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| Subject: | Re: [gislist] How about tracking a group of Hikers in real-time? |
| Date: |
07/06/2005 11:15:03 AM |
| From: |
Chris 'Xenon' Hanson |
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Bill Diaz wrote:
> Your biggest challenge would be to design a system which would provide
> coverage over the entire area.
> Hiker Equipment considerations:
> Must be low weight, low volume.
> Must have battery capacity for more than 24 hours.
> Must be water proof.
Seems like you might have to cobble something together yourself.
There are a number of radiomodems out there of varying capability. Operating in the HF
or HAM frequencies you could get decent range. Couple this with some sort of embedded GPS
device and a small microcontroller to poll the GPS and transmit to the radio and you're
good to go. Wrap it all up with batteries and seal it up and dive into the brush. You can
use similar radio modems on the receiving PC.
Of course, it never works that easily, but rolling your own may give you more
flexibility than trying to use someone else's gear.
Another possibility is to use shorter-range radios, but use a repeater in a chase
vehicle to collect and retransmit the data to home base. This would allow for smaller
radios and antenna on the hikers as long as you had bigger antennas (and receiver
amplifiers) on the relay vehicle.
I have a couple of old Metricom 900Mhz radio modems (formerly from the Ricochet
wireless ISP network) that can be set into a mode called STRIP (StarMode Radio IP) where
they form a virtual relay network -- any node receiving a packet of data relays it to the
other nodes who haven't gotten it yet. This allows a node to communicate from A to B to C
even if node A can't reach node C directly.
You can find old Metricom modems very cheap on eBay. If you want to play with a couple,
I'll sell you the ones in basement for whatever the going eBay rate is, I'm done with
them. They are smaller than a paperback book (a little bigger than a pack of cigarettes)
and have an internal battery that they can run on.
--
Chris 'Xenon' Hanson, omo sanze lettere Xenon AlphaPixel.com
PixelSense Landsat processing now available! http://www.alphapixel.com/demos/
"There is no Truth. There is only Perception. To Perceive is to Exist." - Xen
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