GPS lingo

[kano]

I am toying with the idea of buying a GPS. The one I am looking at is the Garmin etrex10(KISS)When the blurb tells me it will provide map coordinates does that mean it will give me a 6 figure grid reference for our topo maps and if that is the case does it also display the map series it is referencing. Can someone please explain?

[tastrax]

No it wont give a six figure grid reference but it is capable of giving you a full grid reference such as

56J 0526900(Easting) 7268344(Northing) - this could be shortened to something like 269683 to create a six figure reference

That should match your map so long as it has Universal Trans Mercator grids (versus something like Lat/Longs)

The GPS has no idea which maps you are using

[tastrax]

That should put you at about the NE tip of Fraser Island

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[Deltadog]

Google tells me the etrex 10 will give you a grid reference in MGRS (Military grid reference system).

My Garmin Dakota 20 gives me a 10 figure MGRS grid reference. (You can't change this to display 6 figure)

So, the Fraser Island example GR would be displayed like this: 56J NT 26900 68344

For a 6 figure GR, Ignore the last 2 numbers from each group: 56J NT 269 683

Check out this link for more info on MGRS. http://en.wikipedia.org/wiki/Military_grid_reference_system

[madmacca]

I can't speak for the etrex 10 specifically, but many GPS's allow you to specific the grid system in the settings.

GDA94 is the most common one in Australia, but there are others. Your topo map should say what system it is using.

[bernieq]

As you say, Kano, KISS - so I hope the following clarifies it for you.

The short answer to your question is :
grid reference :YES, it can
map sheet : NO, it can’t (but you don’t need it to)

and the longer answer is :
The Etrex 10 can give you a position reference that you can use to locate yourself on a map (for just about any map you are likely to have). You simply need to set the grid and map datum in the GPS to be the same as the map you have in your hand (and that’s why you don’t need the GPS to tell you what map you are using :).

As madmaca says, newer maps in Australia use a map datum of GDA94 (which is identical to the more universal WGS84 - your map will state what it uses) – older Australian maps mostly use AGD66.

The grid (or position format) also needs to be set in the GPS to match the map you are using. The 6-figure reference comes from the UTM grid but you can also use other formats (eg degrees/minutes/seconds).


So, have a close look at tastrax’s post – it explains where the 6-figure reference comes from. It’s a simplification of the full UTM reference. In the old days, the best you could read off a map was to the nearest 100m (so the last two digits were dropped off the Easting and the Northing numbers - leaving 6 digits).

[Rob A]

I have the older EtrexH. I doubt they have gone backwards.
Other than whats been said;
You need ot go Page/Setup/Units
Position Frmt "MGRS"
Map Datum "WGS84" (for the absent GDA94) providing your topo has a photo. If you have the older top, retire it. (The GDA94-AGD66 conversion is very easy, and its very easy to setup Etrex for AGD66, but you dont need to be caught out if ever you are under pressure.)
This will give you the simplest display with Grid Zone Designation, 100000 Meter Square Identifier, then the two five figure easting and nothing on separate lines.
Ignoring the last two numerals is easier than picking out the significant numerals from a line of seven.
I think its worth buying the topo of your own backyard for practice.

I still dont understand why few (edited from none) of the GPS units dont default screen to your position, in numerals even a blind man could read in the dark.
And I could care less what time the salmon are spawing in Djibouti and 99% of the dross served up as features.

[Ent]

I still dont understand why few (edited from none) of the GPS units dont default screen to your position, in numerals even a blind man could read in the dark.
And I could care less what time the salmon are spawing in Djibouti and 99% of the dross served up as features.

Fully agree. Sometimes you just want to read the co-ordinates and not have to hunt around for glasses. Big numbers and the datum would be very handy as a default screen easily accessed.

[bernieq]

Big numbers and the datum would be very handy as a default screen easily accessed.

Ummm, most (Garmin) GPSs can provide big numbers and the datum on an easily accessed default screen !

Gamin Colorado - UTM grid ref in large numbers

co-ords.JPG (70.77 KiB) Viewed 20973 times

Position Frmt "MGRS"

BTW, what’s with MGRS grid – assuming you're not in the Army, what (physical) maps use it? All my topographic maps sheets (Australia, at least) use UTM and DegMinSec. I’m yet to encounter an MGRS datum on a map. Please, enlighten me :)
.

[Rob A]

Well the smallest numbers on that screen are the eastings and northings.
Dont worry, on mine its worse. I had a colorado and oregon to trial but there were a few things I didnt like about em.
The idea of having MGRS is that five numbers are displayed, you discount the last two.
It lessens the chance of glance misreading, or picking out the middle of the numberset in the rain.

All my topos "effectively" have mgrs. Its a position format. Datum is still datum, WGS84, GDA94, whatever.
Ive yet to meet anyone without a ruler, calculator and pencil who can work things out in the bush using degrees minutes and seconds.
Ive seen people try to split degrees on a terrestrial map. Not a pretty sight.
Ill use decimal degrees outside in the ocean. No problems. Charts dont display grids.

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[Ent]

Hi

To avoid an argument the word default is key rather than if you can enlarge the display of the UTM location through exploring the menus. Below are three photographs from my much, err I will let each use their own word there, Garmin 62s. Now in a real world emergency the UTM co-ordinates where given to Search and Rescue which resulted in the pleasing sight of the helicopter bee-lining to the extraction point. Believe me in such a situation stuffing around finding and reading them is not as easy as sitting in a nice warm room but thanks to excellent team work I had a bit of time to find them while the first aid was being done by another group member. I think the default setting on the 62s was the last one.

Also Tasmap would sell one series of maps with one datum and another with another so you needed to swap between the two. None of the display options gives the datum that they are using. Err? and just in case some claim it is just me I was given a Garmin GPS to "recalibrate" as it was giving different co-ordinates to the others. I dropped to the fact that it was set on a different datum, but burrowing through a menu structure and trying to remember what datum is what given that the headline one on Tasmaps is often not the one on the unit so you need to find the phrase "similar to" on the map. Actually, a few GPSs find their way to me as I am suppose to be an "expert", a word I hate almost as much as "experienced", in GPSs. I wish I were but in the end I manage to figure them out despite stupidity of design in some.

The issue should not be one of geek superiority but one of sensible design and default settings. I am sure many people would appreciate a simple button push that gave in the largest font possible the UTM and the datum. It is amazing that the geeks fail to understand the mass confusion that exists out in the real world with all the different ways to give a position. For me it is an annoyance but I would be interested to know the percentage of people that buy a GPS and then it sits unused in the top of their pack until it even does not make it that far. A person familiar with map reading with a GPS that displays just UTM and the datum would have no hassles. It is the incessant marketing driven "necessity" to burden designs and menus down with "fish finding", etc that results in many people just giving up on what can be a very useful tool.

Regards

[tastrax]

I thought you would have done screen captures from the 62... now let me think, Menu, Menu, Setup, Enter, Display, Enter, Screen Capture, Enter, ON, Enter, OK, Page, (back to map screens), Power Button, connect USB, find folder Garmin\scrn .......

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[Ent]

And still no datum used display!

Now Tastax you are a very evil man with a remarkable memory for Garmin's multi layered menus. An impressive feat of studying manuals. For me a camera is easier.

Just goes to prove that the Garmin 62s can do it all if you live long enough to figure it out!!!!

Cheers

[Rob A]

Ent,
This is why it you set Datum to WGS84 and be done with it.
The MGR Position Format coordinate display simplifies the readout over the UTM.
You just start reading from the left and stop when you have read three numerals.
UTM readout is a bit chilly in inclement situations.

Screen shot 2013-07-02 at 11.14.19 PM.jpg (78 KiB) Viewed 20872 times

Obviously if you are in the far eastern state you flip over (position format) to NewzealandT or you will wind up in the wrong pass.

[Sparky]

Rob, only problem with setting the datum to wgs84 is that a large percentage of the current release Tasmaps are printed printed prior to 2003 so still based on AGD66 hence the need for us Taswegians to be competent at swapping between the two on our GPS's or risk being a couple of hundred metres from where we thing we are. Cheers Brett

[Ent]

Rob, only problem with setting the datum to wgs84 is that a large percentage of the current release Tasmaps are printed printed prior to 2003 so still based on AGD66 hence the need for us Taswegians to be competent at swapping between the two on our GPS's or risk being a couple of hundred metres from where we thing we are. Cheers Ent

Could not have said it better myself.

[sthughes]

I could. They are STILL printing them in ADG66!!! And only about 25% of the 1:25,000 series are done in GDA94! GRRR.

[Ent]

I could. They are STILL printing them in ADG66!!! And only about 25% of the 1:25,000 series are done in GDA94! GRRR.

After all it is Tasmap and they are "special" in that "special" sort of a way!!!

Cheers

PS it was so nice that the brushfire gave them six months over missing the last promised new map deadline an excuse to produce electronic versions. O'well at least they are consistent.

[tastrax]

The other thing to remember is that very few people actually communicate grid references correctly

Each of the six locations in the image below have the six figure "grid reference" of 400300 but they are in very different locations so the key part (in an emergency) is actually spelling out the full map reference (including the datum/projection and or map name/number) as listed on the bottom of most maps (as in previous images by Rob A - 1.jpg)

400300GridReference.JPG (136.49 KiB) Viewed 20772 times

[neilmny]

Great point Phil.
Personally I prefer UTM but that is because I started using it with my GPS and having read Rob''s post I've found that my GPS only has UTM (of the 2 choices discussed). Degrees blah blah of any kind is fairly useless in the bush.
The main thing is to use one system only, your GPS will detrmine your choice(s) then stick to it. In an emergency you've got to be able to get it right whether reading off a map or your GPS.

[Ent]

Hi Tastrax

Fully agree. We quoted the full UTM reference and the general area plus the datum. It must of worked. But it would be nice if it is possible to display the datum and the UMT in the biggest text size possible on the same screen.

Also we found the emergency response operators near hopeless until a Tasmanian overseer came on the line. Then it was easy. For example it took repeated attempts to convince the other operators that street addresses did not exist in the Western Arthurs. I kid you not they could not grasp this despite words like bushwalking, trekking, remote area and finally no $@"&@ roads for miles. It was great to hear "confirming that you are bushwalking in the Western Arthurs in Tasmania".

We on the same trip were given co-ordinate a for a short cut but goodness knows what was the reference as it miles wrong. So have experienced the vagueness of shortening co-ordinaries.

That is why I like a mapping GPS as you can get a good feel for the area to double check that you are not misreading position. On OSM I put mountain offshore of Japan by missing the minus sign.

However, nothing can beat a full size map though an iPad goes close. Maps are still good things to have.

Cheers.

[bernieq]

I prefer to explain rather than dumb things down, so if you are struggling with datums, grids, co-ordinates and how it all works with GPSs and maps, hopefully the following will help a little.…. (and apologies for the long post).

from an AGD66 map

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On a map, the :
DATUM : defines how the map is drawn (ie the mathematical model used to ‘flatten’ the real spherical Earth onto a flat map). For Australia, most likely your paper map will be GDA94 (= WGS84) or AGD66. For NZ, new maps will be NZGD2000.

GRID : is the horizontal and vertical positional lines drawn on the map – most commonly in Australia is UTM (universal transverse mercator), in NZ – NZTM2000 but can be anything – you could even draw your own lines on the map and use those (although not much good if you want to explain where you are to someone else). Other examples of grids are MGRS (military) and BNG (British), DegMinSec (almost all maps have this last grid but accuracy is an issue).

Co-ordinates : are the grid numbers and/or letters that define your position on the map – the actual numbers/letters depend entirely on the datum and grid being used.


One of the primary uses of a GPS is to give you a position – you then use that to find where you are on the map you are carrying. In this situation, the GPS settings must match the map (or you’ll not be able to place the GPS position correctly).

Further, if you had to give a position to someone else (eg Search and Rescue, 000, Parks etc) then you would need to tell them enough positional information to locate you uniquely – which usually means the map datum, grid and co-ordinates.

The MGR Position Format coordinate display simplifies the readout over the UTM.

The problem, IMO, in using the MGRS grid is the potential for confusion when relaying co-ordinates to someone else.. Yes, MGRS is effectively the same as UTM but a full grid reference is expressed differently : 54HXD 71880 71675 (MGRS) is the same position as 54H 671880 5871675 (UTM).

So, where does the 6 digit reference come from? 54H 671880 5871675 = 718 716. BTW, the UTM grid is measured in metres so 671675 is 5 metres from 671670.

Now, when reading a paper map, you don’t have pinpoint accuracy – to the nearest 100m is as good as can be expected – so it is customary to drop off the last two digits. Also, if you name the mapsheet you are using (in this case, Ararat) then you don’t need the square (54H) or the first couple of digits so it is sufficient to say “Ararat 718 716”. BUT, it is not wrong to give the whole reference – in fact, in these days of digital data, I agree with Taztrax and Ent that it’s better to give the full position reference (including the datum and grid).

Dumbing it down so the GPS just gives a 6 digit reference means communication with the rest of the world is compromised (not a good thing if you need rescue or are trying to find a hut in a white-out etc etc).

Ent, many (all?) Garmin GPSs provide for profiles. I have 3 set for bushwalking : each with a different datum/grid and background colour : AGD66/UTM, GDA96/UTM and NZGD2000/NZTM2000 – all I need to do is change the profile to suit the map I’m using.

[Ent]

Thank bernieq for explaining the mystery of the six digit number sequence and giving an excellent suggestion to use the profile to optimize the Garmin GPS for the maps rather than digging down into the sub menus for swapping between datum. Different coloured backgrounds make excellent sense. Thanks for proving yet again that this forum can add real value to bushwalking knowledge. Much appreciated.

Cheers

[Rob A]

Each of the six locations in the image below have the six figure "grid reference" of 400300 but they are in very different locations so the key part (in an emergency) is actually spelling out the full map reference (including the datum/projection and or map name/number) as listed on the bottom of most maps (as in previous images by Rob A - 1.jpg)

400300GridReference.JPG

Tas,

With respect to MGRS position format You are completly wrong.
If you call a reference, it will have the 100,000 square meter reference letter.
56H, ok bang tp rights youve busted me in Aus over the rhs and half way up. (Or actually the prime meridian of the universe )
LJ, Lima Juliet, youve a damn good idea Im in Lake Mac, Nothumberland. Everyone is now in hte same page, Swansea 9231-4N. Good start huh.
Now you get the six numbers, or ok if youre a dill it will be ten. But everyone undertands, and someone who doesnt understand wont have picked out the wrong numerals.

You guys picking out significant red numbers at your desk.
Times of stress, make it easy. Hell even the yanks understand it.
Ill respond properly later . Honestly its beer oclock.

[neilmny]

.......................So, where does the 6 digit reference come from? 54H 671880 5871675 = 718 716. BTW, the UTM grid is measured in metres so 671675 is 5 metres from 671670.

I'm a bit confused here bernieq, not that that's anything new.
Refering to your co ordinates 54H 671880 5871675 did you mean the difference between 54H 671880 5871675 and 54H 671880 587167O is 5 metres?
In terms of shortened UTM references I believe the difference between 671675 and 671670 is 500 metres.

[tastrax]

Hi Rob,

I agree that each grid reference system has the ability to give a true and correct location however its ONLY true and correct if it contains all the detail. Even a full 13 figure reference (with just the numbers) is repeated again and again across the globe so the important thing is the full detail.

[Zone-5]

Just goes to prove that the Garmin 62s can do it all if you live long enough to figure it out!!!!

After being so confused for so long, I'm now somewhat relieved that the money I spent for my Etrex was not a complete waste since nobody else seems to know how to use it either!



When I'm in doubt I go here for my answers, sort of..

http://www.gpsinformation.org/dale/wgarmin.htm

[weeds]

Well the smallest numbers on that screen are the eastings and northings.
Dont worry, on mine its worse. I had a colorado and oregon to trial but there were a few things I didnt like about em.
The idea of having MGRS is that five numbers are displayed, you discount the last two.
It lessens the chance of glance misreading, or picking out the middle of the numberset in the rain.

All my topos "effectively" have mgrs. Its a position format. Datum is still datum, WGS84, GDA94, whatever.
Ive yet to meet anyone without a ruler, calculator and pencil who can work things out in the bush using degrees minutes and seconds.
Ive seen people try to split degrees on a terrestrial map. Not a pretty sight.
Ill use decimal degrees outside in the ocean. No problems. Charts dont display grids.

1.jpg

2.jpg

3.jpg

Not sure if Rob is still about........thanks for the helpful post.

I assume when I put a six figure grid in I just leave the last two digits as zero??......as there is room for ten

Cheers

[weeds]

Off course it zeros.......