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GPS Modules

J

Joe G \(Home\)

Jan 1, 1970
0
Hi All,

I am looking for GPS module for handheld unit.

What are the spec's I should look at - to compare modules?

Accuracy?

Number of satellites needed?

other?

Any pointers would be appreciated.


Regards
Joe
 
M

martin griffith

Jan 1, 1970
0
Hi All,

I am looking for GPS module for handheld unit.

What are the spec's I should look at - to compare modules?

Accuracy?

Number of satellites needed?

other?

Any pointers would be appreciated.


Regards
Joe
On a hand held battery powered unit, power consumption and the time to
initialise would be my priorities.


martin
 
P

PeteS

Jan 1, 1970
0
GPS Module specs really don't vary that much.

The place they vary is really the number of correlators onboard the
module memory, time to first fix (TTFF), power consumption, receiver
sensitivity and IO options.
Other things to watch for:
Can it utilise other signals available (such as GSM/3G) to help rough
position itself in very low signal strength areas?

Does it support an active antenna? Note that you have to be careful
about using an active antenna in close proximity to the unit.

The datum used may vary which could affect local accuracy, although
they all seem to use WGS-84 nowadays.


The other thing that varies is price and footprint :)

All GPS modules should require 3 satellites for a fix, 4 for a 'good'
fix as it's inherent in the method used.
Accuracy is really much the same across the modules I have investigated
(I use GPS modules in some products).
There are two accuracy definitions: Absolute accuracy and differential
accuracy. The usual specs are <10m absolute, <2m differential.

All modules should have a serial port that spits out NMEA data for
parsing by an external unit. NMEA is a marine standard, but freely
available.

Cheers

PeteS
 
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