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one of my friends is thinking of a startup in which we will use GPS technology . The thing is we are thinking of making a cheap gps receiver indigeneously but i am not able to find good links on the internet regarding the in-depth electronic working of the GPS receiver . I have understood the concept of how gps is used to locate a location .

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closed as not a real question by Leon Heller, Phil Frost, placeholder, Nick Alexeev, Dave Tweed Jun 10 '13 at 20:43

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ On what level will you be working? Will you use a standard GPS-receiver and interface it, or do you need to take a deep dive in the GPS system to build the whole receiver yourself (no standard modules)? \$\endgroup\$ – Keelan Jun 10 '13 at 17:50
  • \$\begingroup\$ Either way, this question is too broad. Maybe try reading a datasheet? \$\endgroup\$ – Phil Frost Jun 10 '13 at 17:50
  • \$\begingroup\$ Are you making a GPS receiver or wanting to use one and need to know how to interface with it? (I think this question was closed a little early because of a possible language barrier in communication.) \$\endgroup\$ – user6972 Jun 11 '13 at 4:42
  • \$\begingroup\$ @Camil Staps i needed to ask that , i searched on the internet but i get results only about interfacing the gps but not about how it internally works , and if i search for internal working i get a broad overview about the four satellites . I need to know more about the electronics part of it . \$\endgroup\$ – AbKDs Jun 11 '13 at 11:47
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    \$\begingroup\$ @digi_abhshk More details than what I provided? Are you wanting to to build one or interface with one? There's a steep learning curve that encompasses CDMA radio design, signal processing and some very intense math. \$\endgroup\$ – user6972 Jun 13 '13 at 7:44
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You'll never be able to make a GPS cheaper than the IC solutions that are out there without dumping some money into spinning silicon dies.

But in general GPS is a spread spectrum signal at 1.575GHz. You have to receive the signal then use a variety of PRN (pseudorandom) codes to correlate to the spread signal to de-spread it. (Not trivial). Once you've done that you can receive some of the timing information. However all GPS satellites share the same frequency so your receiver has to process multiple PRN codes on the same signal to find more satellites. Once you have at least 4 you can start processing position information. Trilateration is the most common technique. I've written tools to trilaterate in 3d. The solution is about 3 pages of algebra but it is the simplest. More modern receivers use more complex solutions and there are simulation packages for Matlab you can buy. Wikipedia has a good overview.

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  • \$\begingroup\$ An approximate location can be calculated with only three satellites by using the Earth's surface as the fourth sphere. If the receiver's elevation isn't known, then the precision is very poor by GPS standards, but I know at least my GPS receiver (marketed for hiking/outdoor uses) will display a result in this condition. \$\endgroup\$ – Phil Frost Jun 10 '13 at 19:23
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    \$\begingroup\$ Three satellites provides 2 possible solutions. Your GPS is using information about your previous location to eliminate one of the solutions in lieu of the 4th measurement. In general you need 4 satellites. \$\endgroup\$ – user6972 Jun 11 '13 at 4:38
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I think first you should evaluate some of the GPS Modules from U-Blox and other companies to get their clear working idea. There are different GPS modules for different applications like Dead Reckoning GPS, etc. Round the world there are only few countries which have their GPS Satellites in Space like US and Russia, namely GPS and GLONASS. There are some Taiwan companies also making GPS Modules, you can look into their devices and products to get and idea.

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  • \$\begingroup\$ Similar satellite navigation systems with launched satellites include GPS (USA), GLONASS (RU), Compass/BeiDou (CN) and Galileo (EU) \$\endgroup\$ – RedGrittyBrick Jun 10 '13 at 19:06

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