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Utm Vs Lat Lon


Cap'n Jack
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Interesting you should mention them - I just had my first brush with UTMs today. Noobie here, and still getting used to lat/lon much less utms. But just today I got (my first ever!) FTF on a multi cache that used UTMs for the first part of the trail.

 

Walking Tour of the Solar System

 

I did a quick bit of research beforehand and learned it's a system that uses meters I believe. I just got back from South Africa so am fairly comfortable with metric, and I must say - I rather liked using the UTMs. Just seemed to make more sense than the lat/lon.

 

A most fun cache, I might add!

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From what I understand, maps are made such that UTM coordinates are linear with respect to the projection, where as latitude and longitude measures are non-linear across the face of a map or from one map to another even at the same scale.

 

The upside to UTM is that offsets can be found with a map by ruler and pencil. Modern GPSr's can output in that format just as easily.

 

The downside is, given a UTM marking on a map, you can't go to http://www.geocaching.com/seek/ with UTM coordinates to see if there are any caches on your map. You'd have to have your GPSr (or calculator) do a conversion so that you can use the search for geocaches.

 

This is of course my interpretation of what I've read. geocaching.com might have that as an advanced feature already, or there may be more to it than just a conversion forumula that prevents them from having UTM entry for finding them.

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You can probably find your location on a topo map to within 50 meters using UTM> So using these maps with your GPS set to showUTM coordinates will then allow you to look at the topo map and spot your location pretty acurately. That's difficult to do with degrees and minutes and seconds or other formats.

 

UTM maps can be bought from US Geodetic Service or sporting store outlets. Or you can purchase software suh as National Geographic Topo which will print the same maps with the UTM grid lines marked in.

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I use both lat/long and UTMs interchangeably and I don't really notice a difference, although with UTMs I can tell how far away I am by looking at the coordinates.

 

I interchange them for just for fun. I recently did a GPS training where the participants did some multi-stage caches I placed, and I switched datums and location formats at each stage. Gave them a chance to learn the setup menu.

 

Didn't really add to the discussion. Sorry.

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You can probably find your location on a topo map to within 50 meters using UTM>  So using these maps with your GPS set to showUTM coordinates will then allow you to look at the topo map and spot your location pretty acurately.  That's difficult to do with degrees and minutes and seconds or other formats.

 

Actually, you can easily plot your location to within about 10 meters using UTM. For instance in the UTM grid of 14S 550123 03854567, plotting it on a map, you would normally ignore the first 5 and the 038 leaving a location of 50123 54567. Ignoring the final 3 digits of both the easting and northing, leaving 50 54, defines a the intersection of a grid 1000x1000 meters. By definition, the given location is somewhere within the square using this intersection as the lower left corner. Adding 1 more digit to both the easting and northing, 501 545, defines a square 100x100. Finally adding another digit to give 4 digits for both easting and northing 5012 5456 results in a square being defined that is 10x10 meters. For all practical purposes, this is about as far as a person can descern on a map. The UTM as displayed on the normal cache page is defining a square 1x1 meter square.

Edited by Team Madog
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You can probably find your location on a topo map to within 50 meters using UTM> So using these maps with your GPS set to showUTM coordinates will then allow you to look at the topo map and spot your location pretty acurately. That's difficult to do with degrees and minutes and seconds or other formats.

 

UTM maps can be bought from US Geodetic Service or sporting store outlets. Or you can purchase software suh as National Geographic Topo which will print the same maps with the UTM grid lines marked in.

With a UTM 10 digit grid you will pinpoint your map within one meter. UTM is the standard system for the US Infantry. I was trained in the Boy Scouts using lat/long I never was comfortable with this system. In the military I used UTM and it made sense. It lays out the earth in a big grid. You can get a protracter from several surplus outlets online that will work with your UTM map. THis will speed up your learning curve.

2cents

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A few months back Backpacker Magazine started printing coordinates for hikes in UTM and they also offer some of those coordinates online.

 

Their tagline: World's First GPS Enabled Magazine

 

I've been a subscriber for a long time and this new feature only adds to my enjoyment.

 

:D:D

I had suscribed to it....great mag and yep I got the issues wiht the coords. Great idea!

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You can probably find your location on a topo map to within 50 meters using UTM>  So using these maps with your GPS set to showUTM coordinates will then allow you to look at the topo map and spot your location pretty acurately.  That's difficult to do with degrees and minutes and seconds or other formats.

 

UTM maps can be bought from US Geodetic Service or sporting store outlets.  Or you can purchase software suh as National Geographic Topo which will print the same maps with the UTM grid lines marked in.

With a UTM 10 digit grid you will pinpoint your map within one meter. UTM is the standard system for the US Infantry. I was trained in the Boy Scouts using lat/long I never was comfortable with this system. In the military I used UTM and it made sense. It lays out the earth in a big grid. You can get a protracter from several surplus outlets online that will work with your UTM map. THis will speed up your learning curve.

2cents

Goods points about the roamer and grids. My post, not clearly stated, was to indicate that just using your eye on a UTM map with only the 1000 meter grids, you can get a quick spotting within 50-100 meters with out any roamer or grid template overlay.

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You can probably find your location on a topo map to within 50 meters using UTM>  So using these maps with your GPS set to showUTM coordinates will then allow you to look at the topo map and spot your location pretty acurately.  That's difficult to do with degrees and minutes and seconds or other formats.

 

UTM maps can be bought from US Geodetic Service or sporting store outlets.  Or you can purchase software suh as National Geographic Topo which will print the same maps with the UTM grid lines marked in.

With a UTM 10 digit grid you will pinpoint your map within one meter. UTM is the standard system for the US Infantry. I was trained in the Boy Scouts using lat/long I never was comfortable with this system. In the military I used UTM and it made sense. It lays out the earth in a big grid. You can get a protracter from several surplus outlets online that will work with your UTM map. THis will speed up your learning curve.

2cents

Goods points about the roamer and grids. My post, not clearly stated, was to indicate that just using your eye on a UTM map with only the 1000 meter grids, you can get a quick spotting within 50-100 meters with out any roamer or grid template overlay.

Absolutely, I understand.

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UTM's....who uses them? The good old British Forces...If I had tried to teach Lat & Long to young 16 year old soldiers, I would still be doing it today....We only really used six figure grids for normal map reading but ten figure grids were used as well.. even four figure grids down to 1sq Kilometer were used to describe an area to recce in or find a Hide for thre night. I think it is much easier to understand and you can tailor the accuracy as you require it. Although 8 and 10 figure grids did get them scratching their heads.

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In the Netherlands (Europe) we have our own local yokel UTM system with the name 'Rijksdriehoeksmeting' mostly elsewhere know as 'Dutch Grid'.

It is metric, uses an offset so no easting/northing misunderstandigs are possible: number <300000 is always the easting >300.000 up to 800000 is northing. Surveyers have to use this coordinate system and all offical documents use them (cadastral f.i.)

Maps available for emergency services have that Dutch grid on them.

Here is an article about: Use of the RD-grid in your GPS

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I agree!!!! UTM is a lot easier to use than Lat/Lon. I belong to a county Search and Rescue unit and all the training we have had and practice we do is in UTM. I do have a question though...... I have gsak and when I do a query and download the data, all I get is the Lat/Lon info, the UTM info isn't there like it is when you look at the cache info online. Any way to get that other than running a conversion program?

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UTM is excellent for anyone who believes that the Earth is flat, since that is how it attempts to represent it. As a result, it is useful when navigating with paper maps, since they are flat, too.

 

But for use with a GPS, UTM is not particularly helpful, since it has several drawbacks. Most notably, UTM north and east are not true north and east. Bearings derived from UTM are incorrect. And UTM only works for relatively short distances.

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I agree!!!! UTM is a lot easier to use than Lat/Lon. I belong to a county Search and Rescue unit and all the training we have had and practice we do is in UTM. I do have a question though...... I have gsak and when I do a query and download the data, all I get is the Lat/Lon info, the UTM info isn't there like it is when you look at the cache info online. Any way to get that other than running a conversion program?

Tools=>Options=>HTML

 

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UTM is excellent for anyone who believes that the Earth is flat, since that is how it attempts to represent it.  As a result, it is useful when navigating with paper maps, since they are flat, too. 

 

But for use with a GPS, UTM  is not particularly helpful, since it has several drawbacks.  Most notably, UTM north and east are not true north and east.  Bearings derived from UTM are incorrect.  And UTM only works for relatively short distances.

well, I wouldnt go so far as saying the world is flat so much as it is faceted :D

 

If one is planning trans-oceanic or trans-continental journies, then I suppose I would have to concede to inadequacies over long distances.

 

There is distortion of one form or another in ALL map projections to one or another degree and that would make either make north NOT 'true north' and East not 'true 'East' or distort apparent distances between distant points.

 

I have not seen any 'bearing' errors while using UTM.. doesnt mean it doesn't exist, just that I havent personally experienced it yet. Would be something I would like to understand

 

The biggest benifit I have derived from UTM is the ease of computing distances between points within each zone ... having to convert the locations from DMS into minutes then remember how many miles in a minute.. how many feet in a mile.then pump it all through the Distance=sqrt(((x2-x1)squared)+(y1-y2)squared)) then convert it all back up to the appropriate distance units

 

UTM is simple, every thing pumps right through the equation without any conversions and out comes distance in meters. Of course, if you want imperial units, you still have to do intermediate conversions

 

I still belive that, with all other things being equal, UTM is still more precise than lat/lon ( 3.3 feet=39in.=1.25yards) than lat/lon in Dec. Min (.001min=5.28ft) , more or less depoending of course on latitude :lol:

 

click for more on UTM&GPS

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In the Netherlands (Europe) we have our own local yokel UTM system with the name 'Rijksdriehoeksmeting' mostly elsewhere know as 'Dutch Grid'.

[/url]

 

If it's local, it's not UTM. UTM stands for Universal Transverse Mercator. It's a map projection system in which the world (except the polar regions) is divided into 60 zones, each 6 degrees wide. Each zone is mapped with a Transverse Mercator projection with the middle meridian of the zone as central meridian. The other projection parameters are the same for all zones.

 

Many countries have local Transverse Mercator projections with their own set of parameters, but these projections are not UTM, because UTM cannot be redefined.

 

Btw, this also means that the "User UTM grid" you can define in some Garmin units is nonsense. If it's user defined it's not UTM.

 

haraldn

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UTM is excellent for anyone who believes that the Earth is flat, since that is how it attempts to represent it.  As a result, it is useful when navigating with paper maps, since they are flat, too. 

 

But for use with a GPS, UTM  is not particularly helpful, since it has several drawbacks.  Most notably, UTM north and east are not true north and east.  Bearings derived from UTM are incorrect.  And UTM only works for relatively short distances.

Well, geodetic coordinates attempt to represent the Earth as a sphere, which it isn't either. UTM doesn't represent the earth as flat. It represents a six degrees wide section of the Earth as flat. UTM surely doesn't work for navigating across oceans, but navigating round a cache is usually short distance, so UTM works well. The only exception would be if the cahce is close to a zone border.

 

Magnetic compasses don't point to true north either, so bearings taken with a magnetic compass have to be corrected. It's no problem to include the meridian convergence (difference between grid north and true north) in the correction. Some maps actually state magnetic variation relative to grid north so you can do it all in one operation.

 

haraldn

Edited by haraldn
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Well, geodetic coordinates attempt to represent the Earth as a sphere, which it isn't either.

The above is not true. Completely false. The lat/long coordinate system does not approximate the Earth as a sphere. It doesn't approximate the Earth as anything. That's why it is an approriate coordinate system.

 

UTM is not a coordinate system in the same sense; it is based upon a projection.

 

I knew I should have stayed out of the religious part of the forums.

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In the Netherlands (Europe) we have our own local yokel UTM system with the name 'Rijksdriehoeksmeting' mostly elsewhere know as 'Dutch Grid'.

[/url]

 

If it's local, it's not UTM.

[...]

haraldn

It sure is not. I only mentioned it so because the use of metric coordinates is the same a bit.

The differences are:

Dutch topographic maps are projected from the Bessel 1841 ellipsoid by way of the double projection according to Mr. Schreiber. That is not a transverse Mercator projection. So there is also no central meridian or something but a point only. In the centre of the country.

Because our country is a bit square in form it is logically sound to have a projection where all things that go 'wrong' when projecting from something round to a flat surface are equally distributed in all directions.

In this case the mapdatum and the projection 'belong' to each other; when using Dutch grid you alway have to use the Bessel mapdatum.

 

UTM can combine with every mapdatum you wish. Nowadays modern maps younger than 1984 can use WGS84, older maps in Europe may use ED50 or the locally used mapdatum.

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Well fizzymagic, I wonder who's religous. We're discussing the pros and cons with variuos coordinate systems here. Both virgo91967 and I wrote that geodetic coordinates are the best for large areas, while UTM (or for that matter, coordinates based upon other projections such as Lambert Conformal Conical) may be better when working with small areas. You seem to think there is no god besides lat/long, hallelujah.

 

Of course, UTM cannot be used for the GPS system, but geodetic coordinates cannot either. The system uses a three-dimensional cartesian coordinate system. The position (X.Y,Z) of the receiver in that system is computed and then converted to latitude, longitude and ellipsoid height. Some receivers also have a geoid height model, so they can compute height above mean sea level from the ellipsoid height.

 

Images of the Earth or part of it on a map are always projections, so if you work with maps you must use a projection. Mapping GPSrs also use projections. Otherwise they wouldn't be able to map things to the correct pixels. Lat/long are good for long distance navigation especially if you use celestial navigation. For describing small areas, rectangular coordinates are much better. I suppose, even you wouldn't describe your house or your garden in lat/long.

 

world.gif

 

The best picture of the Earth?

Edited by haraldn
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Actually , the earth is not a true sphere, but an 'oblate spheroid' its radius at the equator is aseveral miles more than its radius at either pole. I suppose that is why the metric system unit of length is determined by distance from the north pole rather than as a fraction of the equator???

 

I do know that the US Coast Guard (keep up the good work ouys and girls) still requires learning and demonstrating the ability to plot a fix according to charts, dead reckoning, time and sextant as well as gps.

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While I'm quite happy to use lat/lon for caching purposes, the main advantage to me of having some familiarity with UTM was that I could use it to look up the rough address os a waypoint using my standard street directory (map book / A-Z / whatever you call it where you live!)

 

This has been somewhat superceded by laptops and maps on my Palm PDA, but it got us to the general vicinity of several waypoints of multicaches in the past!

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