Thread: Technical questions about GPS

GPS signals are carried through waves at a frequency that does not move easily through solid objects. A GPS device relies on a series of satellites in order to determine where it is physically located. The signals sent from these satellites do not penetrate all kinds of barriers with ease. When you use a GPS inside a building, a wide variety of physical barriers and potential interference sources make it difficult for the device to pinpoint your location accurately.
A GPS works better when the device has a clear line of sight to the sky. The more GPS satellites that your personal device can access, the more accurate it is. When inside, there is often no direct line from the satellite signals to your device. The signal weakens or distorts as it travels through the building to your GPS, and the result is inaccurate operation.
The construction materials in a building affect how well a consumer GPS device will work inside. If you're in a house and stand near enough to the windows, or if you're in an office tower with large windows, your GPS could still work. GPS signals pass through glass much more easily than they do through thick, solid materials such as brick, metal, stone or wood.

Today's GPS receivers are extremely accurate, thanks to their parallel multi-channel design.
12 parallel channel receivers are quick to lock onto satellites when first turned on and they maintain strong locks, even in dense foliage or urban settings with tall buildings. Certain atmospheric factors and other sources of error can affect the accuracy of GPS receivers. Newer Garmin GPS receivers with WAAS (Wide Area Augmentation System) capability can improve accuracy to less than three meters on average. No additional equipment or fees are required to take advantage of WAAS. Users can also get better accuracy with Differential GPS (DGPS), which corrects GPS signals to within an average of three to five meters.
Older GPS receivers are accurate to within 15 meters on average.

The next generation of positioning technology is being designed to overcome the limitations of GPS. While GPS devices don't work particularly well indoors, IPS (Indoor Positioning System) technologies are being developed by companies like Google, Microsoft and Nokia to offer pinpoint location accuracy even while users are inside. These technologies utilize different types of signals to triangulate the position of the user while indoors. Wi-Fi hot spots, Bluetooth signals and cellphone signals have all been experimented with by the various companies refining this technology


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It seems you'll need a gps/gprs/gsm tracking device if you wish to track someone's location like that indoors/on a college campus. A standard GPS navigation device such as a Garmin or TomTom PND can't do what you're wanting. Maybe you should check the 'stalker' and privacy laws in your country before proceeding. If you place such a device on their person or in their possessions such as a handbag without lawful reason or without their knowledge then you may be breaking the law depending on who the person is and their relationship to you. Placing a tracking device in your own 8 year old child's schoolbag may not be a problem even without his or her knowledge or permission, but covertly tracking an unrelated college student probably would be.

I doubt that you'll get any meaningful help here for tracking anyone like you want.

I think there are apps like the one you are thinking about

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for example

Originally Posted by Neil

............
I doubt that you'll get any meaningful help here for tracking anyone like you want.

Originally Posted by Ricky239

You misunderstood me. I tend to designing an social college apps which including locations of the students. By the way, i appreciate your reply with much sincere.

Yes I certainly did misunderstand your intentions and rather badly. My apologies and thanks for your polite understanding. Maybe catymag has now also misunderstood you but in a lesser and kinder way , whereas before i think she was on the 'right track' because the apps she mentioned above [and others such as loci etc] i suspect will not give you the super-fine location 'pin-point' accuracy of 'people moving from a table to another in a canteen'. The lead she gave you earlier for Indoor Positioning is probably more to your needs. Afaik, those IPSs can rely on one or more methods of 'triangulation' such as limited-strength wireless networks [WLAN and BT], mobile tower network signals [GSM, 3G, 4G], magnetic and inertial [INS] for fine location and tracking as well as GNSS [GPS etc] and including GPRS, AGPS, DGPS for coarse location.

I now think you are wanting to design and build your own software application for this purpose and want to use GPS-type tracking as the principal indoor location method. Even making use of a SBAS [commonly know as 'WAAS' worldwide but actually usable only in NA] will not give you the fine locating you desire, and in any case i don't think any of those current systems such as WAAS, EGNOS, MSAS etc are usable in Malaysia and regardless the best available will only give about 3 metre accuracy anyway outdoors. Local Area Augmentation Systems [LAAS] involves dedicated fixed ground stations 'correcting' GPS signal errors and distortions but are primarily used for aircraft landing system instrument approaches [IFR] and give better positioning where a large discrepancy is intolerable, particularly vertically]. In short, I don't think any or all GNSS [GPS, GLOSNAS and/or upcoming Gallileo, BeiDou etc] even if enhansed with SBAS/LAAS will be anywhere near sufficient for your purposes, especially indoors when used solely.

So, because you are only looking to locate and track ppl in the confined local situation of your college campus, I think you should look to IPS for your primary location/tracking method as first suggested by catymag. Here's other couple of links:

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As for your campus floor plan, maybe you could get access to the original building plans/site plans or even look to Google maps who are now creating maps for shopping malls and other large public complexes for use with their own IPS. Nokia are also into the act with a BT 4.0 based method of ppl navigating their way around shopping malls and large buildings such as IKEA megastores. If those giants succeed to make it workable quickly and extend it to all public buildings and complexes and also include 'opt-in' tracking, your intended self-developed campus-specific app might be redundant quite quickly perhaps.

Yeah thanks again for the explanation. I'd been into IPS to know more and consider about it before i posted here but i doubt that the IPS is currently mature enough for commercial uses. Somehow its too bad but i knew that the giants are into these far more earlier than i am but its alright because the pinpoint location tracking is just one part of my intended self-developed-campus-specific app, it might be different from what the giants developed so i would go for it on a try.

And i have another questions for that. The link you quoted to me states that Broadcom invented a chip to support IPS for mobile, and i wanted to ask that why is that chip invented for? What is the support they are mentioning for mobile technology which i didn't know. Thanks again.