What Do You Do When Mapping Data Disagrees

Well, I had a route bookmarked in Google Maps that I've never yet driven. I made Google Maps output a .kml file, converted it to a .gpx file, and loaded it into Mapsource (CNNANT2010 maps) only to find that the route I had in GM wouldn't work in MS because MS didn't admit the existence of a road that I'd routed over in GM. So, I fired up S&T2009 and SA2009 to see what they thought about the road. None of the digital mapping packages othe than the TeleAtlas GM is using admit there's a road there. Determined to get to the bottom of the issue, I went to the USGS and downloaded the 7.5 arcminute (1:24k) quads for that area. The road is present on the USGS quads as a "Unimproved Road". I hunted around a bit and there are several roads in that area maked as "Unimproved Road" on the USGS quads that are present in the Garmin, DeLorme, etc map sets. It's just this one road (that I've found so far) that's present in the USGS and TeleAtlas but not the others.

So, working my way around to the actual question, is there any way to figure out which map data to trust without actually going there to physically confirm the existance of the road?

Why don't you get Garmin Topo maps for the area that interests you. I don't think they are locked and (if they are like the Canadian ones) they are routable.

Terry

That's actually something I'm strongly considering doing. However, even then, the question remains of what to do when the multiple mapping sources disagree. I'd like to think that the USGS quads are the most accurate mapping data available, but it's entirely possible one of the commercial companies knows the road has been abandoned or gated off.

Google uses TeleAtlas while all the rest except Delorme use NavTeq. It is unlikely the sources will all agree particulaly on secondary/ tertiary roads and gates on those. I don't think you could depend on any source, even the quads for up-to-date information on that sort of change.

Even if they are using the same topo information, there is a considerable lag between when the information becomes available (if it does) and when it appears in a mapping program. Garmin and Delorme both do Topo but I have no experience with the Delorme Topo product.

Terry

In some cases you simply won't see really minor roads appear in the street maps. You will see more of them in digital topo maps but not necessarily all of them. It depends on the source of the map data that the map data aggregator (eg. Navteq, TeleAtlas, DeLorme) is using. And it depends on the accuracy of the data input by the mapping techs who actually input the data.

The road you see on the USGS map and Google Maps might still exist. But it might no longer be passable.

A possibility for getting the truth of the existance of a particular road is to provide some detail about its location and see if anyone on here is able to check it out for you. Pick a point on the road in question, or the start and end of the part that does not appear on some of the maps, and provide the coordinates. There's no guarantee that anyone here lives nearby but you never know unless you ask and provide sufficient data.

...ken...