Hi All,
Apologies if this is too off topic for the group but here it goes.
I've been filling in some time at the Australian club/sports class nationals
(crewing) by looking into and testing some live tracking options. I'll
outline what i've tried and found, perhaps some will find it interesting.
I know there are some commercial tracking products, such as the fairly
popular SPOT tracker (in australia anyway), however i was curious to see
what can be done with the newer mobile phones. Most newer smartphone type
handsets have quite a few sensors. GPS, Compass, Accelerometers etc, as well
as access to the internet via 3g. I have available a HTC Desire (Android
2.2) and an Iphone 4, so they were the phones i played around with.
The two main bits of software i had success with were:
Option 1:
-------------
Instamapper (www.instamapper.com)
Cost: Free
Supported Platforms: Android, IPhone, Blackberry
Quickest possible data point refresh rate: 5 seconds
This is by far the easiest to setup. It involves registering an account on
the website, installing the app on the phone, generating a key (unique
identifier) on the website, entering the key in the app's settings and you
are good to go. It gives you a fairly decent interface, with the track being
overlayed on google maps. The statistics for each data point you can see is
Latitude, Longitude, Altitude, Speed, Bearing, Time.
The advantage to this method is that it's effectively clientless for crew
etc. We had 3-4 different people across the state watching various flights
live, none of them particularly computer savvy.
It does also provide a basic API, allowing easy access to the latest data
point, or optionally the last X datapoints. This is done via simple HTTP
requests, which are documented on the website. I managed to throw together a
script (Kixtart - only language i'm semi competent with) which every 10
seconds polls the instamapper site using it's API to get the last datapoint,
and add it to a KML file.
Using the information provided from the API it was also possible to easily
produce some other statistics such as climb/sink rate since last datapoint.
The end result being the trace appears in google earth (3d) in close to
realtime. If anyone wants the source, shoot me an email, it's nothing fancy.
Option 2:
------------
Application: GPSd
Cost: Free (GNU, Open source i think)
Supported Devices: As far as i can tell, only android has an easy to install
GPSd Server component. I think with Iphones it is possible, but invovlves
jailbreaking them and a fair bit of command line work.
Quickest possible data point refreshes: I think as quick as the GPS can
generate them - i was getting 1 every second.
This method involves quite alot more work than option 1, and probably isn't
a very good method. However it does allow 1 second refreshes and the end
result allows you to effectively have a carbon copy of what the pilot sees
on their PNA/PDA - XCSoar running on the desktop with the gps source being
the phone's gps in the glider.
GPSd is an open sorce project that can and has been ported to android that
basically creates an open port on the host device, and is able to relay the
raw output of the GPS to this port in plain text. For instance you can
telnet to the phone on that port and see the NMEA sentences, similar to what
you would get if you turned on Raw logging in XCSoar and looked that the
output file.
XCSoar requires a serial port to obtain it's NMEA sentences (GPS data), so
the trick is then to create a virtual com port mirroring the contents of the
telnet session. I was able to do this with a free product called Franson GPS
Gate. The end result was i had a working copy of XCSoar on my laptop showing
live data from the glider. From this i was able to see most stats - final
glide, vario, L/D, altitude, speed, task etc.
This method was quite alot of work. The service provider appears to NAT the
3g internet traffic from the phone. Because GPSd requires direct tcp access
to the phone, port forwarding needs to be used. To do this i used a VPN
provider ($10/month) to give the phone a publicly accessible IP Address, and
then request the VPN Provider open the required port.
--------------------------------------------------
Phone 3g reception was suprisingly good. I think the longest time i've seen
between datapoints is about 6 mins, which is pretty good really. I'd
estimate about 70% of the datapoints make it through over the duration of a
flight. This is done without any passive/active antenna boosters etc, which
would likley improve this.
If anyone wants to try anything like this, keep in mind it does run the
battery of the phone down pretty quick - a few hours will run it flat. I
wired a female car-type socket into the car and used a 12v phone charger.
Anyway, just thaught i'd jot down what i've found, it might save someone
reinventing the wheel.
Luke
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