how to get GPS data

ivica

When I use PMB 648 GPS receiver, I always get my latitude & longitude data is null (0000.000,N & 0000.000,W). I only get my UTC data. Do you have any explanation about this problem? thanks....

Post Edited (ivica) : 4/26/2010 8:42:53 AM GMT

hover1

Are you trying to use it inside? Is the LED flashing or on steady?
It normally will not work indoors. The LED has to be on steady indicating that it has aquired at least 3 satellites.

hover1

They will sometimes take 3-5 minutes outside (with clear line of sight) to aquire the satellites. Mine is 2-3 minutes on average.

sylvie369

I've been working this morning with a GPS module that I received just last week. In my experience, it takes much longer than most modules claim to get a lock, at least when they're first turned on.·I've spent much of the morning looking at data that look like what you're describing (correct time, null position), before eventually getting good position data. Patience - turn it on and then go do something else for a while.

hover1

Cold start in a brand new position is much longer than some of the quoted times. Once it has aquired enough satellites for a fix, the next time you start it up in the same location the fix is faster.

I believe the UTC time can be gotten from 1 satellite, so that's why it shows up first.

hover1

"In the GPS receiver (PMB 648) data sheet, explained about Acquisition
Time:
Cold Start: 42sec (Average)
Warm Start: 38sec (Average)
Hot Start: 1sec (Min.)

Can you help me what the meaning of Acquisition Time. Thanks...

ivica"

It is the time to aquire at least 3 satellites in a best case senario (very open field with no overhead objects).

You should delete your other posting as is against forums rules to double post. Edit your other posting and use the red X.

BTPost

Typically, GPS Receiver Black Boxes will output Data every Second, as soon as they Power on Initialize... With Null Data in the Output Stream. The First Data to be Output will be UCT Clock Time, and this happens when the FIRST Valid Data Packet is decoded from the Data-stream acquired from the First SAT. Then the GPS MUST Download a Lengthy set of Data (Almanac) that gives the positions of the SAT's that should be Above the Horizon, and receivable. Once that has been decoded successfully, then the GPS will look for, acquire, and decode the Data-stream from those SATs it can Hear that are above the Horizon. As these SATs are Acquired, Valid 2D Lock, will be shown by Valid Lat-Long Data Output, instead of Null Data in the Output Data-stream. When four SATs are Locked, then the GPS will show the 3D Flag, and start Calculating COP and the other Quality of Signal information in the Output Data-Stream, instead of Null Data in those Frames. Quality of Signal at the Antenna will determine UTC Clock Lock, 2D Lock, and 3D Lock. If your signal is POOR, your Lock-up times will be longer, than if you Signal quality is high or good. Most GPS's will constantly be updating the locks on various SATs as the become available and drop those as they fall below the horizon, all the while maintaining valid locks on at least 4 SAT's so as to maintain 3D lock.

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Bruce in alaska