Navigation Formats

Submitted: Monday, Jan 10, 2011 at 20:58
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Hello,
A couple of yeras ago on a hunting trip a friend of mine who is ex military showed me how to navigate on a map using co-ordinates on a GPS. He showed me the Northings and Eastings format, which upon searching here is apparantly called the UTM format. With that system and the correct map (I usually use the NSW gov topos) I can accurately tell where I am at any given time.
I have recently purchased the Ron And Viv Moon Cape york book, and all co-ordinates seem to be in a longitude and lattitude format, which I do not know how to use. I will buy a proper topographic map for the area before I go, which should have the UTM numbers that I know, but my question is, is it a good idea to learn to use this longitude and lattitude format before I head off? I'm not asking for lessons, just whether I should learn.
Also, is there one topo for the tip, or will I have to get a stack? want to be covered for the CREB track and the OTL.

Cheers Chris.

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Reply By: Ruffy-Dan - Monday, Jan 10, 2011 at 22:20

Monday, Jan 10, 2011 at 22:20
Unfortunately you will have to learn. UTM is slightly less accurate as it makes a the round earth flat. I'm talking centimetres.... However UTM is so, so, so much more simple but not recognised world wide.
Lat long is recognised by every body every where so you'll find it appears in most print mediums.
Lat long is not hard to learn, same principles, you just can't define any one number as a particular distance.
Robert Pepper has two great books on navigation.

Dan
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Follow Up By: The Explorer - Monday, Jan 10, 2011 at 23:45

Monday, Jan 10, 2011 at 23:45
Hi

Think you are confusing the accuracy of the representation of the earth’s surface with the accuracy of coordinates. My understanding is that UTM was developed to improve the accuracy of measurements – hence it widespread use for this purpose. UTM coordinates can be used to locate (and subsequently re-locate) any point to sub-millimetre accuracy.
Totally irrelevant for this discussion anyway as when scaling off a 250K, 100K, 50K or 25K paper map, accuracy will be governed by the scale of the map. For example, a thin pencil line on a 25K map is at least 10m wide! The Natmap 250K raster maps that many people find more than useful shows the average highway defined by a ~250m wide red line!

Cheers
Greg


I sent one final shout after him to stick to the track, to which he replied “All right,” That was the last ever seen of Gibson - E Giles 23 April 1874

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Follow Up By: WBS - Tuesday, Jan 11, 2011 at 19:08

Tuesday, Jan 11, 2011 at 19:08
Tanka
You can convert Lat & Long to UTM on the Geoscience Australia Web site among others. UTM is easier to use on a paper map because you can measure distance with a ruler and use the grids as a reference.

If you have a topo map you should be able to measure both UTM (Grid Coordinates) and lats & longs. All topo maps I've ever seen have both sets of coordinates.

I don't know about UTM being less accurate than latitude and Longitude it is just a different system and not universal.
WBS
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Follow Up By: Bazooka - Tuesday, Jan 11, 2011 at 22:22

Tuesday, Jan 11, 2011 at 22:22
A few points:
1) The conversion from lat/long to UTM and vice versa applies to UTM projection maps/coordinates with the same datum.
2) UTM is indeed a 'universal' projection/coord system.
3) Distance can be measured on any map with a scale (yes it is easier on a UTM map with gridlines).
4) Any decent GPS with a digital mapping product can calculate distances using lat/long coords, or along a route.
5) Accuracy is dependent on many things including map projections, scales, GPS quality and satellte signal availability.
5)UTM is rarely, if ever, used for small scale maps (1:500K ans smaller), hence you will not find UTM coords on them.
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Follow Up By: Robin Miller - Wednesday, Jan 12, 2011 at 13:50

Wednesday, Jan 12, 2011 at 13:50
Hi Bazooka

Not sure if you meant point 5 , its the other way round a lot, UTM is the system used on our best 4wd track maps like the Rooftop series which is all 1:100k and below.
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Follow Up By: The Explorer - Wednesday, Jan 12, 2011 at 14:02

Wednesday, Jan 12, 2011 at 14:02
Robin

You have confused the terminology - small scale maps are 250K, 500K, 1:1Million etc. The term small scale refers to the scale of objects depicted on the maps e.g. buildings will appear "small" on a 500K or greater map.

The term "large" scale refers to maps where objects are larger e.g. 100K, 50K, 25K etc etc.

It is a relative term though so you can say a 500K map is a larger scale than a 1:1Mill scale map or that a 50K map is smaller scale than a 25K map.

The reason that UTM is not generally used on smaller scale maps is because they generally cover more than one zone - different zones have different projections. Among other things it would be rather difficult to have the coordinates of two different zones printed around the boundary of the map.

Cheers
Greg
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Follow Up By: Bazooka - Wednesday, Jan 12, 2011 at 15:14

Wednesday, Jan 12, 2011 at 15:14
Okay, getting into the technical now.

"different zones have different projections."
Greg, assume you mean '...have different (false) origins' (not that this means anything to most people).

I would also add to your last par - the larger the area covered the greater the distortion/inaccuracy (eg scale) of the projection, but that is neither understood nor a particular concern for 'amateur' users.
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Robin - the terminology wrt scale is commonly misunderstood, as Greg has rightly pointed out. The simple way to think about scale is the larger the number the smaller the scale. Alternatively, view the numbers as a fraction eg 1:100,000=1/100,000, which is a LARGER number than say 1/500,000.
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On consideration I would have a minor concern about an 'amateur' reporting his position using UTM grid coords, since those coords are (generally) not unique unless accompanied by a zone number. Reporting the full northing/easting would also be difficult for some people unfamiliar with UTM.
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Follow Up By: The Explorer - Wednesday, Jan 12, 2011 at 15:45

Wednesday, Jan 12, 2011 at 15:45
I suppose by the simplest definition all the UTM zones are the same projection. So yes what I meant was, going one step further is that that each zone uses different false origins AND different Central Meridians...so there is not one single UTM projection but many based on the numbers you enter - they are all indeed UTM projection ..but all 60 are different.

Cheers
Greg
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Follow Up By: The Explorer - Wednesday, Jan 12, 2011 at 15:54

Wednesday, Jan 12, 2011 at 15:54
"Reporting the full northing/easting would also be difficult for some people unfamiliar with UTM."

Same issues can arise with Lat/Long.

I was asked by someone to plot this co-ord on a map the other day .....

115°40' 87"

and this

32°46' 78"

:)

Cheers
Greg
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Follow Up By: Robin Miller - Wednesday, Jan 12, 2011 at 16:29

Wednesday, Jan 12, 2011 at 16:29
Hi Guys

Yep I agree its a terminology issue and needs an explanation (hence term ratio which is explicit) , and UTM generally cuts off maps basically when you can't have meaningful 1km squares

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Follow Up By: Bazooka - Wednesday, Jan 12, 2011 at 20:01

Wednesday, Jan 12, 2011 at 20:01
Greg
Was he surprised when you handed him two lines (for each)? Obviously a one dimensional character!

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Follow Up By: The Explorer - Wednesday, Jan 12, 2011 at 20:21

Wednesday, Jan 12, 2011 at 20:21
Sorry, should have posted both lat and long in each case...think I have confused you.....look at the seconds in each example.

Cheers
Greg
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Follow Up By: Bazooka - Wednesday, Jan 12, 2011 at 21:37

Wednesday, Jan 12, 2011 at 21:37
Failing eyesight! He was probably thinking of the 'new decimal system', 100''=1 minute etc
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Follow Up By: The Explorer - Thursday, Jan 13, 2011 at 00:16

Thursday, Jan 13, 2011 at 00:16
Yes - but it becomes a guessing game as the minutes maybe decimal as well?

Just an example of how coords in any format can be confused by simple misinterpretations. My point - neither UTM or lat/long are immune from people passing on wrong data in either format. Base on experience can’t say which one is likely to result in less problems. Its not rocket science and you don’t need to know or understand all the theory behind coordinates and projections (I don’t obviously)...but if you get full bottle on the basics on one or the other (i.e. lat/long or UTM or both) should not be a problem.

Cheers
Greg
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Reply By: Bazooka - Monday, Jan 10, 2011 at 23:30

Monday, Jan 10, 2011 at 23:30
Chris
UTM, with its 6 degree zones, false origins for each zone, and non-unique coordinate values (unless a zone number is appended), is a relatively complex system so if you can understand that you will have little trouble with lat/long.

The UTM projection/coord system, which is recognised worldwide and used in many countries for 'large scale' (eg 1:100,000) topo mapping, is great for a range of applications but for simple navigation it is overkill. UTM GRID coords are easily read off many maps because the UTM grid is plotted at close intervals (1km on 100K maps), whereas on most maps very few lines of latitude and longitude (known as the 'graticule') are plotted. If, for example every 1' of latitude and longitude was plotted on a map then it would be simple to read off the lat/long coords fairly accurately.

By the way, if the Moon book uses the standard Australian datum (GDA94 or its equivalent WGS84) then the lats and longs in the book will be the same as the lats and longs on your modern topo maps (and will be very close even if your topo maps are based on the AGD66/84 datum).
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Reply By: Member - John R (cQld) - Tuesday, Jan 11, 2011 at 10:39

Tuesday, Jan 11, 2011 at 10:39
In answer to your last question, yes you will need more than one topo map for the Cape. At the 1:250,000 scale maps, there are 14 maps to cover the Cape from Cooktown north, though you would probably not use all of these (only a few if you just restrict yourself to maps covering the CREB and OTL tracks). What you need is a guide to topographic maps, so you can see which ones you really want, or alternatively a PC etc with a mapping program.

Cheers, John

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Reply By: Robin Miller - Tuesday, Jan 11, 2011 at 19:58

Tuesday, Jan 11, 2011 at 19:58
UTM is great Chris as it reads out in meters and is the only system where you have a chance of working out distances on the fly - hence we always put eveything in that format if it isn't already.

Whats worth doing is to practise using a program or your GPS to change co-ords settings quickly, i.e. we download plots etc , change settings , and in an instant they are all changed.

A significant issue with lat/long is that different sources use different lat\long
i.e. some use minutes and seconds and others use decimal minutes , some even give the lat/long as decimal degrees.

Seen lots of errors caused by this use , so reccomend just convert all to UTM and aviod confusion.
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Follow Up By: The Explorer - Tuesday, Jan 11, 2011 at 23:06

Tuesday, Jan 11, 2011 at 23:06
"so reccomend just convert all to UTM and aviod confusion."

Seen lots of confusion with UTM as well with people not specifying Zones or Datums. Nothing foolproof with UTM relative to Lat/long though there maybe a few less confusing options. Lat/Long has its advantages - you wont catch any pilots or skippers using UTM.

Cheers
Greg
I sent one final shout after him to stick to the track, to which he replied “All right,” That was the last ever seen of Gibson - E Giles 23 April 1874

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Follow Up By: Robin Miller - Wednesday, Jan 12, 2011 at 13:22

Wednesday, Jan 12, 2011 at 13:22
Hi Greg

For pilots etc they usually move based on a bearing , so its more suitable to say heading 145 etc than to use a utm co-ord which is primarily aimed at point specification and usually accessed by multiple fixed roads.
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Follow Up By: The Explorer - Wednesday, Jan 12, 2011 at 14:18

Wednesday, Jan 12, 2011 at 14:18
? Best way to navigate to any coordinate (lat/long or UTM) in a plane is using a bearing. Obviously if you are in a car its generally easier to use roads:) Both lat/long and UTM are point based. They are both coordinates and can be used for the same purpose. My point about lat/long being used by pilots and skippers was to illustrate that it is obvioulsy not as confusing a some would suggest.

Cheers
Greg
I sent one final shout after him to stick to the track, to which he replied “All right,” That was the last ever seen of Gibson - E Giles 23 April 1874

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Follow Up By: Pete Jackman (SA) - Wednesday, Jan 12, 2011 at 18:43

Wednesday, Jan 12, 2011 at 18:43
Basic rule in the military was that anything interesting was always at the intersection of four topo maps and two UTM grid systems!

I can use both but prefer Lat/Long which is just as easy to gage distance with if you think in nautical miles:

1º = 60 nautical miles
1' = 2000 yards
1" = 33.3 yards


The Natmap 1:250,000 has 1' ticks on it which makes measuring or eye balling distances easy.

Cheers

Pete
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Follow Up By: Robin Miller - Wednesday, Jan 12, 2011 at 19:09

Wednesday, Jan 12, 2011 at 19:09
Hi Pete

That explains why they can't hit anything , with 1 degree of longitude being 69 miles at equator and 49 miles in Tassie the shells keep falling 32km short - better get them onto UTM ASAP.
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Follow Up By: Pete Jackman (SA) - Thursday, Jan 13, 2011 at 09:37

Thursday, Jan 13, 2011 at 09:37
That is why you always measure distances from the longitude scale.
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Follow Up By: Pete Jackman (SA) - Thursday, Jan 13, 2011 at 09:38

Thursday, Jan 13, 2011 at 09:38
Sorry - took my idiot pills this morning - that should have read:

That is why you NEVER measure distances from the longitude scale.

:o)
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Follow Up By: Bazooka - Thursday, Jan 13, 2011 at 10:59

Thursday, Jan 13, 2011 at 10:59
Pete

"That is why you NEVER measure distances from the longitude scale"
Really depends on the map projection, and often map scale. On some projections the scale is only valid ('accurate') along the latitude(s) of origin (ie the prime latitude(s) used to mathematically construct the graticule). For most larger scale Australian topo maps used by Exploroz people it isn't significant as we know.

Mind you I do get a chuckle when people comment about accuracy (which is always a relative measurement anyhow - ie how accurate do you want or need it to be? A surveyor needs cm accuracy, for Joe Blow probably 100+m would suffice). One really needs to understand map projections to make sensible comments on accuracy.

GPS can of course be VERY accurate, primarily because it does not try to represent the earth as a flat sheet. It's all in the maths/geometry.
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Follow Up By: Pete Jackman (SA) - Thursday, Jan 13, 2011 at 12:44

Thursday, Jan 13, 2011 at 12:44
Good comments Bazooka,

I have navigated on Mercator charts where the distortion of that projection meant that there was a significant different between map scale measured at the top and bottom, but these were small scale ocean charts covering 5 to 10º of latitude.

As you note for most maps we are using on the road the scale is sufficiently large that the differences are negligible.

And you are right about accuracy Bazooka. At least most recent maps are printed to the WGS84 datum but it is always worth checking the margins. GPS tells you where you are but if you can't work that back to a map position the information is not all that useful unless you are calling for help.

Cheers

Pete


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Reply By: Member - Tanka (NSW) - Wednesday, Jan 12, 2011 at 17:26

Wednesday, Jan 12, 2011 at 17:26
Thanks everyone for your input. At present, I don't have a fancy GPS, just a B&W handheld one which pretty much just gives me a the co-ordinates for where I am standing. I then use my compass, pencil and ruler to make sure I am still on the road/track/area, that I think I am.
I think I will learn the lat/long stuff, as it's seems to be commonly used, and from comments here I think it would be an advantage to know both.
Perhaps I should also invest in something like a Hema Navigator, so I can tell at a glance whether I am on the correct road or not....

Cheers Tanka.
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Reply By: Sigmund - Friday, Jan 14, 2011 at 07:22

Friday, Jan 14, 2011 at 07:22
There's an online converter here:

http://home.hiwaay.net/~taylorc/toolbox/geography/geoutm.html

and formulae available for Excel etc.

My GPS can display UTM as well as Lat/lon in 3 formats, so I've always assumed I could switch for any diff format coords I wanted to enter manually and then return to the normal position format.
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