I'm new here so a few questions:
1. Where does the location data (lat, lon) come from? I ask because I'm an RVer and have made files for Flying J, TA, Petro, and Pilot. It ain't easy, and I appreciate the effort.
The initial location for these POIs I made came from the company info. Very little of it was accurate about location. I spent a great many hours verifying the specific lat/lon using the earth shots from Google Earth. I was able to identify most locations by reading the sign at the facility. I was amazed at how far off the posted lat/lon was in many cases. Now, as of 2006, my locations for those truck stops are accurate.
2. Another important issue on interstate highways is just where is the location given -- at the exit or at the facility. Sometimes it makes a large difference and always makes a difference in the GPS instructions.
For interstate highway POIs I list where the included location is -- "Close to Flying J" or "Close to Exit."
3. When, and how, are the files updated?
4. By the way, I have checked some of the WalMart lat/lon from POI Factory with the same data from a paid source. There are some differences. Their statement is that their location info comes from the same source as Google and other web map search routines.
Most of the location data comes from Google with a fair amount from other sources such as Yahoo, personal observation and other sources.
Using Google Earth or MS's Bing 3D are options. If you are a programmer, you can use programmatic interfaces to some of these programs and submit a list of addresses and have the program return the approximate LAT/LON. If you use the API to submit a list, you need to check with what precision the program resolved the query. If it comes back anything other than address, you have to verify. GPSVisualizer will let you submit a list and get the precision returned as well as the coordinates as an option.
That's why you customize lists. Some like to have an alert sound when they approach a location. Unless you use TourGuide as part of the name you will only be alerted if the point is on your path. Most truck stops aren't next to the highway - or at least the exit you need. Same with stores and restaurants. it depends on who put the file together.
That's up to the maintainer on this site. Some are updated with any report of an error, some wait until there are enough to make it worth their time and some files are posted and never updated.
Wal-Mart happens to be one of the most popular files on this site. People are always submitting corrections as to coordinates and the maintainer does a great job of keeping up with them. I would trust the file from here for being correct than the location reported from something like Google.
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