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Kite Altitude World Record
Global Positioning System & Telemetry
Just 20 years ago GPS was for the military or the privileged few. In fact it was developed by the US military to enhance their operations including navigation, battle strategy, weapons deployment, asset tracking and troop location. It's full capabilities were only made available to the public after commercial interests lobbied the US Government. GPS is now used for literally thousands of tasks including land surveying, asset tracking, vehicle navigation and aircraft position monitoring. it is yet to replace the barometric altimeter as the primary instrument for the vertical positioning of aircraft. In recent years GPS satellite signals have been augmented by ground stations such as WAAS and also recievers have increasingly sophisticated algorythms incorporated into device firmware such as DGPS and corrective strategies. This improvement of accuracy also makes my kite altitudes easily measured within 10 meters for altitude and 2 meters for position. This represents up to 0.004% accuracy for height and 0.001% accuracy for position when the kite is above 16,000 ft. The technical advances such as DGPS or Differential Global Positioning System and WAAS have even been added to the cheapest GPS recievers. Almost all of the telemetry units and hand held GPS recievers records data that can be displayed in maps and applications such as Google Earth. These units are relatively innexpensive. The cheapest Garmin units such as the etrex are only $A99. Originally the smaller unit, the Geko, had more memory and track points so could record a 10 hour flight. The cheaper unit, the etrex, had only enough internal memory for 3,000 track points. Frequently it would only record the last 4 hours of a flight cutting off the record of the first 1/3 of the flight. I have recently replaced these Garmin units with GPS data loggers like the HOLUX and the TripMate 852. Many consumer grade GPS devices focus on the position and often don't display altitude although the data is recorded by the device it requires external software to extract and display it. Almost all the devices comply with NMEA standards for positional data but often have proprietry methods of retrieval and display. There are a number of specialist programs that can read and convert virtually any GPS device's log files.
After the Garmin Geko was discontinued the new Garmin etrex gained the ability to store 10,000 track points so is now capable of 10 hour flight recording. The Garmin units are now only used to locate kites after line breaks when the last GPS cordinates recorded can be input to the hand held units. The GPS data is virtually uneditable unless you are a high level programmer so the GPS provides rock solid verification for record authorities. It is certainly many times better than the hiking watches used by Richard Synergy in his "record" flight of August 2000. Each of our GPS units has been checked by a registered surveyer against official bench marks and the degree of accuracy (or error) noted. The absolute accuracy of the GPS units is in the order of <20ft for position and <30 ft for altitude. As the altitude increases the percentage error gets smaller and small until it is almost inconsequential. Most of the time the accuracy is better than 10 ft for position and 20 ft for altitude. All GPS units measure altitude from AMSL or Above Mean Sea Level. Device specific software such as GPSFlight Dashboard a display both altitudes with the user inputting the ground level. Garmin Mapsource displays sea level altitude only and ground level must be deducted to give the kite's altitude AGL or Above Ground Level. This year we had 6 different GPS devices including GPSFlight Telemetry, HOLUX data logger, TripMate 852 data logger, BRB GPS telemetry, TLA GPS Telemetry and 3 garmin etrex units for ground searches. Of course we only use 2 on each flight and the other are backup units or ground search hand held units. Without GPS units we would need recording barometric altimeters. Early versions were used late 19th and early 20th centuries.
In 2005 we had an array of communicationn and tracking devices. L - R front: Motorola Walkie-talkie, 2 Garmen etrex GPS units, Garmin geko GPS unit, Titley Electronics 161 Mhz tracking transmitter. Rear: Alinco Scanner/Reciever and Yagi Directional Antenna. Some of these have been replaced by GPS telemetry and data loggers.
The early model Garmin etrex had limited track recording memory.
Late models have almost identical appearance but inherited more features from the Garmin Geko including larger memory for more track points.
Above: (L) is a GPSFlight radio telemetry module and (R) the RX3 base unit.
This model is a STXe 900 Mhz spread spectrum radio with Garmin 15H GPS module. It collects the GPS signal then relays the positional data back to the RX3 - base unit. The base unit connects via USB to a laptop and the data is displayed on proprietry software developed by GPSFlight. The altitude and position of the kite is displayed in real time which is an enormous benefit to our flight strategies.
Above is a horizontal kite track as produced by the GPSFlight telemetry unit and software. It shows the starting point on the right and how the kite may be subject to big wind direction changes as it climbs through the atmosphere.
Above is an altitude profile as displayed by the Garmin Mapsource program. The red dots represent track points where the garmin unit takes a positional snapshot. The interval is controlled to preserve battery life and memory. This data is transfered via serial cable to laptop to save and display.
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Garmin geko is smaller than etrex yet has a few more features, the most important is the ability to record 10,000 track points or over 10 hours of air time compaired to 3,000 points for the etrex.
These traces are produced by GPSFlight telemetry software, GPS Dash. On the left is the horizontal track and on the right, the vertical profile. Underlying these graphs are the data streams which can be produced in a number of formats, particularly valuable for record verification and also can be exported to MS Excel for display and graphical presentation.