Datum question

[tduncan53]

 I'm using the Calif Topo 2011 from this site on BaseCamp with and Oregon 450

What do I set as a datum on the SW and on the receiver?

Thanks Tim

[Seldom]

WGS84.  That should be the default for both.

[tduncan53]

Thanks for the reply!

I'm trying to learn more about the maps.  Was the datum listed somewhere in the description of the download page and I missed it?

Are most of the maps still based on the older datums?

I spend time in some areas where BLM, Indian reservations, and private land all intersect at some interesting angles and I'd like to as accurate as possible.

[Seldom]

I'm trying to learn more about the maps.  Was the datum listed somewhere in the description of the download page and I missed it?

Not likely.  WGS84 is the standard datum used for GPS maps.  Most GPSrs support other datums, and maps can be compiled using other datums but WGS84 is the default for the GPSrs and the compilers.

Are most of the maps still based on the older datums?

I'm not aware of any, but my experience is limited.  -Oz-, Indrid Cold, maps4gps, feel free to enlighten me, but I was under the impression that older datums were developed for older geodetic technologies, most of them paper.  Do you think you have a GPS map based on a datum other than WGS84?

I spend time in some areas where BLM, Indian reservations, and private land all intersect at some interesting angles and I'd like to as accurate as possible.

Sounds like you have good reason to avoid tresspassing.  What state are you in?  No big reservations around me, but lots of BLM.  60% of the state (UT), and the governor's suing the Feds to get it back.

[leszekp]

The native datum for the maps is WGS84, but you can choose any datum you need to use for either BaseCamp or your GPSr; both the software and the GPSr will automatically convert from WGS84 to whichever datum you select. Most modern datums are pretty close to WGS84 just about everywhere, so that's the best default choice; e.g. NAD83 doesn't differ from WGS84 more than meter anywhere in the continental US, less than the best stated Garmin GPS accuracy. But if you're using an older USGS topographic map and want to match coordinates on the map to the GPS, you should set it to NAD27 datum, as the difference in position between WGS84 and NAD27 can be hundreds of meters.

Just remember that the native coordinate system for GPS is geographic coordinates (lat/long), WGS84 datum; all waypoints and track points are recorded/saved in that format. If you choose a different coordinate system or datum, it is converted from geographic/WGS84 to be displayed, but internally it's kept in geographic/WGS84 coordinates.

[tduncan53]

Thanks leszekp and Seldom

I'm in SoCal and I also forgot the Camp Pendleton base maps are in MGRS.

I have a fixed GPS unit in my Jeep which only has lat/long read out so I'm excited to try out the Oregon in the field.

Thanks again to the forum for all the help and info.

Tim

[Boyd]

You might might find this interesting.... Using a Garmin GPS with paper maps.

[tduncan53]

Great link thanks!