Sailquik, that's interesting...... Maybe a separate issue, my Garmin always shows higher readouts on the display that what Realspeed calculates. Last night that difference was 1.7Knots ! Not insignificant .....it could well be what i am doing with my data, which is nothing other than uploading it, but if there is a better way to more accurately reflect what speeds I am actually achieving, then I am all for it.

wa881 said...

Sailquik, that's interesting...... Maybe a separate issue, my Garmin always shows higher readouts on the display that what Realspeed calculates. Last night that difference was 1.7Knots ! Not insignificant .....it could well be what i am doing with my data, which is nothing other than uploading it, but if there is a better way to more accurately reflect what speeds I am actually achieving, then I am all for it.

That will probably be because the screen readout is calculated on 1 second (Doppler) speed but the saved trackpoints are 2 second (at least they should be). It is a bit strange though because most people find the calculated speeds are often higher than the screen readout because of trackpoint grid effect error. It may be that your speed runs are orientated at a different heading. ie: along the 'grid' instead of across it.

nebbian said...
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.

Analysing data-errors isn't that hard for almost every corner case - the problem is that those "bad data rules" arn't yet available in the various programs. For example, I have quite a few tracks where RealSpeed and GPSResults incorrectly chose the wrong section of data -> some nice rules like "sailors cant turn 90deg. within 1 sec" would go a long way (ie: not a data "spike", but definitely a reality spike...).**

** That is not a criticism of the programs - just an observation on how they could be enhanced.

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?

This feature was added after first explaining that GPSSS already existed, but since GPSTC already some data regarding the sailor, so showing that page is pretty simple. The fact is that we cant "trust" any of the data as it relies on the user uploading their own values (eg: GPSSS had someone recently post a 47kn run on a slalom board... mistakes always happen). The trust factor that you are alluding to, wont be fixed by removing a fraction of a knot.

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.

That is an excellent idea. It states firmly that you are only cheating yourself.

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.

This is just my two cents here... as I saw it, people were being truthful according to the previously outlined "rules". The problem appeared to be the change of rules that some people inferred, as the year went on.

Aka, just like the addition of the individual-sailor page, where it was first stated that it wasn't accurate as it didn't undergo vetting, unlike GPSSS which has regional RTK's.

I guess some people are fairly competitive so its a valid concern to even things out, I'm a foretrex user and have absolutely no problem with a small reduction calculated by the site being applied if that brings the number closer to the "true" speed.
I'd get more value in upgrading my gear than tossing out a useable GPS just to post doppler.

25 said...

This is the thread we had to have!
It has overlapped and combined with the GTC 2009 thread.
Respect to Nebs for the courage to put it out.
It is true that whilst being a team based concept there is a serious individual side to it for many [me included] and this will not ever contract.
From where I sit this is an issue that needs to be sorted out so we don't get more of the sort of disagreement that led to a top sailor like Chris Dimond exiting the contest – please rejoin Chris!
My interpretation is that the consensus seems to be that the admin guru [Ben] should put in a mandatory option [check box] to declare which device and calculation method the poster is using.
As has been inferred by many, this would then make it obvious whether we are comparing an apple with an apple or a pineapple!
I reckon its a winner!

re check box's.