Why Nad 83 For Utm Cordinates???

[AA1PR]

if all the usgs maps use NAD27 why does geocaching.com use NAD83 for UTM cordinates?? I know my magellan GPS310 is a few years old but never have had the need for nad 83 as all of the USGS maps i use for reference use NAD27. Also my gps doesnt have this nad83.Who or what maps have the nad83 printed on them for the cordinates?? Is this a newer system if so please explain as i'm not old but must be out of touch or something in the last few years??

Any help will be of important value to me and I thank you in advance.

[+tozainamboku]

It is not true that all USGS maps are NAD27. The USGS is converting over to NAD83 and newer maps use this datum. For GPS navigation purposes, NAD83 is virtually the same as WGS84.

[dsandbro]

On newer maps, whether NAD27 or NAD83, look near the SW corner for a small faint cross ( + ). This marks the quad corner in the other datum. If found, you can 'shift' the grid ticks to align with the the cross.

[+Greymane]

WGS84 and NAD83 are, in fact, independent datum, but the difference is negligible. It shouldn't be more than about a meter in most cases. The latest USGS maps are indeed in NAD83, but you have to remember that the USGS is only a portion of the available maps in circulation. We tend to think of things in terms of what we do here in the US, but there are dozens of map formats, datum and projections in use around the world.

[Tahosa and Sons]

If you use Nat Geo TOPO you can put UTM grids on the map using 27 or 84. So much more simple and functional than buying a map off the shelf.

[+Renegade Knight]

The reason is that WGS84 (NAD83) is the Datum used by Geocaching in general. When you convirt to UTM the Datum is kept the same. It's one less point of confusion than if you did a double conversation to NAD27 and UTM at the same time. Then someone else would ask why the points are not the same (they are but different datum) when they are using the WGS84 Datum to look at them both.

[AA1PR]

so if I use wsg84 this will be close by a meter or to. I know i'm new to this but have been using my gps since i got it for hiking purposes and hunting. I know of the tick marks on the maps and that is how i have lightly drawn the grids on my usgs maps. I just dont want to be off by say a half mile or so. Maybe this is the perfect excuse for the wife to buy me a new gps for my birthday. I orginally started off with the gps 315 but found i didnt like the built in map for accuracy and since i carry a map it was easier to look at the gps and take the reading and look at the map and go from there.

I thank all of you for the help.

73(best regards) AA1PR,Mike