GPS And Vario Equipment For Competitions
How the logging and scoring works
Getting the information into your
GPS
MADE UP TURNPONTS (Manual entry).
Appendix I (MLR OS Grid crib sheet)
How the logging and
scoring works
Today competitions use GPS track logs, or other
recorded information from the GPS to verify that each competitor has flown the
set course. This system is very much more accurate that the photographs
previously used – both in terms of the organisers checking where the pilots
have been, and in terms of the pilots finding the turnpoint and progressing on
the course with minimum lost time.
The GPS records the pilots position at set intervals.
The turnpoints are defined waypoints that are downloaded into the competitors
GPS from the organisers computer (or entered manually – see later!).
To “score” he turnpoint the pilot must fly within a
set distance of the turnpoint (usually 400 metres) so that his track log passes
through the “cylinder”. Note that the track log is not just the track log
points, but also the straight line that joins them.
Note that you have got to fly in a way that puts your
track log into the cylinder (fig 1), turning too soon with a long track
interval will loose you the turnpoint (fig 2) but you can carry on through the
turnpoint straight and your track line will count (fig 3) Flying right round
the outside of the cylinder will not count either, even though you flew a lot
further than required!
fig
1
fig
2
fig
3
Getting the information into your GPS
Organisers will normally offer a download (squirt) of
all the waypoints into your GPS and often note your GPS serial number. They
also usually put a waypoint into your GPS that identifies you. At UK
competitions they also put in extra waypoints with the phone in numbers and
other details. Usually they will also give you a printed sheet with these
waypoints on, but photos are becoming rare!
The printed sheet should also have the MAP DATUM
(nearly always WGS84). There are many datums in the GPS and unless you set the
datum to the one on the sheet the lat and long or grid numbers in your GPS will
not match up. Even with them matched up there is sometimes a rounding error on
the last digit, don’t worry the last digit is one metre or less!
In the UK we might use OS grid datum and in the MLR
there are several OS grid datums (just one in the Garmin), the first one on the
list seems most accurate!
It makes no difference how your GPS is set when the
turnpoints are uploaded, the communication works with fixed points is space.
Changing the datum and coordinate type after the upload doesn’t move the
waypoint in the GPS, the displayed numbers will change to put the waypoint in
exactly the same position.
(On the MLR unit you might find that the organisers
program asks you to set the correct datum before the data transfer will work).
With the computer putting your waypoints into your GPS
it should be impossible to get the wrong waypoint positions.
MADE UP TURNPONTS (Manual entry).
Sometimes they make up a new waypoint for the task.
For this you must have the correct datum. ASK the organisers what the datum is
before you enter the numbers! Also beware of the difference between dd mm ss.s
and dd.dddddd and dd mm.mmm and UTM (the organiser needs to make this clear).
Organisers should not put different unit types (UTM, Lat and Long) on a task
board, they should stick to one format so there is no possibility of an
ambiguous turnpoint definition!
WHICH GPS?
When this system first came into use, the most popular
GPS in the free flying world was the Garmin 12 and 12XL. With approx 1000 track
log points the user sets this unit to record a position every 15 or 20 seconds
(see table) to give enough recording time for the competition flight.
A lot of competitions allow extra manually recorded
points (mark,enter) but on these units the “mark enter” is not secure – the
user can edit all the fields inside the unit and move the point to any desired
position. This has meant that often mark enter points on these units are not
allowed in major competitions (even though the capability for “cheating” is
minimal as the mark enter is surrounded by fixed track log points!).
GPS
units
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Garmin GPS 12 and 12XL For us there is no
difference between a 12 and a 12XL. The 12 doesn’t go beep (no
sound) and the 12XL has a bigger voltage range for external power – you can
plug it straight into a car battery. These are still the most
popular and widespread units so most experienced pilots will be able to help
you set it up and answer any questions you have. Fits most commercially
available pods. Avoid software 3.53 or
earlier as this means it cannot be upgraded as it has an old hardware build.
3.53 records a track log time 13 seconds late! |
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These are actually quite
hard to find (except in the USA). You can set the display
fields so you can see the time of day on the goto screen, but unfortunately
only to the minute not to the second (useful for the start). It has 2000
track log points. Its very similar to use to the 12 and 12xl. You can load a reasonably
detailed map of quite a large area from the (expensive) mapsource CD (not the
clutter seen here!) but not any airspace inf. Same size as the 12 so fits
most commercially available pods. |
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The Garmin GPSIII has been less popular due its odd
shape and vulnerable external antenna. The screens and software are almost
exactly like the 12MAP Won’t fit any commercially available pods due to it
odd shape. |
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Garmin “route” headaches.
When you program the course as a route on most Garmin
units, circling close the waypoint, or crossing the next part of courseline on
the way to the turnpoint, tends to make the unit switch automatically to the
next turnpoint. This is very frustrating! Often if you circle before the
turnpoint you end up doing a lot of button pressing! It can happen very close
to the turnpoint just when you really need the information and leave you
guessing (very dangerous in terms of loosing your score) or wasting time in sink
pressing GPS buttons. Many pilots do not have the route active but just use the
route listing to quick access the next waypoint for a stand alone goto.
To do this, enter the task as a route (any number
except 0 on the 12!). Only store this one route, delete the previous day. If
you list this route while flying you can scroll though it to the waypoint you
want and hit goto, enter. This saves scrolling through possibly 100’s of
waypoints looking for the right one. As the route is not active you have to do this
every turnpoint, but it will not switch prematurely.
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MLR’s SP24XC Vol Libre (or free flight) version now has 8000 track log
points including altitude. However the track interval can only be set to 1 second
(a bit too short) or 5 seconds (gives ages!). The MLRs advantage over most Garmins is that the route system on the
Vol Libre will not switch prematurely. You set the waypoint alarm distance to
a little less than the cylinder size and the unit will not switch to the next
waypoint on the route until it has recorded a track log point in sector. (see
Garmin route headaches) Also by programming waypoints in the right format, where the last
three characters indicate the altitude, you also get a glide angle indication
to your next waypoint (GR: bottom right of the compass). Note you also get to
see the time to the second on the goto screen - great for the race start. However the menu system seems more difficult to follow than the Garmin
(but most of us “grew up” with the Garmin!) and if you want to use the
British Grid system you need to look up the numbers that represent the
lettered zones like SK, SJ etc (they are on the edge of the OS maps on the
edge of each area) This makes it hard to enter a point that someone else has
on their Garmin without a bit of maths (or swapping to Lat and Long). Same size as the Garmin 12 so fits most commercially available pods. |
NEW GAMINS
WARNING – A lot of the lower priced new etrex range only have an automatic track log – you cannot set the track interval and after only about 1.5 hours it starts to remove points from the beginning of the trace for reuse! Make sure you buy the correct model!
Garmin now offer a special download for their new 76
and etrex vista units which cover most of the features previously unique to the
MLR. Unfortunately they are too commercially astute to offer these features as
an upgrade to the 12!
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These small units run for ages on two AA
batteries and will clearly take over from the 12 type units. Track log records altitude. The ventura
is the cheapest model that offers capability to set the track log interval. Operation requires access to buttons on
the side of the unit so mounting in a pod will be difficult. However the
small size means they are potentially more aerodynamic. |
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With the Vista you get a built in
electronic compass and the track log records altitude (like the MLR). Garmin have just released a new update
that gives glide angle, required glide angle to waypoint, and, at long last,
a way to make the route switch manually (not automatically). On the compass
screen you also get an indication of the direction to the next waypoint on
the route as you approach the current one (that’s a new idea!). |
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The 76 also has the improved functionality on the latest download
including the manual route waypoint switching. This is a bigger unit with a
larger display, just slightly wider than the 12 but thinner. |
DATA LOGGERS
One simple way to get round the shortcomings of an
older Garmin is to plug it into a datalogger. Then you will get hours and hours
of track log with thousands of points, usually including altitude.
Some varios will also double as dataloggers.
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The Log-it is a simple way to keep up in the GPS race. Simply plug one
of these into your GPS and provided your GPS keeps coverage then it will log
a point every 2 seconds for over 18 hours! Thankfully it will also download to the computer at high speed or
you’d be in the scoring room for hours! |
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Digifly’s explanation of how their logging system works. You set a
radius from the waypoint at which you want the fast logging to start, and enter
the radius of the cylinder (or a slightly smaller radius to be sure). Normally
you set the logging to anywhere between 3 and 15 seconds, but when you are
inside your “near” zone it logs per second (displaying NEAR). Once the unit
logged three points inside your set cylinder it gives you the WPOK (waypoint OK
display), it switches back to the normal track interval and you know you are OK
to carry on.
Furthermore the GPS reads the waypoint from the GPS and has its own
display to navigate toward it. Should the GPS switch to the next waypoint
before the Graviter has logged it as valid then the vario warns you and enables
you to navigate the original waypoint without resetting the GPS. (ie you can
have the GPS pointing toward the next waypoint on the way to the first one
after the Graviter has memorised the first waypoint). So this instrument has
cures for most of the “Garmin route headaches” and seems to match the best of
systems even when connected to the most basic of GPSs (you could use it with
the cheapest etrex for example and have a really small instrument combination–
smaller then a Gallilleo)
The digifly also includes an electronic compass (if the instrument is
laid flat) and a direction finder telling you which way to point to get to the
waypoint (taking account of the wind).
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The Renchler Sol unit now has data logging in its latest GPS access
software. |
Combined GPS/Varios
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The top navigator was perhaps the first instrument to take GPS logging
seriously with its internal GPS recording 4000 points including altitude.
Note that to use the unit for competition you need the year 2000 software
upgrade! Very popular in paragliding it’s a rare sight in hang gliding due to
its brick like bulk. There are many graphical features to do with thermal tracking that the
owners think are really cool! |
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The Brauniger Galilleo is fresh out this year. Lots of track log
points and a whole new system to learn. I don’t know much about it yet, but
expect the wind and glide to goal calculations to be much better than the IQ
comp due to the increased data transfer rate from the GPS. Also the ASI is
pitot static so there are no moving parts. One nice feature for us Hang
Glider pilots is that you can set the sound to get louder with increasing
airspeed so at least all the development isn’t for the paragliders! With this instrument new this season there have been some PC
communication issues. Also check on the FAI status for the barograph before rushing to
Zapata with one! |
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INSTRUMENT |
Number of track log points |
Hours at 20 sec |
Suggested track interval |
Hours at suggested interval |
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Garmin
38/45**** |
500 |
02:46:40 |
30.00 |
4:10:00 |
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Garmin
12/12XL |
1024 |
05:41:20 |
20.00 |
5:41:20 |
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Garmin
12MAP |
1900 |
10:33:20 |
10.00 |
5:16:40 |
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eTrex
Venture & Legend |
2048 |
11:22:40 |
10.00 |
5:41:20 |
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eTrex
Vista |
3000 |
16:40:00 |
7.00 |
5:50:00 |
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Garmin
MAP 76 |
3000 |
16:40:00 |
7.00 |
5:50:00 |
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MLR
SP24XC Vol Libre |
8000 |
20:26:40 |
5.00 |
11:06:40 |
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Logit*
+ compatable GPS unit |
32752 |
n/a |
2.00 |
18:11:44 |
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Digifly
Graviter** + compatable GPS unit |
10000 |
07:33:20 |
3.00 |
8:20:00 |
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Top
Navigator** |
4000 |
22:13:20 |
4.00 |
6:40:00 |
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Brauniger
Gallilleo*** |
10000 |
07:33:20 |
3.00 |
8:20:00 |
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Renschler
SOL with integreted datalogger** |
40000 |
n/a |
1.00 |
11:06:40 |
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*Data-logger |
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**combiner
Data-logger/Vario |
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***
combined Vario/GPS ****These
old selective channel units will loose coverage often – upgrade to a 12
channel! |
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Instrument mounts
Its nice to have all your clocks in one lump to put on
the glider without a tangle of wires. These things cost of the order of £100 and
are difficult to get hold of. Most of the commercial mounts are not that good
and the pod usually needs a nose wire attachment to stop it swinging about. One
way is to fix a bolt right through the upright!
Brauniger pod –
variations from Aeros and Lamoutte
Betinho’s pod from Brazil. There’s a circular plate on the back with a
central screw allowing the pod to swing up out of the way. Mike Stephens and
~honest TJ have this one.
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Flytec’s
pod is hollow to house the GPS76 and others. The ASI is ducted inside. |
Air
Blade pod by Valerio Canestrelli vacanes@tin.it Someone’s
always got something more expensive and flashier! |
Appendix I
Use this table to determine the Northing and Easting numbers from the OS
Grid letters if you have an MLR or another GPS that won’t display or enter the
grid letters.
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12 |
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HP |
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11 |
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HT |
HU |
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10 |
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HY |
HZ |
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9 |
NA |
NB |
NC |
ND |
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8 |
NF |
NG |
NH |
NJ |
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7 |
NL |
NM |
NN |
NO |
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6 |
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NR |
NS |
NT |
NU |
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5 |
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NW |
NX |
NY |
NZ |
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4 |
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SC |
SD |
SE |
TA |
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3 |
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SH |
SJ |
SK |
TF |
TG |
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2 |
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SM |
SN |
SO |
SP |
TL |
TM |
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1 |
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SR |
SS |
ST |
SU |
TQ |
TR |
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0 |
SV |
SW |
SX |
SY |
SZ |
TV |
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0 |
1 |
2 |
3 |
4 |
5 |
6 |
Appendix 2
Some Garmin 12 software has an error which makes the time in the track
log out of step, running slow by about 13 seconds. If you are buying a 12 or
12XL make sure it runs software 4.0 or newer, and then update the software to
the ltest available by downloading from http://www.garmin.com