wrong and you have learned something, or provide some substantial evidence to support your arguments. It looks like all you are doing is trying to change the subject whenever you are challenged.

Not the case at all. It is you and others that claimed that it would work. I disagreed from the beginning.

Sorry, but that's nothing but trolling.

You know what they say about insulting people.

But to clarify, The question was "Would my GPS work on the moon"

I said no, and that the satlites signal would not get there, that also the device needed a map of the moon to work at all.

Bored Chemist said no you didn't need a map and that GPS could tell you where you were any where in the universe.

He and others said that the signals from satellites, could get there, I replied to that no if that was possible I think "Think" only 10% of the satellites could do that- think, not a statement of fact, what I believed, based on the idea that the signals could get there, and the people making those assertions never backed up there claims with any evidence either I might like to point out.

In fact other than you Geezer I am the only one that actually referenced another site, and the site you reference was the one I did.

But as always there is a mis-communication, and misunderstanding.
 

You can learn a lot on TNS (I have), but if you are confident you are always right, you are simply being a troll.

It's your call. Are you trying to prove something, or are you trying to learn anything?   

I'm trying to answer the question, you all seem to think it would work, I disagree.

As I said before to work it would need a map of the moon

http://www8.garmin.com/aboutGPS/

Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map.

This alone is enough to show that a GPS on the moon would not function, let alone be able to plot your position anywhere in the universe.


Another issue with the signals is solar winds which disrupt them, Still looking for the reference for that, but I did read it some where.

Other than that, the Next generation of GPS- WAAS is looking to increase the signal foot print of the GPS system http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System

But even if the current signal was Horizon to horizon as Bored chemist claimed, it would not be beyond that would it, it would concentrate it's signal foot print or zone of sight, to perform it's function in the optimal manner, and that function is on the earth and for the earth, Why waste signal out into space?

 GPS started in 1978 I am not sure what the actual signal foot print is, but the technology from when it started is clearly dated today
http://www.apsattv.com/techinfo/predicting-out-of-footprint-coverage.htm

Site on satellite coverages- footprints and receptions outside of the signal foot print.

also on the signal front
http://www8.garmin.com/aboutGPS/

◦Number of satellites visible - The more satellites a GPS receiver can "see," the better the accuracy. Buildings, terrain, electronic interference(which I believe includes solar wind interference), or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. GPS units typically will not work indoors, underwater or underground.

Should add or in space I think really.

"Personally I think only around 10% of the satalites up there at any one time could really transmitt in a luna direction anyway"
Odd that, because, in reality, about half of them would (though the signal strength would be poor).

Based upon what do you make that acertion? AS things stand I don't think any would.

When you say "it's not so clear sent signal would reurn to the satalite that sent them," are you labouring under the delusion that GPS sends a signal back to the satellites? The GPS receivers are just receivers, not transmitters.

I think you'll find the latest ones do blackberry and such like.
http://us.blackberry.com/smartphones/features/gps.jsp

But that is an assumption, Hence think.

In other words, do you know what you are talking about? If not, perhaps you might think about learning rather than trolling.


Incidentally, if you use Google chrome as a web browser it highlights spelling errors for you. That way you don't end up pontificating about satellites without even knowing how to spell the word.

Bored Chemist I have seen you make spelling mistakes also, Seriously poor show.

[Jolly- Joliver]

NASA have already acknowledged that to use the Earths GPS system for navigation on the Moon is all but impossible and to set up a similar system to cover the moon would be extremely expensive.
To this end they have let contracts to private companies to develop simple short range systems that will assist navigation on the moon.

http://www.thaindian.com/newsportal/world-news/nasa-developing-navigation-system-for-moon-lead_10074436.html

Interesting looks like they are going to develop one.

[CliffordK]

So - If you were on the dark side of the moon (when you are part of the great gig in the sky) I think you would be unlucky - but on the side that faces the earth I reckon a decent receiver could pick up enough signals to make a fairly reasonable approximation.

Why wouldn't it work on the dark side of the moon facing earth?

The "Dark Side of the Moon" has nothing to do with the sun or illumination.
Rather, the moon is tidally locked with the earth.  One side of the moon always faces the earth.  One side (the dark side) always faces away from the earth.  Thus, if you were on the side of the moon facing away from Earth...  the GPS satellites would be useless.

As far as whether you could use a GPS system.
Obviously any software pre-programmed to positions on earth would be confused.

Are the antennas omni-directional antennas?  

I don't see why you couldn't make basic triangulation routines to map a position in space above the satellites...  and then map that onto the lunar surface based on lunar topography and the lunar orbit.

A time delay is irrelevant, and would just be part of the calculations.  The geosynchronous orbit is about 36,000 km.  The moon is at about 385,000 km.  It is likely one could pick up satellites on all sides of the earth that are not eclipsed by the planet. In fact, using the satellites on the far side of Earth, one should be able to pinpoint a location 385,000 km below the surface of the planet.

You can use GPS equipment in conjunction with a base station at a fixed location.  Putting a fixed base station on the moon would likely greatly simplify the calculations, and significantly improve the accuracy of the system.

Ahh...
This base station would be essentially one approach for doing the local triangulation.  One might be able to use the base station for calculating the offset even while not in direct sight of the base station.

[Jolly- Joliver]

So - If you were on the dark side of the moon (when you are part of the great gig in the sky) I think you would be unlucky - but on the side that faces the earth I reckon a decent receiver could pick up enough signals to make a fairly reasonable approximation.

Why wouldn't it work on the dark side of the moon facing earth?

The "Dark Side of the Moon" has nothing to do with the sun or illumination.
Rather, the moon is tidally locked with the earth.  One side of the moon always faces the earth.  One side (the dark side) always faces away from the earth.  Thus, if you were on the side of the moon facing away from Earth...  the GPS satellites would be useless.

As far as whether you could use a GPS system.
Obviously any software pre-programmed to positions on earth would be confused.

Are the antennas omni-directional antennas?  

I don't see why you couldn't make basic triangulation routines to map a position in space above the satellites...  and then map that onto the lunar surface based on lunar topography and the lunar orbit.

I dont know why you would need the luna orbit, to work it out.

A time delay is irrelevant, and would just be part of the calculations.  The geosynchronous orbit is about 36,000 km.  The moon is at about 385,000 km.  It is likely one could pick up satellites on all sides of the earth that are not eclipsed by the planet.

No I dis agree, The satalites set a signal zone an area they cover, I'm still looking for the exact size but, as the signal travel through the atmosphere it is distorted, meaning that signals that travel through and back out will be even more distorted, Besides I do not believe that really any signals travel out side of a zone of the earth they are designed to cover, there might be a very low frequency at the zone edges.

 In fact, using the satellites on the far side of Earth, one should be able to pinpoint a location 385,000 km below the surface of the planet.

Below the surface? What do you mean? GPS do not work indoors.

You can use GPS equipment in conjunction with a base station at a fixed location.  Putting a fixed base station on the moon would likely greatly simplify the calculations, and significantly improve the accuracy of the system.

Ahh...
This base station would be essentially one approach for doing the local triangulation.  One might be able to use the base station for calculating the offset even while not in direct sight of the base station.

The base staion would have to talk to the device. Personally I think for the size of the moon just 8 satalites, 4 for each face should be enough, but they would have to orbit the moon tho.

If you wanted to use the earths GPS satalites I think you would have to turn them to transmit straight at it, even then there is no garentee, Just look at the earth GPS system if you're indoors with four satalites in a good postions it wont work. Using the ones we have at the moment in there current function is just not possible, plus you would need your GPS to have a moon map also.