I need some technical advice here.
In 2008 we had a situation where some people posted in doppler, while others used trackpoints.
This led to problems...
I requested tracks from various people on a semi-random basis, and without fail, every time there was a problem, it was when that person was using trackpoint data. The issue I have is that many people aren't all that experienced at figuring out which points are valid, and which are spikes. And spikes seem to happen far more to trackpoint data than doppler.
Garmins also played a large part in the problems we had with people claiming a speed that we didn't agree with.
So for 2009, I'd like to level the playing field somewhat. I don't want people to feel that they are being disadvantaged by using doppler... so I want to implement the 'claimed speed' that Manfred Fu chs and others on the GPS-SS site have been talking about.
This is quite easy to do from a technical perspective, just put in some 'fudge factors' for the various divisions, which relates to the type of GPS you're currently using. So if you use a garmin then the fudge factor for the 2 second speed might be -1.5, or if it's doppler on a GT-31 it might be -0.05 (or something, I don't know the exact numbers!).
I can implement this so that it's really easy to see, most people probably won't notice. And it should make the competition fairer, and hopefully avoid the temptation to use garmin data when NAVI data is available. I don't want anyone to feel like leaving the challenge 
How does everyone feel about this? Technically, what numbers should I use? Would this system discourage people from posting?
No drama's here, so we nominate the gps we are using?
It should never have been a problem to begin with, you are only lying to yourself... if you've done claimed speed once then you can do it again.
Maybe one of the gps guru's can post a sticky thread/tutorial on reviewing data and how to spot/treat spikes and also reviewing alphas.
But at the end of the day each user should have a general idea of gee this is faster than i've ever been before, i've see some valid looking tracks but you just know it was incorrect (including one of my own from the old garmin).
Nebbs, do all the software programs give claim speeds?
i am using gpspro, i am not sure if it has this feature?
What is the science here?
Doppler gives higher speeds for NM and 1 hr, and I think distance?
Is there going to be an adjustment for these as well?
We need to be careful here.
One thing though how can guaranty that the Software is setup the same for each person.
Perhaps we need a default rsp file for realspeed that everyone uses for this challenge im not sure if those settings are in the rsp file though.
maybe Timemachine can answer this.
ta Vando
I think you are right on the money here Nebs; we need to make it an even playing field, while at the same time allowing Garmin users to be a part of it so that we have the maximum number of participants.
I assume we would just be selecting an option for which GPS we are using and the system would do the rest?
It's just a matter of getting the adjustments right.
To clarify how this would work:
When inputting data, you still type exactly the same numbers as you would have done so before, but you also select which GPS (and trackpoint/doppler) you used.
The website would then adjust your scores according to the type and accuracy of the GPS that you have selected.
Sounds simple enough Nebs. as long as it is user friendly for eveyone it can only benefit the challenge.
Dont think it will help me in my quest the catch the red furry muppet though
Personally, I'd leave it as is.
It is to hard and complex to calculate an accurate "Fudge factor".
If you eliminate old GPS's then some people may not want to or afford to bother replacing them.
If you want have a box to tick as to what equipment you are using.
As Hardie said Trackpoints only comes out better for the small distances the larger ones give better on doppler.
I would have a clause about mixing TP and Dop for the one session (Alpha excluded) in case there are some real sad cases out there (not saying there are mind you) who run both so as pick and chose between settings.
Still yet to see the cattle stations on the prize list.
A levelish playing field is good enough if we are not to uptight about it.
If people demand more there is allways GPSSS or organised events.
This is suposedly all done for Fun.
KISS
Some observations:
The GT31 with the latest firmware from Tom's site (www.mtbest.net) gives very small differences between trackpoint and doppler results. I have not had either of my Navis lock up since updating a few months ago. With the GT11, trackpoints almost always read higher. The most consistent results come from the doppler data of the GT31. The GT11 doppler data is also more consistent than its trackpoint data. Thats why doppler should be used if available. It helps keep the ranking clean.
By consistency, I mean the agreement between units exposed to the same conditions (eg worn at the same time). Thats what you need for a fair ranking. Manfred has done some great work compiling a lot of data to get some reasonable statistics on the consistency of devices, and differences between device types.
The only downside to this is that the guys with lower quality GPSs (eg garmin) will be scored with lower than their actual speeds more of the time. Whereas someone with a navi would have scores much closer (and therefore higher). So using a Navi would almost always (depending on confidence level selected) give you a better corrected score than a garmin worn on the very same arm at the same time. This is a result of applying a correction to meet a certain level of statistical confidence that the "corrected" speed is at or below the actual speed- with the correction based on collected statistics for that GPS type.
Unfortunately theres no way arround the lower resolution of the garmin. It sometimes reads a few knots higher, and sometimes lower. Same with the Navi, but not as often and not by as much.
So this begs a few questions:
1) will it make a big enough difference for anyone to care about? How serious are we, really? Do we care about a bit of noise/uncertainty in the ranking?
2) how much confidence would we need that the corrected speeds are at or below the actual speed? The more confidence we need, the bigger the penalty on garmin users.
3) will having a correction put off the garmin users, when they see their 2 sec speeds get slashed by a lot?
Technically its a sound idea, but practically theres a risk of losing some of our garmin users if they get upset at their 2 sec peak speeds being hacked. The other categories would be significantly less tweaked.
I think its a good idea if the garmin users endorse it- after all, they are the ones who would be most affected, and I dont think any of them are choosing garmins for the inflated peak speeds
What will be the fudge factor for my older GPS. It's a GT-001 Chip Log my grandfather gave to me
I'm finding it really hard to download the log-line data to my commodore 64 and keeping the sand from getting wet in the hour glass also - I suppose it could go in an aquapac.
i think that if your going to put those inputs for board type, sail type, height, weight etc. the list goes on. just put one of the inputs as what GPS your using, then people will know how valid the data is. i think you can rely on those using Navi's to use the doppler as that is most accurate anyway.
Bubs
I just can't seem to get it to do the things I want it to do in the user interface, apart from just getting a simple result. I don't know if GPSAR Pro has the facility to display 'claimed speeds' as I haven't used it much for quite a while.
Sorry wrong threadSince it is a Team Challenge, what about awarding bonus points if any team can get all their members to sail any given day. Points could be graded i.e. a team with more members gets more points deducted from their overall monthly standing. Say each member is worth 0.5 of a point so a 10 person team could effectively knock 5 points off their tally - I am unsure whether this is too much or if my idea is just plain stupid.
I think where it could get interesting is towards end of month where one team is 3 points behind another but organises all the team to sail a given day (maybe a minimum distance per member is set for it to count)
. Also, it must be a bit of a pain winding it all up at the end of each run!
Now correct me if im wrong, but the only category with a signifigant difference (usually) between garmin and gt-xx speeds tends to be the 2sec?
So why not just get garmin users to post max display instead of trackpoint 2sec?
This is what I've done with all recent (fast) sessions, and it seems to be a lot more accurate than software 2sec- on the fewtimes ive had a chance to compare to the navi doppler the speeds were (from memory)
garmin 39.5disp 40.2 2sec, navi 39.4 doppler
garmin 36.5disp 37.5 2sec navi 35.99 doppler
Nebs,my vote is to keep it the same with no adjustment. As we take an average of two sailors to get a speed any difference is haved.(Does that make scence) Lets keep posting in track points with all its problems,then were comparing apples with apples. If people want the absolute speeds then post to GPSSS as well,but people shouldn,t compare the 2 sites as they are different totaly comps. As to spikes in tracks ,a thread or article written to help all people through the various programs on how to get the right info out of your gps would be great as not every has a Daffy or Matt to help. I like that anyone can post with any GPS, we need more people sailing and having fun.
I'll vote to keep as is, I don't really care who posts TP or D although I always post Doppler myself, as I just want the most accurate data.
Maybe post brand & model GPS, and weather it's TP or D with each session, some box's to tick 
Hey I'm glad this thread is up because i was going to ask a very related question.
Being new to GTC i am using Garmin 201 and i have noticed that my 2sec peaks in realspeed are ALWAYS lower than my peak speed readout on the Garmin. For example today i peaked at 30.7 on the garmin but only 29.04 on my 2 sec peak. that just doesn't seem right.
so do i assume correctly that there appears to be a 'lowside' error with garmin when posting numbers to realspeed?. if so, i would like to see some simple form of adjustment or i'll have to buy a navi, because it is frustrating me big time when i go and sail what i think is a fast session next to others to then see much lower peaks compared to others posts (that's not to say that i should be going faster than others, just that some thing doesn't smell right in the numbers)
The screen display on the Garmins never matches the computer.
I use the numbers from the computer because the display speed could be a spike.
When looking at the numbers on the computer you can see if there is a spike & disregard the speed.
For the 2009 competition couldn't everyone post in Trackpoint, assuming GT11/31 units have that option or a setting change in the program.
Surely you can still look at the Doppler for personal reference while polishing your fin
When everyone has eventually changed to Navi (say 2010 season) then change to Doppler only.
Hi Paul,
The problem with people using trackpoints is that most people don't know what a spike looks like.
They load up their file, type in 6 numbers and a quick story and hit submit.
If you are experienced in data analysis then this isn't an issue, but most people aren't experienced (and sometimes don't even click on each value to see what it looks like on the map display).
This is why I would prefer that everyone use doppler (or be penalised for using trackpoints). You don't have to be a rocket scientist to figure out how fast you went if you use doppler.
Some people wrote above that the team aspect will average out any high scores, but this doesn't take into account the personal rankings -- which some people put a lot of weight on. What use is a personal ranking page if you can't trust the data that's on it?
I guess the general consensus is that we shouldn't change the numbers that people submit, but we should put in an option to say which device and calculation method the person is using. This would then make it obvious how much faith we can put on that number.
I would also like to put something in the rules to say that you "enter the speed that you think is correct". If you choose to use claimed speed, doppler or trackpoint, then that's up to you.
It might seem to some people that I'm being overly pedantic, but people really do take this thing seriously, and if we can get the rules correct then we hopefully won't have another fiasco like as happened this year where someone decided to leave the challenge. I really don't want that to happen again.
so Nebbs, are you saying that the Garmin will always give 'slower' results especially for the 2 sec peak ? because that is the conclusion that I am coming to.....is that because it only smaples every 2 secs? Does the Navi do it more regularly?.
I am assuming that the Garmin 201 uses trackpoints ?.
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