UTM vs. LAT/LON

[KD7EAV]

I notice that all coordinates given for caches are in the hddd mm.mmm format. I have found that UTM and a 1,000 meter grid are much faster and easier to work with than lat/lon. The SAR team I worked with used UTM for everything except giving coordinates to helocopters. Am I the only one, or are there other proponents of UTM lurking in the shadows?

[Growley]

KD7EAV,

This has been discussed in the past and there are some other threads on the subject. You might want to try the search feature to locate them. Just about 10 days ago my office was involved in the removal of a military helicopter that had crashed nearby. We were trying to get a location when someone walked into the office with the coordinates in MGRS. I quickly entered them into my trusty Garmin 76S and we had the location in seconds. As a former Marine I am used to these different datums (somewhat). However, I am always interested in learning different (and hopefully) easier ways of pin pointing my location. Perhaps you will get another discussion going here.

[+shawhh]

for land nav i certainly agree that utm/mgrs is the more user friendly format, esp. since many usgs and all dod maps are grided for utm/mgrs. sure to catch on if more people learn the system.

[+Jumpmaster]

quote:

---

Just about 10 days ago my office was involved in the removal of a military helicopter that had crashed nearby. We were trying to get a location when someone walked into the office with the coordinates in MGRS. I quickly entered them into my trusty Garmin 76S and we had the location in seconds. As a former Marine I am used to these different datums (somewhat). However, I am always interested in learning different (and hopefully) easier ways of pin pointing my location.

---

 

Not to pick nits, but a datum is not the same thing as a coordinate system. For some reason or another, the two are thrown around as interchangable but they are not the same thing.

 

Coordinate system: i.e. MGRS, UTM, LAT/LON

Datum: i.e NAD27, WGS84, NAD83

 

FWIW, I also hope people will take to using UTM coordinates and learn the system. I personally find it easier to use.

 

Cheers!

 

JM-99

[+mrp]

I think the primary reason for using the H DDD MM.MMM coordinate format and the WGS84 datum is becuase most GPSRs come configured for them out of the box. We already have enough questions from newbies about entering coordnates and converting formats without making it more complicated for them. If you prefer UTM, there are dozens of utilities out there that will do the conversion for you (most of them free).

 

-- Mitch

[+unclerojelio]

There is even a button on the cache description page that will give do the UTM conversion for you.

 

... Two roads diverged in a wood, and I--

I took the one less traveled by, ...

 

unclerojelio

[+unclerojelio]

There is even a button on the cache description page that will give do the UTM conversion for you.

 

... Two roads diverged in a wood, and I--

I took the one less traveled by, ...

 

unclerojelio

[+Jumpmaster]

What I was trying to say was that I wish people (in general...not just in geocaching) weren't so adverse to learning the UTM system, my students included.

 

I have a lot of friends that are also gadget freaks like myself. They refuse to switch their GPS's from Lat/Lon to UTM because, "Lat/Lon is more intuitive" or for whatever reason. Oh well, to each his own!

 

I don't generally use the conversion tool on the cache page...I usually just enter it in in Lat/Lon and reset my GPS to back UTM. If I have a lot of waypoints to enter, I let the GPS programming software do the conversions.

 

JM-99

[+Jumpmaster]

What I was trying to say was that I wish people (in general...not just in geocaching) weren't so adverse to learning the UTM system, my students included.

 

I have a lot of friends that are also gadget freaks like myself. They refuse to switch their GPS's from Lat/Lon to UTM because, "Lat/Lon is more intuitive" or for whatever reason. Oh well, to each his own!

 

I don't generally use the conversion tool on the cache page...I usually just enter it in in Lat/Lon and reset my GPS to back UTM. If I have a lot of waypoints to enter, I let the GPS programming software do the conversions.

 

JM-99

[+infosponge]

With Lat/Lon I can visualize how it works in my head...UTM...makes my brain hurt.

 

I imagine if I used printed maps a lot it would be worthwhile for me, but usually I'm using the map built into my Meridian and/or a topo/aerial I've printed out of ExpertGPS or Manifold for general reference.

[+infosponge]

With Lat/Lon I can visualize how it works in my head...UTM...makes my brain hurt.

 

I imagine if I used printed maps a lot it would be worthwhile for me, but usually I'm using the map built into my Meridian and/or a topo/aerial I've printed out of ExpertGPS or Manifold for general reference.

[Kerry.]

quote:

---

Originally posted by Pneumatic:

I think the primary reason for using the H DDD MM.MMM coordinate format and the WGS84 datum is becuase most GPSRs come configured for them out of the box.

---

 

WGS84 is an earth centred datum, the same reference GPS is based on and hence to a GPS receiver is a zero transformation. All other datum's generally require some approximation and tend to make life awkard but back then things were based on the best information at the time.

 

One day there might only be 1 datum, that will be a good day.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

quote:

---

Originally posted by Pneumatic:

I think the primary reason for using the H DDD MM.MMM coordinate format and the WGS84 datum is becuase most GPSRs come configured for them out of the box.

---

 

WGS84 is an earth centred datum, the same reference GPS is based on and hence to a GPS receiver is a zero transformation. All other datum's generally require some approximation and tend to make life awkard but back then things were based on the best information at the time.

 

One day there might only be 1 datum, that will be a good day.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+Alan2]

Kery: If we know the conversion factor when switching from Nad 27 quads to NAD84, why doesn't the USGS just produced printed mapes with the coordinate system lines updated to the latest Datum?

 

Tks Alan

[+Alan2]

Kery: If we know the conversion factor when switching from Nad 27 quads to NAD84, why doesn't the USGS just produced printed mapes with the coordinate system lines updated to the latest Datum?

 

Tks Alan

[mdmax371]

Were can you buy mercator maps with or without the grid lines?

[Kerry.]

quote:

---

Originally posted by Alan2:

Kery: If we know the conversion factor when switching from Nad 27 quads to NAD84, why doesn't the USGS just produced printed mapes with the coordinate system lines updated to the latest Datum?

Tks Alan

---

 

Alan, in time I imagine that will be the ultimate goal but these things do take time and $$'s. Australia has been on this type of project since the early 90's and is still on going even though the original data was reasonably good compared to other countries.

 

One of the problems in the U.S is some of the NAD27 data is spread over many many years of differing data quality and simply converting bad NAD27 data simply ends up with bad NAD83 data.

That's one reason why some GPS receivers have something like 11 "different" conversions for NAD27.

 

Really with the availability of modern navigation and positioning the oportunity is there to update maps with respect to the accuracy of the navigation systems currently available.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

quote:

---

Originally posted by Alan2:

Kery: If we know the conversion factor when switching from Nad 27 quads to NAD84, why doesn't the USGS just produced printed mapes with the coordinate system lines updated to the latest Datum?

Tks Alan

---

 

Alan, in time I imagine that will be the ultimate goal but these things do take time and $$'s. Australia has been on this type of project since the early 90's and is still on going even though the original data was reasonably good compared to other countries.

 

One of the problems in the U.S is some of the NAD27 data is spread over many many years of differing data quality and simply converting bad NAD27 data simply ends up with bad NAD83 data.

That's one reason why some GPS receivers have something like 11 "different" conversions for NAD27.

 

Really with the availability of modern navigation and positioning the oportunity is there to update maps with respect to the accuracy of the navigation systems currently available.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+Alan2]

Tks Kerry. I knew it seemed too easy.

 

Mdmax371-you cann get 7.5 quads from the US geodetic Service for about US$4.00 or a little more and faster from private services. check the web. UTM lines come on some of these. Where they don't you can draw them in with a good art pen with waterproof archival ink, use .3mm. Check art supply stores. They're throw away type about $3 each.

 

Alan

[+mrcpu]

I was in the military and I prefer UTM and more specifically MGRS ( a subset of UTM).

 

What I'd love to see is an option in my prefs that lets me chose the default coordinate system to display in.

 

Cheers,

 

Rob

Mobile Cache Command

[KD7EAV]

posted by mrcpu:

 

What I'd love to see is an option in my prefs that lets me chose the default coordinate system to display in.

 

*Couldn't have wished for more. It seems that many of the responses to this thread, and possibly a simple majority, are in favor of using UTM for ground navigation. The question now would be to address the feasability of, as mrcpu suggests, "an option in my prefs". As it is now, even if personal choice is UTM, the conversion must be made to hddd mm.mmm format to post anything on the web site. The geocache network is already a great database. Is it possible to make it - gasp- even better?

[Kerry.]

If there's a requirement for a pref option then the underlining coordinate system should be earth centred cartesian . At least that's something that's unique from which ALL other "things" are derived.

 

But basically all have some form of disadvantage, even UTM having that added zone variable and especially when zone to zone transformations or zone overlaps are concerned.

 

It what one gets "more used to" that appears "more friendly" but really they all have some down sides.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

If there's a requirement for a pref option then the underlining coordinate system should be earth centred cartesian . At least that's something that's unique from which ALL other "things" are derived.

 

But basically all have some form of disadvantage, even UTM having that added zone variable and especially when zone to zone transformations or zone overlaps are concerned.

 

It what one gets "more used to" that appears "more friendly" but really they all have some down sides.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Growley]

Jumpmaster, first thanks for pointing out my error in terminology. Something didn't look right when I typed it, but I couldn't place it. Here's my question; If you don't usually use a topo map along with your gps while caching (other than maybe a single page printed from ExpertGPS, etc.) what will the benefit of using UTM or MGRS be?

[+mrcpu]

quote:

---

Originally posted by Growley:

Jumpmaster, first thanks for pointing out my error in terminology. Something didn't look right when I typed it, but I couldn't place it. Here's my question; If you don't usually use a topo map along with your gps while caching (other than maybe a single page printed from ExpertGPS, etc.) what will the benefit of using UTM or MGRS be?

---

 

That's an easy one... if I'm looking for a cache, during that last 50m it is a bit of a zigzag if you follow the arrow, however if you look at the cache location in UTM or MGRS and then your current location in the same format, you can easily move North 34m and then East 12m or whatever it is until you are standing at the waypoint location.

 

On another note, my buddy servman is using a Maggy 310. In D M.mmm format he doesn't have that last decimal point, more like D M.mm HOWEVER in UTM he has the full precision down to the metre.

 

Rob

Mobile Cache Command

[+servman]

I have an older Magellan 310 which only allows DDMMSS or DDMM.MM as options for Lat/Long coordinates. Therefore if I use the DDMM.MMM format the site gives me I introduce up to 10m error just from my rounding. At least when I convert to UTM I know that the coordinates I've entered are within 1m of what the cache hider had on his/her GPS.

 

Ian

Mobile Cache Command

[+mrp]

As with others, I find lat/long to be more intuitive on a global scale. If I see N 32 and W 71, I pretty much know it's in the southeastern US (probably florida or georgia), and if I see N 51 and E 1 I know it's on the coast of england. (or near there). For UTM I have to remember where the meridian for sector 10S is.

 

Where I find UTM very useful is for mathematical manipulation of or coordinates in a local area. There are a number of puzzle caches around here that require some math, and UTM allows for a (roughly) cartesian coordinate system. It's safe to assume that the earth is "flat" for a 20 or 30 mile radius.

 

MrCPU, your example of 32m north and 54m east only works if you know where true north is. If I get my GPSr to tell me 150ft (or 43m) at a bearing of 52 degrees magnetic, then I can just use a compass and some simple distance reckoning to get a good location for the cache.

 

-- Mitch

[+Waterboy]

For those cachers who believe in UTM:

Please calculate the distances between these two caches:

17 T 745870 4721477

18 T 255924 4718312

You may use paper, your head, or a simple calculator. (Calculator may have trig functions.) This must be done without converting to Latitude and Longitude.

 

For the cachers who believe in Lat/Lon:

Please calculate the distances between these two caches:

N 42° 36.392 W 078° 00.160

N 42° 34.718 W 077° 58.448

You may use paper, your head, or a simple calculator. (Calculator may have trig functions.) This must be done without converting to UTM.

 

The two caches actually exist.

[+The Leprechauns]

I am a newbie. I was told that there would be no math. I was told that the only skills necessary for geocaching are an ability to identify Tupperware variants, to classify Happy Meal Toys by their ad campaign, and to see through tree stumps.

 

Seriously... THANKS for the education in this and other threads on map and datum and coordinate systems, this is interesting reading and is digging up brain cells unused since my Boy Scout orienteering days in the 1970's. Much appreciated. And it beats reading the trust agreements sitting on my desk.

 

x-x-x-x-x-x-x-x-x-

"Next time, instead of getting married, I think I'll just find a woman I don't like and buy her a house."

[jfitzpat]

I suppose that one reason not to use UTM in a database like geocaching.com is that it does not cover the entire globe. There is a different metric system for use at the poles.

 

-jjf

[Kerry.]

quote:

---

Originally posted by Waterboy:

For those cachers who believe in UTM:

Please calculate the distances between these two caches:

17 T 745870 4721477

18 T 255924 4718312

You may use paper, your head, or a simple calculator. (Calculator may have trig functions.) This must be done without converting to Latitude and Longitude.

 

For the cachers who believe in Lat/Lon:

Please calculate the distances between these two caches:

N 42° 36.392 W 078° 00.160

N 42° 34.718 W 077° 58.448

You may use paper, your head, or a simple calculator. (Calculator may have trig functions.) This must be done without converting to UTM.

 

The two caches actually exist.

---

 

Datum (assume WGS84 ) and to what type of precision Head, paper or "simple calculator" no matter what way one looks at positions like this in general the result is always going to be a "bit rough", because no one is going to come with something like 3884.401m or 3884.607m and expect somebody to believe "that's it" 3 decimal places and all based on coords to 1m and minutes to 3 decimals etc.

 

Anyway they are presumably the same points with some human "rounding" limitations.

 

Even these 2 points have some rounding issues but then are they 2 points or the same point

 

17 T 745870.000 4721477.000

18 T 253691.750 4721492.548

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

quote:

---

Originally posted by Waterboy:

For those cachers who believe in UTM:

Please calculate the distances between these two caches:

17 T 745870 4721477

18 T 255924 4718312

You may use paper, your head, or a simple calculator. (Calculator may have trig functions.) This must be done without converting to Latitude and Longitude.

 

For the cachers who believe in Lat/Lon:

Please calculate the distances between these two caches:

N 42° 36.392 W 078° 00.160

N 42° 34.718 W 077° 58.448

You may use paper, your head, or a simple calculator. (Calculator may have trig functions.) This must be done without converting to UTM.

 

The two caches actually exist.

---

 

Datum (assume WGS84 ) and to what type of precision Head, paper or "simple calculator" no matter what way one looks at positions like this in general the result is always going to be a "bit rough", because no one is going to come with something like 3884.401m or 3884.607m and expect somebody to believe "that's it" 3 decimal places and all based on coords to 1m and minutes to 3 decimals etc.

 

Anyway they are presumably the same points with some human "rounding" limitations.

 

Even these 2 points have some rounding issues but then are they 2 points or the same point

 

17 T 745870.000 4721477.000

18 T 253691.750 4721492.548

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+mrcpu]

quote:

---

Originally posted by Pneumatic:

 

MrCPU, your example of 32m north and 54m east only works if you know where true north is. If I get my GPSr to tell me 150ft (or 43m) at a bearing of 52 degrees magnetic, then I can just use a compass and some simple distance reckoning to get a good location for the cache.

 

-- Mitch

---

 

What? I don't use my compass for this. That's the point. I look at my current location and head in one direction watching the utm. If N goes the wrong way and E goes the right way (increases or decreases) then I change my direction of travel.

 

Besides, If you go into the settings for your heading you can set that to true or magnetic. If you set it to magenetic it tells you your declination which you can use to adjust your compass.

 

Rob

Mobile Cache Command

[+Waterboy]

For Kerry.

 

I entered the question for one purpose. Thank you for the response. I did not expect the response you sent.

1. You are right, 17 T 745870.000 4721477.000 and 18 T 253691.750 4721492.548 are the same point, or at least within 3 meters of the same point.

2. I am curious how you calculated the value of 18 T 253691.750 4721492.548. Could you list the equations you use.

3. Now to explain the 2 ½ or 3 meters difference. Let’s take a look at the original positions stated.

 

N 42° 36.392 W 078° 00.160 and 17 T 745870 4721477 are identical

 

N 42° 34.718 W 077° 58.448 and 18 T 255924 4718312 are identical

 

They are right on the extreme edge of two UTM zones. Lets rotate these positions three degrees east, to place them right smack in the center of UTM zone 18.

 

N 42° 36.392 W 075° 00.160 or 18 T 499781 4717104

 

N 42° 34.718 W 074° 58.448 or 18 T 502122 4714024

 

4. If you use the two Lat/Long positions the distances around 78° and 75° Longitude are the same. Not so if you use UTM. Also if you calculate a bearing the between point there are problems.

5. The purpose of this exercise is to demonstrate an inaccuracy in one system. Lat/Long is a round earth (spheroid) solution, and the more accurate and consistent.

6. UTM is definitely easier to work with, but it is a flat earth solution. The inaccuracy demonstrated will not effect geocaching activities, or at least how geocaching is performed now.

[+ApK]

quote:

---

I am a newbie. I was told that there would be no math. I was told that the only skills necessary for geocaching are an ability to identify Tupperware variants, to classify Happy Meal Toys by their ad campaign, and to see through tree stumps.

---

That's great! I need to steal that.

 

To the folks who gave reasons for using UTM vs. LatLon without a map, ie looking at the numbers for the last few yards, I don't get it...I do the same with LatLon.

[+ApK]

quote:

---

I am a newbie. I was told that there would be no math. I was told that the only skills necessary for geocaching are an ability to identify Tupperware variants, to classify Happy Meal Toys by their ad campaign, and to see through tree stumps.

---

That's great! I need to steal that.

 

To the folks who gave reasons for using UTM vs. LatLon without a map, ie looking at the numbers for the last few yards, I don't get it...I do the same with LatLon.

[+sbell111]

I have a headache. I think I'll keep using whatever my GSPr and the website use.

[+majicman]

OK,

 

I just finished reading this thread, and I thought I would check everyone's math. I hooked my GPS up to my computer and called Albert Einstein up and asked him to come over and help me plug the numbers in.

 

I HOPE YOU ALL ARE HAPPY! Albert's in the assylum, my computer says, "This computer is stoned!" and my GPS ran down the road screamin', "I can't take it! I can't takkeee iiiiiittttt..." and got runded over by a stupid Dolese Cement truck!

 

Dang, I'm madder 'n a wet hornet and worrieder that a long-tailed pussy-cat on a porch full o' rockin' chairs!

 

--majicman

 

(Always trade UP in both quantity and quality and Geocaches will be both self-sustaining and self-improving!)

[Kerry.]

Waterboy,

 

Really what this has highlighted is the precision (or is the lack of ) that depending on the software/hardware available we are restricted to.

 

With reference to your point 1. 3 metres (or 0.001') is about all most recreational GPSr's are good for. Those coordinates to 3 decimal of a metre (1mm) are exactly that less than 1mm but no normal GPSr's would be able to determine that.

 

2. equations rather long and something a simple calulator simply doesn't/can't handle and are quite extensive.

 

And really for all purposes here the precision is fine but in reality the "actual" UTM coordinates of N42 36.392000' W078 00.160000' are 745870.320mE, 4721478.212mN and N42 34.718' W077 58.448' are 255923.968mE, 4718312.628mN so what appears identical is normally not really identical but the best a particlar system can do.

 

As mentioned previosly both Lat/Long and UTM are both derived from a higher native position format and really both can/will give the same results taking into account coordinate precision, rounding and all that type of stuff.

 

Much like saying what's the direction bewteen 2 points , is that a true bearing, a grid bearing or do they mean an azimuth , similar with distance, Spheroidal, Grid or Plane all of which can be derived from either type of coordinate format and relative to the precision of the available coordinates.

 

Of course not all that important with Geocaching unless one wnats to specificy either end of a match (as well as a dozen separate points in between)

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

Waterboy,

 

Really what this has highlighted is the precision (or is the lack of ) that depending on the software/hardware available we are restricted to.

 

With reference to your point 1. 3 metres (or 0.001') is about all most recreational GPSr's are good for. Those coordinates to 3 decimal of a metre (1mm) are exactly that less than 1mm but no normal GPSr's would be able to determine that.

 

2. equations rather long and something a simple calulator simply doesn't/can't handle and are quite extensive.

 

And really for all purposes here the precision is fine but in reality the "actual" UTM coordinates of N42 36.392000' W078 00.160000' are 745870.320mE, 4721478.212mN and N42 34.718' W077 58.448' are 255923.968mE, 4718312.628mN so what appears identical is normally not really identical but the best a particlar system can do.

 

As mentioned previosly both Lat/Long and UTM are both derived from a higher native position format and really both can/will give the same results taking into account coordinate precision, rounding and all that type of stuff.

 

Much like saying what's the direction bewteen 2 points , is that a true bearing, a grid bearing or do they mean an azimuth , similar with distance, Spheroidal, Grid or Plane all of which can be derived from either type of coordinate format and relative to the precision of the available coordinates.

 

Of course not all that important with Geocaching unless one wnats to specificy either end of a match (as well as a dozen separate points in between)

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+Waterboy]

Kerry,

 

You said “. equations rather long and something a simple calulator simply doesn't/can't handle and are quite extensive.” You discovered the point. With UTM this is true. NOT TRUE IN LAT/LONG. Let me explain and then write the equations.

 

My original question was to find the distance between two caches. These are actual caches that are less than 2.5 miles apart located southeast of Rochester, NY. There names and coordinates are

Huff & Puff (N 42° 36.392 W 078° 00.160)

1856 Mule Path (N 42° 34.718 W 077° 58.448)

The important thing about these two caches is that one is just east of the W078° longitude line, and the other is just west of the same line. Or they are in different UTM zones, thus difficult to calculate the distance between them using UTM.

 

Now for the calculation:

1. Huff & Puff Latitude = Lat1

2. Huff & Puff Longitude = Lon1

3. 1856 Mule Path Latitude = Lat2

4. 1856 Mule Path Longitude = Lon2

5. Average Latitude (42°35.555’) = LatAve

6. Distance change in Northerly direction (DistN) is equal to Lat1-Lat2. An answer expressed in arc-minutes is equal to the distance in Nautical Miles. In this problem the DistN is 1.674 nmiles.

7. Distance change in Easterly direction (DistE) is equal to (Long1-Long2)*cosine(LatAve). Again we must expressed this in arc-minutes for a distance in Nautical Miles. In this problem the DistE is 1.260 nmiles.

8. Distance=1852*SQRT(DistN*DistN+DistE*DistE) The 1852 is used to convert nmiles to meters.

9. The answer is 3881 meters.

 

Note – Although I am advocating the use of Lat/Long, to do the calculations I defined my own flat plane system, with the midpoint of the line between the two caches as my origin. For units in either northerly or easterly direction I am using nautical miles.

 

Thank you Kerry. The questions you asked helped me to look at the problem in a different way. I hope we meet some day, preferably on a trail leading to a cache.

[Tahosa and Sons]

The most challenging caches out here in CO are done using UTM's. How else could you find them if you didn't go Up The Mountain.

Other than that I use those a lot, either with caching or general hiking in the hills.

They are the easiest way to plot your way when you have a mapping software program. Hell a pencil dot is about 10 meters square and that is close enough.

 

The "Bushwhacker"

Exitus acta probat

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