GPS - TT v6 Road Speeds.

Author

TT v6 Road Speeds.

Rick

2006-09-19, 10:33 pm

Having just installed the very latest M.O.W.E. on my 700, i now see that the
speed now also shows the actual speed of the road as it is now supossed to
on this software/map release.

What i find amusing is that yet again, the Isle Of Wight has not got any
road speeds according to TT. Although i have not yet travelled all over the
island using 700 the roads i have been on do not show the road speed.
This is exactly the same with the TT cameras. There aren't any according to
them, yet in fact (and according to the much superior pocketgpsworld) there
are quite a few to note.

I know some smart alec will say there's no need for TT on the island, but i
do 2000 miles a week on the mainland and just happen to have the TT in the
van whenever i return home.

The outstanding question arising from this lack of road speed is:-
How does TT calculate arrival times, etc, when it does not know how fast you
are allowed to go?.

I await your replies.

Rick.

Andrew

2006-09-19, 10:33 pm

On Tue, 19 Sep 2006 20:30:01 GMT, "Rick"
<rick.lyon@virgin.net-NO-SPAM> wrote:

>The outstanding question arising from this lack of road speed is:-
>How does TT calculate arrival times, etc, when it does not know how fast you
>are allowed to go?.

Probably the same way TTN5 does, it knows roughly what speed you will
do on a A or B road or motorway, and guesstimates pretty reliably from
there.
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Jack Erbes

2006-09-19, 10:33 pm

Andrew wrote:

> On Tue, 19 Sep 2006 20:30:01 GMT, "Rick"
> <rick.lyon@virgin.net-NO-SPAM> wrote:
>
>
>
>
> Probably the same way TTN5 does, it knows roughly what speed you will
> do on a A or B road or motorway, and guesstimates pretty reliably from
> there.

Also TT5N will adjust your arrival time as your speed increases or
decreases. You can see that when you stop for fuel. The ETA will also
increase or decrease when you slow or speed up for a few minutes.

It is not explained anywhere but I'd guess that T5N has the roads
classed by type or knows the posted speed limits and uses that, in
conjunction with your speed over ground and and known length of the road
vectors, to estimate your arrival time.

Interestingly, if you start a navigation with TT5N, look at the ETA,
leave then and and can maintain the posted speeds, I've found that the
ETA will be within a few minutes of the estimate over a 100 mile or so
trip.

Jack

--
Jack Erbes in Ellsworth, Maine, USA (jackerbes at adelphia dot net)
(also receiving email at jacker at midmaine dot com)

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