poi location

If the CSV file you downloaded was a home-made POI list, I'll bet the discrepancy is just caused by some inaccurate operation (i.e. clicking on the map) of the CSV file author.

That would really be hard to answer.Some users may have visited the location and reported the coordinates.Some could have use the street address to verify the coordinates.Possible using Google Earth they were able to zoom in real close to find the building.If you have found some problems the best thing to do is contact the author of the file or files.Use the contact tab on the file and email the author.

It depends on a number of things.

There are variety of ways to get the geo coding and they don't all allow a satellite view and/or the contributor di8d not switch to that mode to drag the POI to the proper location based on the satellite view. Programs such as Easy POI Editor and GEEPEXX allow this, but Streets and Trips does not.

Addressing can leave a lot to be desired. The geocoding uses an algorithm that determines the street number location, but it is a calculation and variations occur.

I did a file for KIA Canada and the addressing for some locations were often postal addresses or worse and I had to go to the KIA Dealer website to determine the location as best as I could. In some cases, I just gave up.

Last but not least, this is a volunteer site. People generally do the best they can, but some are in a bit too much of a hurry.

Were the POI locations accurate enough to get the job done? Did you also plot the coordinates of the POI files on Google Earth and see if they were far off? Many times coordinates are plotted at the driveway entrance to a POI. There are other reasons why a POI is not where you think it should be; for instance, the Rest Areas POIs are on the road just before the exit ramp to each rest area.

Google Earth makes you think it is very accurate, because seeing is believing, right? Well, the only real test is by marking a known position (such as your driveway entrance) with your GPS, getting the coordinates, and then viewing it in Google Earth. It is not going to be exactly right most of the time. I think Google Earth is good, but it is not 100% accurate for every POI all the time.

Most POI files available for download were obtained from an electronic map - the map in the GPS, or Google Maps, or MapQuest. These may not match Google Earth exactly. A POI that was obtained from Google Earth is always going to look exactly accurate in Google Earth. This does not mean it is accurate.

dobs108

I created a POI for one of my work locations in Google Earth and when I arrive there, the location is about 100 feet away. I didn't use an address but instead placed the POI exactly where I park., so there was no geocoding error. The error is in the image overlay.

On a couple of the POI files that I manage. The actual coordinates cannot be placed at the address location due to current security requirements.
For example;
1) The file named Billeting_Directory_VI places you at the closest entry point or gate to the Military Base.
2) The file for MD Ranges places you at the enterance to the facility OR at the point where you leave the hardball road. All of these locations tend to have good signage to direct you to the actual range.

I am still new to this GPS thing and the reason for my question was, when I corrected the poi locations for nearby CVS, walmart, Sams club in the respective csv files by pointing to approx entrance of the buiding on google earth my GPSer got more accurate for those locations. I recognize as everyone might agree it is a very difficult task to verify every poi location in the so many poi files and since I am still new using the GPSer I was just wondering for the reason of the discrepancy.
Thanks to all for their informative responses .

You raise a good point. And there are a lot of reasons why.

As mentioned in this thread (have a look) 'Nothing Is Perfect' http://www.poi-factory.com/node/30656

The other thread mentions map discrepancies but another map not mentioned is the one in your GPS'r just to complicate things! For any given point, they all can differ in exact (reported) position of features.. roads OR imagery.

And just to make it worse.. even eliminating atmospheric conditions, where EXACTLY your GPS'r says you are can differ.

As an example, to follow up my post in the other thread I went outside today with my nuvi 765T and 200W to see where they said my driveway apron was. Both turned on at the same time, reporting the same accuracy (17ft & 18ft), using more than 7 satellites, held next to each other in my hand. They differ from each other by 35ft Lon and 70ft Lat! It's enough to make a difference of which side of my street, and my driveway vs. my neighbors.

Now I'm just amazed that I find as much stuff as I do.

If the POI gets me close enough that I can see what I am looking for, I am a happy camper.... While it may be nice to get directed to the front door of the location, it is certainly not required.

That's true 99.9% of the time for me as well, but the Williamsburg walking tour file, and some of the City project files here come to my mind with all of the room for error 'baked-in'.

Although I DO need to walk more according to my Dr.