Team Kender Posted May 9, 2003 Share Posted May 9, 2003 I hope this question makes sense... Lets say I'm looking for a cache that is in WGS84 datum and on the same trip I'm looking for a benchmark which is in NAD83 datum. I make sure that when I input the cache coords my MeriGreen is set to WGS84 first. Then I set the datum to NAD83 and input coords for the benchmark. If I do this will each waypoint remember which datum it was set with? Or do I need to make sure and have the MeriGreen's datum set to NAD83 when benchmark hunting and set to WGS84 when caching? Team Kender - Willow and Dan exploring the Bay Area backroads! Quote Link to comment
+Poindexter Posted May 9, 2003 Share Posted May 9, 2003 It makes no difference unless your using a paper map to navigate with. In that case, you would need to change the receivers datum setting when plotting your position on the map. Also, there is no difference between WGS84 and NAD83 as far as your receiver is concerned. The actual difference is so small that your receiver makes no conversion. Quote Link to comment
+Renegade Knight Posted May 9, 2003 Share Posted May 9, 2003 Poindexter is right about the two datums you mentioed. But Topo's and some things use NAD27 which is about 300' give or take off of WGS84. So... what you need to do is when up upload a waypoint in NAD27 to your GPS have your GPS be in NAD27. Then when you upload WGS84 have your gps be in WGS84. When you switched the GPS from NAD27 to WGS84 the existing waypoints are automaticly converted to the new Datum. If you switch back all the waypoints (including the WGS84 one) are switched to NAD27. Convoluted but it works. At least so far as I've checked. ===================== Wherever you go there you are. Quote Link to comment
Team Kender Posted May 9, 2003 Author Share Posted May 9, 2003 Thanks for the answers, it's good to know that WGS84 and NAD83 are that similar. But it means I'm either doing something wrong or the Geodetic survey info is off for the benchmarks I've looked for so far. One was so far off that there was no hope of finding the benchmark based on the survey description. And then the one I found this morning was off by 25 feet or more. I know the GPSr is working correctly though as it has taken me to 0 feet of a cache and it was indeed right there under my feet. I'll keep plugging away on benchmarks to see if I'm consistantly off. Team Kender - Willow and Dan exploring the Bay Area backroads! Quote Link to comment
+user13371 Posted May 9, 2003 Share Posted May 9, 2003 quote:Originally posted by Team Kender:I'm either doing something wrong or the Geodetic survey info is off for the benchmarks I've looked for so far. On the benchmark datasheets, some have ADJUSTED coordinates, which should be pretty close. Others have SCALED coordinates, which can be off by quite a bit as you noted. The reason is explained here under the heading of Why do the coordinates of some benchmarks seem to be way off? about a third of the way don the page. For that and other reasons, I usually DON'T use the GPS to find the benchmarks. I use datasheet measurments from local landmarks to find the spot. When I find it, then I check the GPS to see how close it was. --- LDR. [This message was edited by Lee David Rimar on May 09, 2003 at 06:25 PM.] Quote Link to comment
Team Kender Posted May 9, 2003 Author Share Posted May 9, 2003 quote:Originally posted by Lee David Rimar: quote:Originally posted by Team Kender:I'm either doing something wrong or the Geodetic survey info is off for the benchmarks I've looked for so far. On the benchmark datasheets, some have ADJUSTED coordinates, which should be pretty close. Others have SCALED coordinates, which can be off by quite a bit as you noted. The reason is explained http://www.geocaching.com/mark/ under the heading of _Why do the coordinates of some benchmarks seem to be way off?_ about a third of the way don the page. For that and other reasons, I usually DON'T use the GPS to find the benchmarks. I use datasheet measurments from local landmarks to get find the spot. When I find it, _then_ I check the GPS to see how close it was. Wise words Lee, I think I'll try a benchmark I failed to find with GPS using just the description. And let ya'll know how it goes. That will be next week sometime when I'm back in that area. Thanks! Team Kender - Willow and Dan exploring the Bay Area backroads! Quote Link to comment
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