A couple of people have asked me whether we're using trackpoints or doppler for the challenge this year.
Personally I'm using doppler as it's less mucking around when you get the file, whereas trackpoints tend to give you a slightly higher reading.
Is GPS-SS using doppler only this year?
What are other people's thoughts on this?
Since I've gotten the Navi 2 months ago I've been using Doppler, it's a lot easier to work with.
I don't have a problem with others using trackpoints if that is what they want to use or have to based on the GPS they use.
At the end of the day this is still for fun, an excuse for a sail and bragging rights
Basicly GPS-SS are saying that is you have a navi gps you should be posting doppler. I think we should stick trackpoints for now and see what happends with
GPS-SS.
It seems ridiculous to me to be running a competition and people using two seperatre forms of measurement??? With one consistently showing lower speeds(Doppler) and one consistently higher speeds (track Points)
Track points should be used as there are sailors with only garmin's and we could ask everyone to have a NAVI for 2009.
..........and Yes as Vando said see what GPS-ss decide after trialling doppler for a year.
But it's not the end of the world if we use 2 seperate measurements, hope no-one has bet a sheep station on any of the outcomes here, after all it's more about the fun, competing and relationship building. However, I do reiterate, to use 2 separate measurement systems seems ridiculous to me!!
There are two main reasons the GPS-SS guys are going over to Doppler. The first is that it is more consistent. This is better for high end competitions and rankings where the results may be only separated by less than 0.1 of a knot. (Trackpoints from Foretrex and Geko in side by side test can, and have varied significantly more than this. The variation between trackpoint speeds for side by side GT-11 is smaller but still significant).
This means that the range of speed from side by side GPS are smaller using Doppler.
The second is that with this smaller range of deviation it is possible to use a system of claimed speed. This is a step towards making GPS speeds more officially acceptable (just one step towards I must emphasize). This means that the error that can be calculated from statistical analysis can be deducted off the speeds so one can say they have done at least the speed claimed with 98% or 99% probability. Note that this has no effect on the rankings of comparable GPS devices and is only aimed at comparing with official speeds. Theoretically, it also allows the same rules to apply to different GPS devices. For example, if you use a Garmin Foretrex or Geko it is possible to deduct an amount off it as well to make a claimed speed 99% probable. The fly in the ointment here is that the deduction for Garmins (and other non Doppler units) is probabaly going to be so high that the users will spit the dummy and go play with model trains or something.
There is a lot of statistical analysis going on at the moment in the background by a highly respected GPS-SS member in Europe to try to refine the claimed speed deductions but there are still a lot of decisions to be made about it and it is unlikely to be implemented completely in GPS-SS for some time.
In the meantime, I suggest we continue to use trackpoints for this year and see how the GPS-SS situation unfolds. Since ours is very much a fun ranking and mainly a team event anyhow, the results are a bit more accurate because they are always an average of two members. (the more samples you use, the less error there is.)
Also it must be noted that even within GT-11 devices the difference between Trackpoint speeds and Doppler speeds can be quite significant. EG, for my session on Thursday it took my 5 x 10 sec speed from 41.7 knots down to 40.9 for Doppler. Other riders reported similar differences. So I would say to those guys posting Doppler results in the Team challenge, take note of how much you are taking a hit on your speeds.
I have found that when using GPS Results and RealSpeed to do the analysis, there is very little difference in the ease of getting results from Doppler or Trackpoint. Most of the time the results need no further adjustment either way if you have a reasonably clean track.
I think education and maybe a tick box showing if you used Doppler.
Then the Doppler results could be displayed in black and track points in blue or something like that.
So a combined doppler would be black and a doppler +track point in blue.
You are not penalising anyone and just showing a difference.
I have only used the Doppler results but I had very good guides to set-up the NAVi
My 2c
GPS-SS also verifies tracks. Not one track in this challenge has been checked, or at least very few.
Keep it simple, if doppler floats ya boat use it.
Sorry Nebbian. To answer your original question. GPS-SS are allowing posts from Non Doppler devices this year and are intending to have a 'star rating' system to show the reliability level of the postings. It is quite possible there will also be a token (statistically derived) deduction for non Doppler devices to even the ground out a bit. There is talk about possibly going to the full 'claimed speed' on all devices for 2009. All the riders in the top 20 or so are expected to post Doppler. Their difficulty is the huge user base that still use non Doppler devices who don't really have much interest in the finer points of high end competition and accuracy so they are trying to find a way to be as inclusive as possible but cater for the serious speedies as well.
As a comparison between the two formats check Slowies post from GPSSS where he puts all the different results between what he posted Navi/ Doppler, Navi/TP and Garmin/TP
www.gps-speedsurfing.com/default.aspx?mnu=user&val=26124&uid=203
There is considerable differences in the results.
At the end of the day the use of Doppler handicaps only the person who uses it and does not affect others.
If trackpoints is still accepted and Doppler and option, then if a person chooses to use doppler it is their prerogative as it is only themselves which they handicap without impacting on others with older GPS's which have no choice in the matter.
Myself I will be sticking with Doppler, it is a lot easier to work with
I've just seen this debate from a different perspective.
So far it's all been about the individual.
But this is a team challenge.
Shouldn't it be the right of the team captain, to ask that trackpoint data be posted, if he/she thinks their team is being unfairly disadvantaged by members posting in doppler. (Especially if said member is the fastest in the team).
The members can always paste the doppler results into the comments section.
