jeff3069

Dear All,

Can anyone explain exactly how TDF gap is calculated ?

Thanks!
J

Caretaker

Don't know how they do it exactly but something to do with transponders on the bikes that show the time difference between the lead group/rider and the yellow jersey. In the TdF usually reliable, in other races not always so.

It's the time it takes the following rider to reach the same point on the road that rider number one has already passed.

Beach Bob

In this morning's broadcast, right near the end, they were having all kinds of problems with the gap and were getting it from race radio. From what the commentators were describing, it sounds like it is normally calculated from the motorcycles riding with each group. Sounded odd, but they attributed the wonkiness to one of the motos stopping.....

jeff3069

********

Thanks guys, though the question is How. using the speed and coordinates of the pursuer, the speed and coordinates of the leader, the distance and specific pattern of the road between them (slopes/corners...)

brianmcg123

prathmann

Can't say how 'they' do it, but I would look at the current position of the pursuer and check the time when the leader was at that same position. Then subtract that time from the current time to get the gap.

slcbob

**********??

It's one of two things.....

Someone with a stopwatch times the groups go by. Old school, and they still do it at times, particularly for the gaps that are put on the chalk board of the yellow LCL bike.

GPS based. Typically they are comparing a beacon in the current bunch to the time a beacon (maybe on a moto or commissar car, more and more from the bikes) in the prior bunch went past the same point, but there are various data providers and different races and lots of methods. My exposure to it is barely scratches the surface, but to my knowledge none of the legit ones do any dead reckoning or estimating forward, they are back-checking.

colombo357

It's just elapsed time using virtual "checkpoints" based on GPS coordinates from the transponders mounted to the bikes.

Rider A passes coordinates X latitude and Y longitude at 10:30:00
Rider B passes the same coordinates at 10:33:30

Rider A is 0:03:30 ahead.

jeff3069

So there's an assumption that they move at the same speed. this is wrong. a closing peloton sometimes move Faster than the break (just an example) - if TDF want something near accurate they need to take speed differences into consideration

colombo357

Meh, the gap is constantly updated to take speed differences into a count. That's why you often see breakaway gaps plummet.

slcbob

No, Colombo is on it.

It is a simple historical gap, not some sort of complex pro forma thing.

Every once in a while Paul Sherwen will refer to the computer estimate of when the break will get caught. You can go all Alan Turing on that gonculator, but not the gap timer.

dstrong 

Along the same lines...the graphic that drives me crazy and seems completely useless to display is when they show the speed of the breakaway and compare it to the speed of the peloton...when the break could be going uphill and the peloton could be going down!