The idea in a nutshell
- create a tracking device that can be used in gliders and other aircraft, compatible with OGN network receivers.
- oriented towards position reporting and long reception range, not towards collision detection.
- is cheap! Making the hardware easily affordable is essential for this device to be successful.
- is using an open protocol - OGN tracking protocol (OGNTP).
- is relaying position messages e.g. from other aircraft flying lower to help to locate outlanfings.
More on technical requirements
- should be powered with internal rechargeable batteries (e.g. AA NiMH batteries, or "Nokia" Li-Ion type battery, like e.g. Nano logger) + it must have the possibility to be plugged easily into glider's cabling (RJ-11 or RJ-45 plug)
- must be small, lightweight and easy to install!
- should be able to use max. allowed transmission power on its dedicated frequency (up to 25mW?)
- Should have black casing - to avoid reflects when installed on the instruments board.
- could have microSD card slot and could be logging IGC files.
- could have miniUSB port to recharge it (+ it could be recognized as USB drive by a PC ?)
- RJ-45 could serve both: as power entry + RS-232 (like Volkslogger)
- could have Bluetooth module, to pair it with a smartphone, or a PNA/PDA (like e.g. in case of Nano logger)
- any other requirement ?
(Non)Compatibility with FLARM
OGN tracker is not compatible with FLARM. It transmits packets on a different (yet close) frequency and with different format thus OGN packets can not be received by a FLARM unit. Incompatibility is on a hardware level: nRF905 RF chip used by FLARM uses specific preamble which is different from one used by RF chips used by OGN. However, OGN stations based on DVB-T SDR radios and software processing are able to demodulate and decode packets received from both OGN trackers and FLARM units.
The work is undergoing! Please refer to the following documents for more details:
- OGN tracker design document by Sylwek.
Additional design documents:
- Open ogn-tracker code exists.
I produces packets in OGNTP format (on 8-bit AVR and 32-bit ARM CPU's) and sends them through using SPIRIT1 RF chip.
- Tests with CC1101 RF chip were done and successful!
- Tests with RFM69 RF chip are underway.
A bit of history
The core developers involved in the "OGN tracker" project are not newbies in the subject of glider tracking systems. They have got experience working on a similar solutions over past years. In 2008, at ZAR (Poland), a small group of friends and glider pilots started a tracking project with the aim of creating a low-cost and working solution for the upcoming Sailplane GP event.A link to the original presentation from 2008 (only available in Polish ): ZarBrick project
Thee is also a version in English, based on the original one and presenting the basic concepts of "early" OGN. It also refers to Zarbrick project and the tracker.
ZarBrick tracker prototype
Although OGN uses different technology, it is important to note that several interesting concepts where already discussed, proposed and implemented in 2009, such as e.g. message relaying between trackers increasing coverage. These ideas are now being implemented and extended by OGN tracker.
Assembly in progress!
GPS connected, still a few elements missing.
- in idle 50mA - from which 15mA is taken by the CPU (for now unlimited) - that can most likely be reduced to 5mA. It gives ~24h operation time.
- in the "soft power off" state - 100uA - quite significant, but taking into account the battery (1350mAh) the discharge time is long enough.
- March 2015:
Time to start soldering the components!
- Janurary 2015:
More OGN tracker field testing were conducted!
I selected two hills that are visible from EPZR station.
Results are positive:
Prusow hill (23.3 km): signal to noise = 20 dB.
Bendoszka Wielka (42km): S/N over 10dB (maximum 15) - packet reception was stable.
- December 2014:
Hi. I want to share some news about OGN tracker.
We created two prototypes combined from different modules prepared previously (pictures below).
Although it looks funny, with such prototype we could solve most of design problems and also prepare software.
Prototype consists of:
- Nucleo board with STM32L152,
- Spirit1 module (our design),
- A2235-H GPS module (our design),
- Li-po battery and charger.
Tracker consumes 50mA and works (transmits) at least 18 hours on 950mAh battery, but it could be improved to 40mA at least.
We already have positive RF measurements results from lab, but after all we wanted to see some real life results.
Using EPZR dual mode station we found two places 3 and 10 km away that offered line of sight to antenna (unfortunately no flights were possible during testing day).
3km distance results - Tresna dam:
30mW transmit power on short antenna: S/N ratio: 30dB,
30mW transmit power on long antenna: S/N ratio: 33dB.
10km distance results - Soła river bridge near Żywiec.
We drove two times over the bridge - with short and long antenna. Tracker was attached to side window in our car.
Surprisingly results are similar - 3dB difference from 3km point isn't clearly visible this time.
Overall: signal is strong and we are expecting way more than 10km range.
Our next goal is to prepare one PCB version of the OGN tracker prototype. Most of design decision are made now, software is emerging too:
First version will be very simple (and cheap), because we want to sure that we prepare something for incoming 2015 season.
It could be called - "reference design" for other designers if they want to prepare it's own compatible trackers.
Please note that Spirit1 module could also receive other OGN trackers - we will experiment with packet relaying for increased range.
- November 2014: Preparing for tests in the terrain!
More news + some photos of the OGN tracker - soon!
- October 2014: First working version of OGN tracker prototype was presented in Krakow, Poland. Big Thanks and Bravo to our colleagues Sylwek and Leszek! Great job!
Setup used for the demo:
- OGN tracker
- Condor Competition Soaring Simulator serving GPS NMEA data to the OGN tracker.
- standard OGN receiver, running on Fujitsu/Siemens Futro terminal computer
- visualization in live.glidernet.org and FR24
- Demo team flew from EPZR:
More information here