Zezo forum: Estimated Record Time on a record race

Estimated Record Time on a record race

Post by Paspox | 2021-06-21 | 08:02:05

Can someone explain to me how it is calculated ?
I'm assuming that the VR dashboard knows the time already spent on a record attempt (from the start to your position : t1).
It then does a routing from your actual position to the finish which gives a new time (from your position to the finish : t2) and ERT = t1 + t2
Is that how it is done ?

7 Comments

Post by Paspox | 2021-06-21 | 08:08:56

I read somewhere that the way it's done is different.
VR dashboard knows the time already spent on an attempt (t1) and the distance you've covered (d1).
It calculates your average speed so far (v1=d1/t1).
It knows the orthodromic distance to the finish (d2), assumes that you will be as fast as before (which is quite an assumption!) and calculate the time remaining (t2=d2/v1).
And ERT = t1 + t2
This way, there is no routing necessary but it is much less accurate.

Post by Paspox | 2021-06-21 | 10:18:32

Oops ... should have checked the user manual before posting !
It says :
ERT
Estimated race time. Only in record races.
VRDashboard estimates the overall race time based on the average speed achieved since the start. It uses the elapsed time, distance from start and distance to finish provided in the VR server 'UserCard' message.

Post by BooBill | 2021-06-21 | 11:04:47

The ERT estimate in dashboard can be really misleading. Two boats that started together and are now side by side can have different ERTs if they took different paths to get there. The one that sailed a longer course will have a higher avg speed and therefore show a lower ERT. And, as said above, it assumes you sail a direct ortho to the finish at your avg speed so far.

The only way to get an accurate answer is to run a routing to get an estimated finish time and then do the date/time math.

Post by Paspox | 2021-06-21 | 15:56:16

Thanks.
Based on how it is calculated, I was wondering how useful the ERT really is ... and I guess the answer is : not that much !

I did what you suggested to get an accurate answer for the Atlantic record : I'll arrive 24h later than what the ERT is saying :(

Post by Stevoo | 2021-07-07 | 06:09:01

The ERT is based on your current average speed, which will never be accurate to the finish. The only way to calculate is your elapsed time, plus zezo time to finish (if you have a solution to the finish)
VR used to post your elapsed time in the boat pop-up, but that useful option is gone.
i use the following to get elapsed time
https://www.timeanddate.com/date/duration.html

Post by BooBill | 2021-06-21 | 23:39:41

Yeah, the low we are riding peters out and then we have a high pressure ridge to go over in the day before the finish. I think the guys further north have a better chance.

Post by Paspox | 2021-06-22 | 08:55:19

You are right. Boats way north that have left just a couple hours before me will arrive a good 20h before me !
The ones I've checked are better equipped than me but still, further north does look better..