Competition GPS Users Guide

This article can be read at
http://www2.eis.net.au/~tim/classic98/gpsguide.html

Canungra Classic Trials GPS Verification

The 1998 Canungra Classic has been given approval from the HGFA Competitions Committee to trial the use of GPS Track Logs for turnpoint and start gate verification and timing. To aid pilots flying in this years Classic, I have prepared this Competition GPS Users Guide. My experience is that GPS Verification is much simpler for the pilot than Photo Verification and I would recommend that all pilots obtain a GPS for this competition. If you do not have a GPS you will not be disadvantaged as photo verification will still be an option. As this is a trial, all pilots are recommended to carry at least one camera as backup for the GPS. Our trials to date have been with Garmin GPS. Users of other GPS makes will need to provide their own software for downloading the track data.

1998 Canungra Classic will be trialling GPS Turnpoint Verification Entry fee only $100 ( + site fees $35).

GPS Initial Setup

All GPSs should be set with the following parameters
Time Zone: GMT +10:00
Datum: Australian Geodetic 1966
Track Log Interval: At most 30 seconds
Track Log Duration: At least 6 hours log.
Waypoint: Name = PILOT, Comment = Pilot's No + Name

On a Garmin GPS the following screens show where this data is set.

OPERATION SETUP        NAVIGATION SETUP       TRACK LOG SETUP        
------------------     ------------------     ------------------     
MODE:                  POSITION FORMAT:       RECORD TRACK: Yes      
 Normal                 UTM/UPS               ------------------     
------------------     ------------------     CRITERIA:              
DATE  -- --- --        MAP DATUM:              Time Interval:        
TIME   --:--:--         Astrln Geod '66         00:00:30             
OFFSET: +10:00         ------------------     ------------------     
------------------     CDI Scale: --.--       MEMORY USED ---%                    
CONTRAST               ------------------     --- OF 768 POINTS                   
 --------              UNITS: Metric          ------------------                 
------------------     ------------------     CLEAR TRACK LOG?                    
BACKLIGHT TIME:        HEADING:               
 -- seconds             True                  
TONE:---


I/O SETUP              WAYPOINT
------------           ------------------     
GRMN/GRMN              NAME:PILOT         <-- important
 HOST                   -- - -------      
 WAITING...             UTM  -------      
                        65 TIM CUMMINGS   <-- your number and name here
 __ OF __              ------------------     
 PACKETS                REF:______
                        BEARING DISTANCE
                         000°     0.00km
                       ------------------     
                       RENAME?
                       DELETE?    DONE?

That is all there is to it. These settings can be set well before the start of the competition. Why not set them now! There is no advantage to the pilot to have different settings as the computer software will compensate. However, data could be lost if they are not set.

GPS Operation

There is a requirement that the track log includes 10 minutes (or total flying time if less) BEFORE and 10 minutes AFTER each turnpoint or start gate. It is also a requirement that at least 30 minutes of track log per flight is recorded. To verify a turn point or start gate at least part of a track log segment must be inside that turn point or start gate sector. ( A track log segment is the straight line between two consecutive track log points less than 60 seconds apart) As an added security to ensure the GPS records an "in sector" segment, the pilot can mark a waypoint while he is in sector. If the timestamp on this waypoint is consistent with the automatic track log it will be considered as a track log point.

The simple steps to achieve these requirements with a Garmin GPS are:

BEFORE Launching - Turn GPS on
While In Start Gate Sector - Press MARK then ENTER
While In Turnpoint Sector - Press MARK then ENTER
AFTER Landing - Turn GPS off

Pressing MARK then ENTER records a waypoint which will be added to the Track Log. This is optional but highly recommended where the course line deviates significantly around the turnpoint, for example in an Out and Return. To ensure an accurate timestamp make sure you press ENTER within 5 seconds of pressing MARK. You can add as many waypoints to the Track Log as you like. If you were not sure your first one was in sector, then when you are sure you are in sector, press MARK then ENTER again.
Pilots using GPS logging with more frequent data points, say every 5 seconds need not be concerned with manually setting waypoints. They can just fly the course. Sounds perfect doesn't it!
You don't need to have the GPS on the whole flight but remember it needs to be on for at least 10 minutes before and 10 minutes after each turnpoint. Also, if a GPS doesn't have a fix it will not be recording track log entries even if it is on. You don't want to be circling at a turnpoint waiting for your GPS to get a fix. Of course, to leave your GPS on all the time you need good batteries.

It is strongly recommended to use 1000mAh or better AA batteries in Garmin GPSs.

FAI Sectors

Turnpoint

The FAI Sporting Code Section 7 (6.6.8) states that:

"The photo sector is a quadrant (90 degree sector) on the ground with its apex at the turn point and orientated symmetrically to and remote from the two legs of the course which meet at the turn point."

Furthermore the HGFA competitions manual 3rd ed (2.8.2.1) states that:

"The sector limit is one kilometre from the quadrant apex."

For the purposes of GPS Verification, the area of the sector has been increased to allow for 100m random error (Selective Availability) of GPS devices.

"The area within 100 metres horizontally from the turnpoint is considered part of the sector"

The Beer Can turn point sector as it is often called looks like the following figure. GPS Turnpoint Figure

Start Gate

The Start Gate also includes the 100m radius around the Start Point, as is shown in the following figure. Advantages in using GPS Track Log for a Start Gate are that all GPS tell the same time and from the Track Log the time that the glider crosses the start line can be interpolated to the nearest second.

Goal

The HGFA comps committee has requested that traditional means be used for determining goal crossing times. At the Canungra Classsic we will also calculate the crossing time based on the GPS as a double check and also to evaluate the feasibility of using it in future competitions.

Examples of Track Log Verification

Full List of Rules

Some special rules have been developed by the HGFA Competitions Committee for use of GPS at Canungra. For a full list of rules see http://www2.eis.net.au/~tim/classic98/gpsrules.html.

Conclusion

The Canungra Classic this year promises to be an ideal competition for pilots new to competition flying intimidated by the complications caused by cameras. The entry fee has been reduced THIS YEAR ONLY to encourage newcomers to enter and fly with Australia's best. See the Skysailor Competitions Calendar for details or check out http://www2.eis.net.au/~tim/classic98/classic.html and enter online!.
The use of GPS in hang gliding and paragliding is a welcome addition that removes some of the major hurdles to successful and enjoyable competition flying. The potential of this technology is only just starting to be realised and I am sure there are many novel applications of the technology still to be devised.

Last Update 28 June 1998