Lat Long

I am not familiar with the format of the Good Sam lat/long values. Is it possible that they are in degree-minute-second (DMS) format and the GPS expects them to be entered in decimal degrees (DD)? Or it could be the other way around. The GPS also might want them entered in lat/long order but you entered long/lat.

That doesn't change accuracy, and it's pretty obvious what the format is just by looking at it. If the OP is building an app, I hope he is checking these locations against GE anyway.
The real question is what qualifies for a 25% error distance wise?

I had noticed an issue with GPS coordinates on rvparkreviews.com and submitted a support ticket. It sounds like they get the coordinates from wherever Google Maps thinks the address is. So it is likely the underlying map data that is incorrect. Good Sam probably does something similar - no one is actually looking at a map and capturing the coordinates. Instead their system probably calls a Google Maps function, gives it the address and it returns the coordinates of where the map data thinks that address is.

Or not. :h

For example, here is a web developer describing that very thing:

http://atomiku.com/2012/12/get-gps-coordinates-from-google-api-with-php/

I have always used http://itouchmap.com/latlong.html to get coordinates for any spot. Enter an address or town to get your map in the vicinity then blow it up until you can click on the entrance to the park (or whatever you need) and it gives you the lat, long to six decimal places, very accurate.

tkcas01 wrote:
I had noticed an issue with GPS coordinates on rvparkreviews.com and submitted a support ticket. It sounds like they get the coordinates from wherever Google Maps thinks the address is. So it is likely the underlying map data that is incorrect. Good Sam probably does something similar - no one is actually looking at a map and capturing the coordinates. Instead their system probably calls a Google Maps function, gives it the address and it returns the coordinates of where the map data thinks that address is.

I have also found many inaccuracies in park locations at RV Park Reviews. I usually send correcting info. It seems to me that they come from the first reviewer putting the location in and they just click on a point in the same town where the park is or don't drill down to click on an accurate position. I have found many erroneous locations several miles from where Google says the park is.

First I am fixing them.
Second I posted in beginning because I assumed this was a question that would be asked by someone not familiar with that book.
Third what I am calling a 25% error is the number of drop pins that do not fall any where in or at the park it's self. My question stems from the concern if the GPS locations are not verified what other information is also incorrect in the guide.

This thread won't last much longer. Mods must be napping.

From another post by the OP, he is creating an app from the Good Sam Directory. Legal?

Mr. Camper wrote:
This thread won't last much longer. Mods must be napping.

Why would the Mods shut down a reasonable discussion?

OP- Thats great you are fixing them.. Someone's gotta do it.. It's likely those numbers were taken years ago by someone not familiar with GPS or took it from some developing map site, some were really bad.

FYI- I use Goggle EARTH (not maps), and use those results to file microwave licenses with the FCC across the country, and it's HIGHLY accurate against any of the professionally surveyed sites I've used. In other words, whatever you come up with for the front gate on GE will likely be within a few feet.

When done, sell em' back to the publisher.. :)

This is a bit of a complex subject.

First: the earth is NOT round it is an ellipsoid.

Second: All Sat GPS coordinates are based on a "Datum" that can date back as far as the early 1920's or even the 1700's or as late as the 1980's There are many datums that can be used.

Also the earth is not "flat" ie. level all around it's surface. It's mountainous, has valleys etc. For GPS to work it must assume that the earth has an average elevation.

This means that for the purposes of "finding" your exact position and translating that to the ancient system of Latitudes and Longitudes means there will be differences from one gps system to the next depending on the "Datum" used.

If my memory serves, Nigel Calders book "How to Read a Nautical Chart" has a thorough explanation of how this all works and it's worth reading for anyone with a gps.

Therefore one GPS will give different sets of coordinates for a given place on the earth than another. Secondly the accuracy of the coordinate system is based upon which part of the earth you are on and how and when the land surveys were done.

My best advice: get and use a paper map. It dispenses with the coordinate system which is unnecessary on land. (for the most part)