WGS84 datum

[Ballochboy]

Hi new 2 Geocaching and this is my first post.

was reading through some info on gecaching on geocache.com and noticed that I should have set me GPS to WGS84 datum. I have an old Garmin etrex which I have had for 10 years, and I have just bought "Memory Maps" - Adventurer 2800 because it works off British Ordnance Survey maps. Anyway I adjusted the datum on the Etrex to WGS84, but on the Adv 2800 it had UTM WGS84 instead of just WGS84.

 

Are both UTM WGS84 and WGS84 both the same datum ???

 

I do gecaching with my 6 year old daughter so I don't want to be seen suspiciously loitering around a cache site with a kid, when i'm not even in the right area.

 

Also looking for geocachers around the globe who will add me as their friend on the geocache web site. People who I can ask for advise or intends to come to the Loch Lomond area of Scotland and need advise from me.

 

Cheers

Ballochboy...

[+GPSlug]

Same datum. It's just that it would be UTM coordinates instead of lat/long.

[+Cardinal Red]

Hi new 2 Geocaching and this is my first post.

was reading through some info on gecaching on geocache.com and noticed that I should have set me GPS to WGS84 datum. I have an old Garmin etrex which I have had for 10 years, and I have just bought "Memory Maps" - Adventurer 2800 because it works off British Ordnance Survey maps. Anyway I adjusted the datum on the Etrex to WGS84, but on the Adv 2800 it had UTM WGS84 instead of just WGS84.

 

Are both UTM WGS84 and WGS84 both the same datum ???

 

I do gecaching with my 6 year old daughter so I don't want to be seen suspiciously loitering around a cache site with a kid, when i'm not even in the right area.

 

Also looking for geocachers around the globe who will add me as their friend on the geocache web site. People who I can ask for advise or intends to come to the Loch Lomond area of Scotland and need advise from me.

 

Cheers

Ballochboy...

Does your GPS have the NAD83 Datum? There is only about a 1 Meter difference between WGS84 and NAD83.

Edited August 19, 2010 by Cardinal Red

[Ballochboy]

Same datum. It's just that it would be UTM coordinates instead of lat/long.

 

Does your GPS have the NAD83 Datum? There is only about a 1 Meter difference between WGS84 and NAD83.

 

So UTM WGS84 is different to WGS84, what is the difference can someone explain it to me?

 

Both WGS84 and NAD83 datum on my GPS are UTM.

Edited August 20, 2010 by Ballochboy

[+dakboy]

Same datum. It's just that it would be UTM coordinates instead of lat/long.

 

Does your GPS have the NAD83 Datum? There is only about a 1 Meter difference between WGS84 and NAD83.

 

So UTM WGS84 is different to WGS84, what is the difference can someone explain it to me?

 

Both WGS84 and NAD83 datum on my GPS are UTM.

UTM vs. degrees/minutes/seconds vs. degrees/minutes are just different representations of the same location assuming you use the same datum for each.

Edited August 20, 2010 by dakboy

[+dfx]

So UTM WGS84 is different to WGS84, what is the difference can someone explain it to me?

 

Both WGS84 and NAD83 datum on my GPS are UTM.

you're confusing datum with coordinate format. those are two unrelated things, independent of each other.

[+agentmancuso]

Think of it this way:

 

Datum = a system of measurement

Coordinates = a convention of expression

[Ballochboy]

This is getting confusing now as no one is giving me the answer i'm looking for. Which is, are(UTM-WGS84) + (WGS84) the same thing just worded different, and if they are different whats the difference?

 

My GPS under Units in its settings doesn't list WGS84 but UTM-WGS84 and as I read this on Geocaching.com

Datum

A datum is something used as a basis for calculating and measuring. In the case of GPS, datums are different calculations for determining longitude and latitude for a given location.

Currently, Geocaching uses the WGS84 datum for all caches. Many maps still use NAD27, which can cause confusion if your GPS unit is set to NAD27. Always check your GPS to ensure that WGS84 is the datum before entering a cache coordinate into your unit.

WGS84

The most current geodetic datum used for GPS is the World Geodetic System of 1984 (WGS84). The significance of WGS84 comes about because GPS receivers rely on WGS84.

Geocaching uses the WGS84 datum by default. We also use the format HDDD MM.MM, which is a standard for GPS receivers (like the eTrex).

HDD means Hemisphere and degrees. MM.MM are minutes in decimal format. If you have any questions, you can either visit the forums or contact us directly.

It is critical that the format be correct, otherwise geocachers will be unable to find your cache!

 

So this is why I posted on the forum, to make sure I've set my GPS correctly.

[Ballochboy]

This is getting confusing now as no one is giving me the answer i'm looking for. Which is, are(UTM-WGS84) + (WGS84) the same thing just worded different, and if they are different whats the difference?

 

My GPS under Units in its settings doesn't list WGS84 but UTM-WGS84 and as I read this on Geocaching.com

Datum

A datum is something used as a basis for calculating and measuring. In the case of GPS, datums are different calculations for determining longitude and latitude for a given location.

Currently, Geocaching uses the WGS84 datum for all caches. Many maps still use NAD27, which can cause confusion if your GPS unit is set to NAD27. Always check your GPS to ensure that WGS84 is the datum before entering a cache coordinate into your unit.

WGS84

The most current geodetic datum used for GPS is the World Geodetic System of 1984 (WGS84). The significance of WGS84 comes about because GPS receivers rely on WGS84.

Geocaching uses the WGS84 datum by default. We also use the format HDDD MM.MM, which is a standard for GPS receivers (like the eTrex).

HDD means Hemisphere and degrees. MM.MM are minutes in decimal format. If you have any questions, you can either visit the forums or contact us directly.

It is critical that the format be correct, otherwise geocachers will be unable to find your cache!

 

So this is why I posted on the forum, to make sure I've set my GPS correctly.

[+smithdk]

This is getting confusing now as no one is giving me the answer i'm looking for. Which is, are(UTM-WGS84) + (WGS84) the same thing just worded different, and if they are different whats the difference?

 

My GPS under Units in its settings doesn't list WGS84 but UTM-WGS84 and as I read this on Geocaching.com

Datum

A datum is something used as a basis for calculating and measuring. In the case of GPS, datums are different calculations for determining longitude and latitude for a given location.

Currently, Geocaching uses the WGS84 datum for all caches. Many maps still use NAD27, which can cause confusion if your GPS unit is set to NAD27. Always check your GPS to ensure that WGS84 is the datum before entering a cache coordinate into your unit.

WGS84

The most current geodetic datum used for GPS is the World Geodetic System of 1984 (WGS84). The significance of WGS84 comes about because GPS receivers rely on WGS84.

Geocaching uses the WGS84 datum by default. We also use the format HDDD MM.MM, which is a standard for GPS receivers (like the eTrex).

HDD means Hemisphere and degrees. MM.MM are minutes in decimal format. If you have any questions, you can either visit the forums or contact us directly.

It is critical that the format be correct, otherwise geocachers will be unable to find your cache!

 

So this is why I posted on the forum, to make sure I've set my GPS correctly.

 

Most GPS units have a separate setting for the datum and format. Is your only option UTM-WGS84 regarding WGS84? The cache pages do list the coordinates in UTM format also.

[+dfx]

UTM is a coordinate format.

longitude/latitide is a coordinate format (and has different flavours, depending on whether you use minutes/seconds or not).

the british grid is a (local) coordinate system.

etc.

 

wgs84 is a datum.

nad83 is a datum.

nad27 is a datum.

 

a datum is a reference model of the earth, and a coordinate format is used to express a location on that model. understand now?

[+Rotareneg]

This is getting confusing now as no one is giving me the answer i'm looking for. Which is, are(UTM-WGS84) + (WGS84) the same thing just worded different, and if they are different whats the difference?

 

My GPS under Units in its settings doesn't list WGS84 but UTM-WGS84...

 

So this is why I posted on the forum, to make sure I've set my GPS correctly.

 

The confusion is that most GPS units (like your older eTrex) have separate settings for the coordinates and datum, but your new one apparently doesn't. If the only available option that includes WGS84 is "UTM WGS84" just use that and use the UTM coordinates listed for the caches.

 

I tried looking for a manual for your GPS but the only one I could find didn't have any useful info at all.

[Ballochboy]

 

The confusion is that most GPS units (like your older eTrex) have separate settings for the coordinates and datum, but your new one apparently doesn't. If the only available option that includes WGS84 is "UTM WGS84" just use that and use the UTM coordinates listed for the caches.

 

I tried looking for a manual for your GPS but the only one I could find didn't have any useful info at all.

 

I did notice that the etrex had both "Position Format" & "Map Datum" And Memory Maps Adventurer 2800 GPS only has "Position"

 

So do you think it's best if I set my GPS to UTM WGS84 or Deg/Min

[+ecanderson]

So do you think it's best if I set my GPS to UTM WGS84 or Deg/Min

What you want for caching is WGS84 with Deg/Min, so I'm guessing you are supposed to select the latter. Strange user interface there..

[+dfx]

So do you think it's best if I set my GPS to UTM WGS84 or Deg/Min

deg/min. that's assuming it's using wgs84 underneath of that, which it probably does.

 

for traditional caches the coordinate format won't make much of a difference, but for multis and mysteries deg/min is going to be much more convenient, because that's what almost all coordinates will be in.

[Ballochboy]

So do you think it's best if I set my GPS to UTM WGS84 or Deg/Min

deg/min. that's assuming it's using wgs84 underneath of that, which it probably does.

 

for traditional caches the coordinate format won't make much of a difference, but for multis and mysteries deg/min is going to be much more convenient, because that's what almost all coordinates will be in.

 

Set both Memory Map on my PC and Memory Map Adv2800 GPS to Deg/Min.

 

The best answer I have had Cheers Mate!

[Guest]

Can anyone tell me if WGS84 is the most accurate datum to use in the UK? I heard something about OSGB could this be better?

[+Viajero Perdido]

In a nutshell: For geocaching, you need to set your unit to:

Map Datum: WGS84

Position Format: hddd° mm.mmm'

 

Your choice of datum affects what numbers your GPS will show at a given location. By convention, all geocaches worldwide are supposed to be recorded with WGS84 datum. Using the wrong datum will have you looking in the wrong place. All datums are equally "accurate", so using the wrong datum will "accurately" point you to the wrong place.

 

If you've manually entered some coords in your GPS while it was set to some other datum, you'll need to re-enter them again after switching to WGS84.

 

Hope that clarifies.

Edited January 28, 2011 by Viajero Perdido

[+dfx]

Can anyone tell me if WGS84 is the most accurate datum to use in the UK? I heard something about OSGB could this be better?

 

As far as pure positioning goes, no datum is better than another, they all just give you some numbers that correspond to some location on the planet. Some datum's model of the earth may reflect the real earth more accurately than another and thus the numbers you will get for a certain location will be different, but that's not really relevant to you if you just want to find a certain location. You just need to make sure you're using the same datum as the coordinates given.

 

However, OSGB most commonly doesn't refer to a datum, but rather to a grid reference system, like UTM. It's a different way of expressing locations on the earth, different from coordinates in longitude and latitude degrees. Instead, it's a rectangular grid, which needs an underlying datum to work on. For OSGB this is the OSGB36 datum, while for UTM it's usually WGS84. But it doesn't have to be, any grid can be applied on almost any datum, it's just going to change the numbers you get for the locations.

Edited January 28, 2011 by dfx

[Guest]

Can anyone tell me if WGS84 is the most accurate datum to use in the UK? I heard something about OSGB could this be better?

 

As far as pure positioning goes, no datum is better than another, they all just give you some numbers that correspond to some location on the planet. Some datum's model of the earth may reflect the real earth more accurately than another and thus the numbers you will get for a certain location will be different, but that's not really relevant to you if you just want to find a certain location. You just need to make sure you're using the same datum as the coordinates given.

 

However, OSGB most commonly doesn't refer to a datum, but rather to a grid reference system, like UTM. It's a different way of expressing locations on the earth, different from coordinates in longitude and latitude degrees. Instead, it's a rectangular grid, which needs an underlying datum to work on. For OSGB this is the OSGB36 datum, while for UTM it's usually WGS84. But it doesn't have to be, any grid can be applied on almost any datum, it's just going to change the numbers you get for the locations.

 

Excellent, thank you. i think i'll stick to WGS84 then, i tend to find British grid and utm a bit confusing!