You don't know til you try . . .

Project: Multi GPS Tracker

, posted: 8-Feb-2010 20:03

This project started some time ago, (early 2008?) but is finally here. :)

As the name implies it can track multiple GPS units.

The tricky bit was the software.
There are some off the shelf products aimed at fleet management.
I tried to get some going but gave up.
The best candidate ran on linux but my kungfu is not strong there.

So after learning VB6, I wrote my own.
It's pretty no frills at the moment.

-The test site,174.643008&spn=0.002358,0.003954&t=k&z=18


View from point D > C. Not the best case scenario for 2.4ghz rf.

View from point C > B

View from point B > A

A from the clear

At the base station

You can see me driving into the park.
I walk all 3 with me until IO loose the signal and then place the Red unti there.
I then walk around the bush to check signal, no loss.
Down the hill until I loose it near the bottom.
Place the yellow unit.
Down a path, don't get far until I loose it.
Understandable once you see the picture.

The Red unit drifts quite a bit after placement as you can see by the clump of red around it.
Looks like about +-5m.
I forgot to take a pic of placement, it was in a tree, sideways.
So the gps antenna was not pointing up.

The Yellow not so much but probably more due to the fact it was not there long.
5 mins at most.
The Red was there for 13 mins?


A MediaTek MT3329 based module

PAN4561 wireless module, loaded with Synapse Meshing firmware.
Each radio can repeat the signal until it gets to the destination.
The test from A to D would be 3 hops.

How small could it be made?
Comes down to how long you want it to run.
It draws about 3.3v 180mA.
The battery pictured will run it for 6 hrs.
It is a 2s lipo pack which would be reconfigured to 1s2p

The gps can be had as cheap as nz$40 per unit
$35 radio modem module
$5 battery
$5? suitable case.

On the base station side,
$35 radio
$10 USB > RS232 converter
$5? suitable case.

-To do
Adjustable trail length
Smart updating, eg no extra markers if unit is not moving

Since the Radios are 2 way, we could add a screen and send each unit text messages.

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Comment by Ouranos, on 8-Feb-2010 21:07

Interesting mash of technologies.  One potential issue is that the Google Map's terms of use have always prohibited the tracking of vehicles.  The wording has changed from time to time, with the current version being:  "Except where you have been specifically licensed to do so by Google, you may not use Google Maps with any products, systems, or applications installed or otherwise connected to or in communication with vehicles, capable of vehicle navigation, positioning, dispatch, real time route guidance, fleet management or similar applications." (

Author's note by MrWestie, on 8-Feb-2010 21:32

Thanks for the heads up. Note it's not a live link to the google system.
They only got used to extract the aerial photo.
The main application will be tracking people/objects during wargames :)

Comment by d3Xt3r, on 11-Feb-2010 16:40


Some thoughts:

- Did you use any external GPS antenna, or have considered using one? It would be interesting to see how much difference it would have made.

- How do you plan solve do the 'smart updating' bit. Personally I've thought of using an accelerometer..

Author's note by MrWestie, on 12-Feb-2010 07:53

Currently using the onboard antennas. I am sure an external would have helped as it could be easier to keep it pointed skyward. But that will add and extra thing to snag/fall off.
The movement sensing could all be done in the tracker sw. If the object does not move 10m from it last average 5 position then consider it stationary.
An accelerometer will not help if it's attached to a person. For something like a box it should work.

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