Speed limit of the street.

[tukatz]

I got curious and did an experiment. I first found 4 decimal place factors for MPH to KPH and reverse. Then I setup a spreadsheet with 25, 30 and 35 MPH numbers. I converted them to KPH and then back to MPH using the Round function. They converted there and back and were still good numbers. Then I repeated the calculations using the Int function which, as I suspected, truncates rather than rounding. I got back 24, 29 and 34 MPH. Ahah! I changed the KPH to 1 more than the converted number and they converted back just fine with the Int function.

Then I fired up my 920 and changed the measurements to KPH and corrected the speed on a nearby street to 41 KPH. I planned a short run on that street and ran a demo and found that the speed had been stored as 40 KPH rather than the 41 I had entered. Needless to say, when I changed the measurements back to MPH and ran the demo again it was 24 MPH. It appears that KPH is rounded to 5 MPH increments and the conversion back to MPH truncates rather than rounding. So it is not the poor little pea brain of the 920, it is the poor little pea brain of the programmer.

 

[sageuvagony]

I got curious and did an experiment. I first found 4 decimal place factors for MPH to KPH and reverse. Then I setup a spreadsheet with 25, 30 and 35 MPH numbers. I converted them to KPH and then back to MPH using the Round function. They converted there and back and were still good numbers. Then I repeated the calculations using the Int function which, as I suspected, truncates rather than rounding. I got back 24, 29 and 34 MPH. Ahah! I changed the KPH to 1 more than the converted number and they converted back just fine with the Int function.

Then I fired up my 920 and changed the measurements to KPH and corrected the speed on a nearby street to 41 KPH. I planned a short run on that street and ran a demo and found that the speed had been stored as 40 KPH rather than the 41 I had entered. Needless to say, when I changed the measurements back to MPH and ran the demo again it was 24 MPH. It appears that KPH is rounded to 5 MPH increments and the conversion back to MPH truncates rather than rounding. So it is not the poor little pea brain of the 920, it is the poor little pea brain of the programmer.

Confirmed like dhn said, A BUG! Nice work tukatz

 

[tukatz]

Speed limit correction idea

It's too bad you can't enter speed limit corrections by marking beginning and ending points on a road. For example, Interstate 5 runs from Canada to Mexico. Its speed limit is not constant. In Washington it is either 60 or 70. In Oregon it is 65 except in certain areas. Much of California is 70, but parts are 60. If I select I5 as the road to change, I have to mark many short segments of a stretch that is 60MPH. If I could mark the part beginning just south of Tumwater, WA and ending somewhere north of Everett with just a few clicks and a little map scrolling, I could correct many miles of road with one correction. Anybody have any pull with TomTom re future changes?

 

[reddy]

Speed Limit use in Demo and Route estimations

I live on a gravel road just outside of town.
1. When my Go 720 calculates a route it estimates that it will take 14.5 minutes for the 1.2mile stretch that i live on ???
No speed limit on this road cause it is not a major road. But estimating a speed of 4.14mph ???
2. The next street is reported as unpaved which is wrong. I sent that in as a correction (under other, since the Go 720 cannot itself make that correction).
That street has the same issue, approx 29minutes for a 3mile stretch.
3. When replaying the route in Demo Mode it reports the car will be travelling at about 39mph???
Why is this different from the speed used for the time estimates.
4. On the Go 720 i was able to fix the speed limit to 55mph on both these stretches.
In the Demo mode the travelling speed is now updated to 55mph (except for slowdowns at the 1 turn).
However the time estimate used in the Route details has not changed one bit???
5. The impact of this is that when i plan routes from my home it goes through extra lengths to avoid the segments with the crazy estimates. And this results in routes that are super inefficient, about 8miles more than the direct route.

This seems like a software problem to me. Different speeds used for Demo mode and for Route estimation.

Should I be sending this in to TomTom.... Does TomTom respond pretty good, or do they pretty much ignore such stuff.
What do y'all think, any experiences?

The one customer service rep i talked to was pretty aggravating.

 

[dhn]

You could try to block the road on your unit using mapshare corrections and not offer to share with others. Presumably, TT won't select the blocked roads when tryong to plan a route.

 

[reddy]

I tried blocking the street and it does work.

But i reversed the change. I live about 1.2 miles into dirt road territory and it seems like, because of the extreme speed estimation on dirt roads the Go 720 does not find very efficient routes at all (despite the street blocking exercise).

Additionally a couple of the roads were paved a few years ago (around 8 years ago). This data is incorrect in the maps. And it seems that i cannot correct the road type in map-share, i can only report it. I reported the wrong road type using map-share.

The customer rep stated that road types are not alterable using map-share corrections that are downloaded, only via map updates that will need to be purchased at a later date.

Between not being able to fix road types and the routing section of the software not using speed limit alterations it seems like when routes involve unpaved streets i am stuck with very unreliable routes.

Any thoughts or ideas?

(( Also the speed it uses seems to be approx 5mph on dirt roads not 4.14 as i noted in my earlier post))

 

[MrChris]

Well I upped my TomTom to NavCore v8.3 for my 920 (Sine I have a good full backup I figure what could go wrong) . And I don't see much if anything visually different from the previous v8.010. The compass for my still is way off 90% of the time. I will be heading north but it says im going south/west.

And I can no longer play verbal instructions across my car stereo which isnt that big of a deal since it was kinda imbarsing when I would be sitting at a stop light with my radio blaring only to have everyone at the intersection know that I need to make a left at the next light. LOL.

MC