off by 100 metres or so for addresses

[21rouge]

I use my 730 alot.

This afternoon and tonight something was up in that the unit would "reach its destination" often 100 metres or more from the actual location. It was easy to see this as the destinations were basic home addresses.


As well I have had no HOME updates since sometime this morning.

Have others had updates in the last 12 hours?

 

[Gilbert]

Addresses are not individually stored in TT maps. It basically works like this: within a street block addresses start at xx and finish at yy. Say there is a possibility of 300 unique addresses, they would be put evenly within that block so the midrange address would fit right in the middle. In practice, it does not always work this way and addresses are often off by some meters.

This afternoon, I needed 3 attempts to get the MapShare update work with some lack of response on TT servers. At times, Home will tell you there is no MapShare updates but is more a problem with their servers than the reality. A few days later, it will give you a larger update. When I originally got my TT, I would update nearly every day and now do it every 5 days or so which seems to serve me right. I normally do it late at night so the servers are not too busy and quite responsive vs in the middle of the day.

 

[21rouge]

Addresses are not individually stored in TT maps. It basically works like this: within a street block addresses start at xx and finish at yy. Say there is a possibility of 300 unique addresses, they would be put evenly within that block so the midrange address would fit right in the middle. In practice, it does not always work this way and addresses are often off by some meters.

Thanks for the explanation. It is just that I never noticed such inaccuracies (off by 100 metres on a residential street) with a Magellan I was test driving a month back.

I guess it should be very accurate for the first and last address on a street?

 

[dhn]

My house is always shown 8 away from the real location.

 

[21rouge]

8 metres wouldnt lead to confusion but I was easily a hundred metres off on two different residential addresses yesterday. That seems alot even given the way Gilbert has described the determination of the location of an address on a street. The Magellan 4250 was so close to the actual location that I never noticed such a discrepancy.

 

[ChillyCat]

For the most part, my 720 is never more than a house or two away from most address's. [in U.S.]

100 metres = 109.36 yds. That's prolly 3-4-5 houses in most neighborhoods.

I don't do Canada much, but i've most defffinatly noticed the accuracy of TT
mapping ain't all that good up there. Years ago, while using my Axim PPC w/V 6-7 maps, I got into all kinds of problems. Way way off most address's.
Just recently, I did a delivery in Kitchener, ON. [V8 maps] Once again I realized the accuracy sux'd just as bad as years old maps. Carrier Atlas to the rescue -AKA- good ole paper.

IMO - Canada just ain't getting the luv from the mapping gods. You'll find many a post at GPS specific forums address'ing this very issue.

 

[21rouge]

For the most part, my 720 is never more than a house or two away from most address's. [in U.S.]

100 metres = 109.36 yds. That's prolly 3-4-5 houses in most neighborhoods.

IMO - Canada just ain't getting the luv from the mapping gods. You'll find many a post at GPS specific forums address'ing this very issue.

But the method that Gilbert described re the way TT determines an individual address wouldnt depend on a map's accuracy (assuming the address is shown in the unit).

 

[ChillyCat]

Not real familiar with HOW it gets me there.......

BUT, there's a general consensis that Canada's accurcy is off.

 

[21rouge]

Addresses are not individually stored in TT maps. It basically works like this: within a street block addresses start at xx and finish at yy. Say there is a possibility of 300 unique addresses, they would be put evenly within that block so the midrange address would fit right in the middle.

Gilbert are you sure it works like this?

The reason I ask is that for kicks I entered the two addresses in Google Earth (I see 2008 Tele Atlas on the screen) that were off by 100 metres easy from their physical location. Well lo and behold Google Earth and Google Maps (satellite view) show the position of those two homes *exactly* where my GO730 told me that I had reached my destination! One address was 13 homes off the other 11 homes off. So there is nothing wrong with my unit per se it but it was a coincidence that both the addresses I went to yesterday were off.

But I am sure the Magellan I tested took me 'exactly' to the correct physical address of the one location that I had routed to with both machines . Maybe Navteq determines the location of individual address differently (better) than Tele?

 

[Buddharay]

well, magellan and tomtom have different map providers (navteq and tele atlas), whose accuracy varies depending on the area. my advice is to use mapshare or tele atlas's map insight to remedy your problem and propose a fix. google uses maps from both navteq and tele atlas, so that's not really a good way to judge.

 

[21rouge]

my advice is to use mapshare or tele atlas's map insight to remedy your problem and propose a fix.

Is Map Share able to report the type of problem I am describing i.e. specific address corresponds to a physical location x # of houses away from the intended home"?

 

[cputrdoc]

Is Map Share able to report the type of problem I am describing i.e. specific address corresponds to a physical location x # of houses away from the intended home"?

Not that I've seen, but that might be an "Other" correction. Navteq (Magellan's map provider) does allow you to submit that kind of correction.

 

[storm180]

I have seen the same thing with my 730 when I first got it. Everything was fine for a few days then I did an update and took it out and it showed me driving down a road I wasn't on , full signal and eveything, this continued for 17 miles then it corrected itself on the way home and when I got to my house it showed it 5 houses off. Now the day before I did the same route and every thing was fine. The only updates I did were a gpsfix and mapshare update.

I called tomtom the next day and they had me replace my application file. Took it out and it seemed to work and I have not had another problem with it since then. I do not download the gpsfix file evey time it is available, which takes me few more minutes to get a good fix but I have not been driving on roads that I am not on and once again my house is right on the money.

Obviously something happened and corrupted my application file, the only thing it could have been was the gpsfix file. Tomtom still could not explain what happened.

 

[Gilbert]

Gilbert are you sure it works like this?

The reason I ask is that for kicks I entered the two addresses in Google Earth (I see 2008 Tele Atlas on the screen) that were off by 100 metres easy from their physical location. Well lo and behold Google Earth and Google Maps (satellite view) show the position of those two homes *exactly* where my GO730 told me that I had reached my destination! One address was 13 homes off the other 11 homes off. So there is nothing wrong with my unit per se it but it was a coincidence that both the addresses I went to yesterday were off. But I am sure the Magellan I tested took me 'exactly' to the correct physical address of the one location that I had routed to with both machines . Maybe Navteq determines the location of individual address differently (better) than Tele?

Quite sure. It is a well known fact addresses are often off. The longer the road without intersection, the more likely it can be off. Besides, having each individual addresses' coordinates would take way too much storage on the maps when you consider the number of unique addresses for the USA & Canada. While 1 or 2 GB may seem huge it also is rather small when you consider all the data that needs to be stored. TT is having a headache with the new 930 models that are supposed to handle both NA and WCE maps on 4GB of internal storage. Remember that the digital maps we use are much more than paper maps with phonetic fields to handle voice recognition and tts, postal codes, one way streets, street and road names, road speeds, routing data, no left turn data, POI and much more. To my knowledge, there are no general maps that have individual addresses' coordinates publicly available. I know some municipalities' fire departments have coordinates of many manufacturing plants that handle hazardous materials and put such data on their gps but this is a different case.

 

[21rouge]

Quite sure. It is a well known fact addresses are often off. The longer the road without intersection, the more likely it can be off. Besides, having each individual addresses' coordinates would take way too much storage on the maps when you consider the number of unique addresses for the USA & Canada.

Hi Gilbert, I find this an interesting discussion .

But the way you describe the locating of specific addresses by a GPS is probably used by both Tele Atlas and Navteq?

But I can confirm that when I used the Magellan 4250 it got the one address (the only one that I routed with both machines) perfect .


And it just surprised me that the 'error' was perfectly reproduced when I located the addresss on GOOGLE Earth and Maps.

Does it make sense to report the inaccuracies?

 

[Gilbert]

Hi Gilbert, I find this an interesting discussion .

But the way you describe the locating of specific addresses by a GPS is probably used by both Tele Atlas and Navteq?

But I can confirm that when I used the Magellan 4250 it got the one address (the only one that I routed with both machines) perfect .


And it just surprised me that the 'error' was perfectly reproduced when I located the addresss on GOOGLE Earth and Maps.

Does it make sense to report the inaccuracies?

As I mentioned, the maps we have, have had some details removed in order to make them fit internal memory. After some scrutiny, some may determine that, because of the topology, they can skip each intersection and make the addresses fit to 4 intersections without losing too much accuracy and save x KB in the process for a region. I'm not saying this is what they did in your particular case as there may have been some errors in the original data. What you need to remember is they need to remove data to make the maps fit internal memory while remaining reasonably accurate. They won't reveal what they have taken out as it is considered some company secrets and prefer to boast about all they provide as it is more profitable for marketing.

As to reporting inaccuracies and them making it to released maps, it can be anybody's guess. On one hand, reports have it they are way behind in the workload and priority of it. MapShare updates are done without reports as to what they affect. You need to go into some hard to find file and you need to scrutinize the data to only know such and such state had updating data whose nature is unknown. I've given up looking at those files as they don't tell me much.

 

[21rouge]

within a street block addresses start at xx and finish at yy. Say there is a possibility of 300 unique addresses, they would be put evenly within that block so the midrange address would fit right in the middle. In practice, it does not always work this way and addresses are often off by some meters.

A business just opened on a street which is located in my neighbourhood. Although this street appears on my my 810maps it doesnt recognize any street #s (ie "House numbers not available for this street"). If addresses arent individually stored on the unit than shouldnt the unit 'estimate' where #98 is located? Or maybe it takes some sort of map update to enable street #s on a given street?

 

[Gilbert]

A business just opened on a street which is located in my neighbourhood. Although this street appears on my my 810maps it doesnt recognize any street #s (ie "House numbers not available for this street"). If addresses arent individually stored on the unit than shouldnt the unit 'estimate' where #98 is located? Or maybe it takes some sort of map update to enable street #s on a given street?

I don't know. If I was asked to guess the number, I'd ask if the street was in the same city? How does the TT know which city a street is in? It could come from two sources: 1- an index. 2- postal code information. I really don't know how it does it. Since TT employees are not allowed to help us here, I guess we'll never know...

OTOH, I know my first outing to Montreal's South shore with my TT was to an old vietnamese restaurant (Chez Lien on Victoria & Burton) in Greenfield Park that has been there for 20 years and the address was absent. Civic numbers on Victoria on that block were wrong. While TT's database may be useful, don't rely on it too much.

 

[Arno]

A business just opened on a street which is located in my neighbourhood. Although this street appears on my my 810maps it doesnt recognize any street #s (ie "House numbers not available for this street"). If addresses arent individually stored on the unit than shouldnt the unit 'estimate' where #98 is located? Or maybe it takes some sort of map update to enable street #s on a given street?

Remember this?
It seems that they pick the middle of the street in newly built areas.

 

[KIP536]

my 130s is always 1/3 mile off

i'm a first responder in a rural area. you can imagine the problem when tt tells me i have arrived at my destination and the residents are greeted with red lights and sirens only to discover the actual house is at least 1/3 mile up the road. tt used to tell me i could correct the situation with a new map, but that never worked.