Accuracy of POI data
Mon, 01/12/2009 - 11:27pm
 15 years
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I just subscribed and downloaded a number of custom POI from the POI Factory. I wanted to see if the McDonalds inside the local Walmart was there. That POI did come-up and the address provided was correct, however the longitude and latitude were W A Y off and in simulation driving mode, the Garmin drove to a place four miles from the McDonalds in question and indicated that it was in the median strip of a local freeway.
What controls or checking is used to verify the accuracy of the information in the POI files? I cannot afford driving miles out of my way because of incorrect information.
Mark
You are the control
Members provide the original data, members provide quality control by reporting errors.
Tuckahoe Mike - Nuvi 3490LMT, Nuvi 260W, iPhone X, Mazda MX-5 Nav
Yep...
A good friend just downloaded the Starbucks POI and it did not contain either of the two Starbucks that are in our hometown. It was supposed to have been updated in December.
You can contact the author of the POI and suggest a correction.
Garmin GPS: The cat's meow!
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What controls or checking is used to verify the accuracy of the information in the POI files?
The redlight and speed camera files are verified by the site (Miss POI). The other files are as good as the contributor. With the big files, it is virtually impossible to verify every location -- most are batch geocoded from addresses provided by the company. Sometimes, I've seen bad coordinates provided by the company.
Nuvi 660 -- and not upgrading it or maps until Garmin fixes long-standing bugs/problems, and get maps to where they are much more current, AND corrected on a more timely basis when advised of mistakes.
garbage in garbage out
Not infrequently a list of "addresses" provided will be extremely vague. For example, the address might be given as just "Highway 12". Hopefully the POI contributor will notice this when geocoding and do at least two things if he or she can't find more accurate coordinates:
1) make sure that the coordinates at least point to the general Location. Looking up coordinates for something like "Highway 12" will sometimes return coordinates for a completely different state (even if you provided the original state and even zip code), so it's good to zoom out on the map and see if you are at least on in the right state or country.
And 2) Make a note in the POI that the address is suspect and the coordinates may be off, plus as much other information as you have (such as a shopping plaza or mall name). This may help warn users that the coordinates are not exact, and may get good coordinates reported much sooner.
And if
you find a POI that is inaccurate and make a correction, you can use google maps or any other satellite photo sites to see the spot if you remember the location. I verify mine using google earth.
Mike
User supported.....not just created!
A good friend just downloaded the Starbucks POI and it did not contain either of the two Starbucks that are in our hometown. It was supposed to have been updated in December.
You can contact the author of the POI and suggest a correction.
It also has to do with data availability. For example, when I go to the Starbucks website and look at the stores near me, only the free standing stores appear. The stores in Barnes and Noble, Target, etc don't appear. So the user obtains the info from the website and puts it out for the users to help maintain.
That explains...
the ones missing in our hometown. One location is actually within a hospital and the other is in a Barnes and Noble.
Garmin GPS: The cat's meow!
Address Problems
My Garmin has address problems in general. It thinks my mother-in-law's house is about a half mile up the road from where it actually is, based on entering the address.
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This is typically an issue with how the map data represents the data. The map doesn't really 'know' where every address is actually physically located. Instead, it knows that a certain street segment contains a certain range of addresses. Then it attempts to place the addresses along the segments. Sometimes it it less accurate than other times.
Address accuracy and safety
I have a similar problem, according to my machine I don't think our house exists! When it's turned on in the house it says the nearest address is about three houses away. Could be useful if it ever gets stolen, the thief won't be able to find our house
On that topic I got a tip from someone else that uses a GPS that I think makes sense. When you enter your home location, enter it as somewhere close to but not your actual address, mine is the intersection at the top of the road. That way if someone does steal your car or jacket with your GPS and keys in it you won't be giving him the directions to the door the keys open! If you use Garmin Lock then make the security location a block away, not your house, on the same reasoning - if he learns your address (e.g. from insurance docs in the glove compartment) then he can come there and unlock it, mine is the parking lot of the local coffee shop.
On the latter topic, does anyone know the radius of the security location effectiveness? 10 yards, 100 yards, half a mile? Would I have to park in the exact same spot to unlock it?
Wrong Town
I was working on some pois this morning and one was geo-coded 20 miles from the actual location in a completely different town. I looked up the name of the establishment in google, used the establishments map, and determined the correct location. Hopefully, the geo-coding will get you to within sight of where you are going but don't bet on it.