GPS related Queries

GPSTech · Occasional Visitor Joined: Apr 04, 2007 Posts: 8

Hi,

I am carrying out some kind of feasibility study in GPS technology and have few questions...

1. Where on earth will GPS work? Closed places? only open places? Will GPS work in the closed room of a building?

As I understand, GPS receiver should be able to see at least 3 satellites...In the absence of which, it wont work...I would like to know, does this work only at those places where there is no cover on top...Could people use GPS in like caves, tunnels etc? If somebody is covered under ice due to some storm and he is carrying a GPS receiver, would it be possible for others to track him?

2. How difficult or easy it is get the information continously on the GPS from the centralized server in the absence of any other communication signal...I mean real time data? Is it possible to use GPS as a communication channel?

3. Is it possible to locate the position of other people on one GPS device in the absence of any other communication signal? Will it work where there is no mobile signal? Are there any devices in the market which does that?

4. How do 2 GPS devices talk to each other? Is it possible to make 2 GPS devices talk to each other?

Thanks a lot in advance.

Cheers

mikealder · Posted: Wed Apr 04, 2007 5:04 pm Post subject:

1/ The GPS receivers will generally only work in the open, newer devices may work inside a building assuming sufficient signal can propagate through the structure, use underground or in caves etc will not work without the use of specialist equipment to re-radiate the signal in the area of use. The Re-Rads were deemed illegal last year (UK) as they transmit in a frequency band that would require a license, other than military usage etc.

A GPS device is only a receiver, it cannot transmit position - to do this requires the use of other technology, often GSM or mobile phones can be used to transmit the position data to another device, user or PC.

2/ GPS cannot be used for communication, see the second part of my answer above.

3/ Without a method to transmit the location others would not be able to locate the device

4/ GPS devices do not communicate between each other, to do this requires Radio/ mobile phone and a data connection - Mike

GPSTech · Occasional Visitor Joined: Apr 04, 2007 Posts: 8

Thanks a lot Mike for all the answers...I highly appreciate it...

Could you tell me are there any GPS devices currently in the market which can locate the position of other GPS devices? I guess there are some but not sure...Could you please confirm this...Also, if there are what technology do they use to make this feature work...I mean are they using radio signals or mobile signals...The only problem with mobile signals, I think, is accessibility of mobile signals...There is still lot of geography where there are no mobile signals...How can we use radio signals? Is it good enough and easy enough to implement the same functionality using radio signals?

Also, could you tell me the resolution of the GPS devices. How accurately can they locate the position of the object...Are there any readymade applications which can be used in GPS enabled phones to map some location on GPS enabled mobile phones....

I know they are lots of questions....I might ask few more after getting your answer...Highly appreciate your time and help...

Thanks

mikealder · Posted: Wed Apr 04, 2007 9:41 pm Post subject:

The only way to locate a GPS receiver is if it transmits its position using GSM mobile phone (easy to do when the signal is available) or radio, PMR sets should be capable of doing this over a limited range, but its very much a home brew creation, I have not seen radio transmission equipment that is dedicated to GPS location as yet, it probably exists but too specialist, either military or rescue services.

Sending positional data over the radio could be as simple as using dots and dashes, or more complicated via digital signalling - again home made, using home made software.

Positional accuracy you can get 3M, but work on 10M and you won't be too far out, weather can affect the signal and therefore degrade the accuracy, but it’s still not bad considering the distances involved and the power levels of the actual GPS sats in orbit.

There are devices that can track other receivers, but they are dependent upon the software and mobile phone connection, TomTom offer this capability via the "Buddy" system, Co-Pilot also allow tracking, as do Route 66, but this is software that is dependent upon the necessary hardware and GSM connection.

Other options are dedicated tracker units employing GPS, again these rely upon GSM mobile phone for real time tracking.

Perhaps it would assist to be more specific with your aims, what are you trying to do, and what areas are you looking to use GPS in? Under ice and down caves seems a little extreme, it’s certainly not the norm - Mike

GPSTech · Occasional Visitor Joined: Apr 04, 2007 Posts: 8

Thanks again...Will certainly come back to you with some more queries...

roswellgrey · Posted: Thu Apr 05, 2007 1:54 pm Post subject:

In case you haven't seen it, Garmin have short range, RF based location functionality in the Rhino

http://www.garmin.com/products/rino/positionReport.html

US/Canada only...

GPSTech · Occasional Visitor Joined: Apr 04, 2007 Posts: 8

Hi Mike:

I am back with few more questions...

Actually I am trying to make use of GPS receiver which is available these days on few mobile phones. Would it be possible for you tell me few things related to that...They are as following:

1. What is the ratio of mobile phones which have GPS receiver built in currently. Also, what is the outlook for the future.
2. what is the strength, accuracy and resolution of the the kind of receivers that come in Mobile phones these days. Again what kind of outlook can be provided regarding the same features.
3. Would there be any web resource, where I could learn more about the same technology, its usages, its positive points, its negative points and all those sort of things...

Thanks a lot Mike in advance...I highly appreciate the time and effort you are putting in my questions.

Avroy · Occasional Visitor Joined: Apr 14, 2007 Posts: 6

very useful talk for beginers like me..

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