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UTM


davejey

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When standing at a cache I take a reading on my basic etrex and it gives me a different UTM than is published on Geocaching.com. Therefore I can't use my etrex gps to go after caches published. Is there a setting I have to make on my gps?

I can go to a place and switch on my etrex , wait until it gets the satellites and then Mark and make a note of the number it is on (001- 009 etc numbers)

Cheers davejey

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In the op he states his utm is different than the website. While all the advice to change formats is good they don't address his original post. The website has utm listed below the WGS84 and he is comparing the two.

 

My question to the OP is how far off are the numbers? They will always be slightly different. If it is only the last one or two,digits that is not significant enough to affect hunting a cache.

 

Even if you change over to WGS84 the last digit or two will still be different from the website if you stand over the cache and take a reading.

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In the op he states his utm is different than the website. While all the advice to change formats is good they don't address his original post. The website has utm listed below the WGS84 and he is comparing the two.

 

My question to the OP is how far off are the numbers? They will always be slightly different. If it is only the last one or two,digits that is not significant enough to affect hunting a cache.

 

Even if you change over to WGS84 the last digit or two will still be different from the website if you stand over the cache and take a reading.

Thanks Walts and everyone. As an example -- the UTM given by geocach E329632 N5467251 which is refused entry into the etrex but which works for my Tomtom) The UTM given to my etrex standing at the actual cache is E2676431 N6029062

(which works for me to return to the cache position.) I will download the manual and work on it.

Cheers davejey

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I'd supply you with a link to download the manual, but of all the eTrex models, I don't have a clue which one you have.

 

You need to set the Datum and Format to: WGS-84 and HDD(D)° MM.MMM Datum and Format

Thanks Gitchee, I did this and it works,problem solved I can now use Lat & long instead of UTM

Cheers davejey :rolleyes:

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I'd supply you with a link to download the manual, but of all the eTrex models, I don't have a clue which one you have.

 

You need to set the Datum and Format to: WGS-84 and HDD(D)° MM.MMM Datum and Format

Thanks Gitchee, I did this and it works,problem solved I can now use Lat & long instead of UTM

Cheers davejey :rolleyes:

Just to help you get everything correct. UTM is lat long as is WGS. Both are different ways to say the same thing. Picture them as different languages.

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Just to help you get everything correct. UTM is lat long as is WGS. Both are different ways to say the same thing. Picture them as different languages.

This isn't correct. UTM and Latitude/Longitude are two ways to provide coordinates for a location on the Earth. Latitude and Longitude use an angle to measure an arc on the surface of the Earth, with latitude being the angle north or south of the equator and longitude being the angle east or west of the prime meridian (through Greenwich, England). UTM is a grid of 1 meter squares. There 60 zones around the world covering each 6 degrees longitude (with some exceptions here and there). The UTM Northing number is the number of meters (or grid squared north or the equator or 10,000,000 minus the number of meters south of the equator. The UTM Easting number is 500,000 plus the number of meters east of the central meridian of the zone or 500,000 minus the number of meters west from the central meridian of the zone.

 

The Earth is not perfectly a sphere and both UTM and Latitude/Longitude need to a have a reference (call a datum) that takes into account the shape (sometimes called the flattening) and the size (radius) of the Earth. WGS-84 is a datum. It is the one we use in geocaching because the GPS system uses this datum. However there are formulas that allow coordinates to be changed from one datum to another.

 

People who use a GPS unit along with a paper map will often set their units to display UTM using the datum that the paper map uses. This is not always WGS-84.

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