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Using Utm With Our Gps?


95_Camaro_Couple
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Hi All! Alright, so my soldier husband says he wants to use UTM when geocaching. No problem, since the cache description pages also list the coordinates in UTM. Now though, for the life of me, I can't figure out how to get my Legend to go from Lat/Long to UTM. I've looked through the owner's manual enough times that my head is spinning and frankly, I'm so frustrated that I'm not seeing *anything.*

 

Is there anyone who can please explain the process to me, step-by-step, like I'm an idiot? I really appreciate it!

 

I'm also wondering if my ignorance of the science and math of geocaching, and using GPSs in general, is taking away from the true experience of the sport? I mean, I'm all about hunting and finding...at first, I thought that's what the sport was all about and I've had fun just from that experience. But now I realize how much more in-depth it goes, and I can't wrap my brain around it. I constantly feel inadequate.

 

Heck, if you have a question about changing out a 4L60E transmission then I'm your girl...but please don't ask me to explain anything other than the basic details of geocaching!

 

Thanks,

 

Paula :huh:

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Go to the main menu screen, you will find a icon with the text "Setup", the "setup menu" screen will be displayed, then highlight the "Units Icon", you will see a form titled "Units", select the "Position Format" input and hit enter key, a list will be displayed where you can choose the UTM coordinates.

 

Well, harleycache helped you before

Edited by garri
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5) Scroll down until you find UTM (There is a UTM UPS and a User UTM Grid. I don't know which is which so you're on your own there)

Use the UTM UPS!! And that means in broken italian U Pretty Sure.

And if you combine the UTM's with National Geographic Topo you can make a map with UTM grids at 500 meters and then just plot your positon using a roamer scale

or a 3 x 5 card and make a roamer from the map scale.

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UTM has its problems, such as not matching physical reality, such as not pointing north accurately, such as having problems projecting across zone boundarys, but, yes, in close quarters it gives you great distance to position relationships.

 

On switching, in many Garmin units if you have the unit set to UTM or any other format, you can switch back and forth to the default HDDMM.mmm easily while on the satellite/position page by pushing the rocker up and down.

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I agree with UTM.

 

I saw everything in Lat/Lon and thought - crap: civvy talk. I HATE lat/lon - after learning UTM, I could never go back .. but I have had to.

 

When I hide multi caches, I will use UTM only *snickers*

 

Heck, even bought my compass because it is calibrated in mils, not degrees!!

 

MILSPEC for life!

 

PS: 1 degree = 17.7 mils

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"PS: 1 degree = 17.7 mils"

There you go again. Reverting back to lat/long. Admittedly, I have rarely used UTM, but I can see its usefulness, but what do you guys do when you bump up against a zone boundary and the cache is on the other side? How about when you are looking for north and away from the central meridian. Isn't it a problem that north has swung east or west and ain't north?

 

UTMzone.gif

 

One thing I do agree with and that is the metric aspect of UTM. It's crazy that we in the USA haven't went metric yet.

Edited by EraSeek
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The fact is that north is a relative thing - and you account for it by declination (including variation between grid north and "true north").

 

I absolutely LOVE seeing a map in UTM - and the only better thing than calling out an 8 digit grid reference is finding the bearing to your waypoint using mils.

 

As a point of interest, 1 mil = the angle formed when an object is moved 1 m perpindicular to a central point at a distance of 1 km (1000 m).

 

When you combine mils and UTM, it is all metric which = VERY NICE!!

 

To back up my first statement that north is a relative thing, check here:

 

Daily travel of north pole:

 

http://www.geolab.nrcan.gc.ca/geomag/daily_mvt_nmp_e.shtml

 

Long term movement of north pole:

 

http://www.geolab.nrcan.gc.ca/geomag/long_mvt_nmp_e.shtml

 

[Edit: Included references]

Edited by =BB=
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Yes, I've posted those links before as to Magnetic North. First of all, I don't use Magnetic North because it isn't north. Secondly 85km is nothing at that distance, and would be unnoticable to a compass user in the US. However, north in a UTM zone can vary significantly when moving away from the central meridian. So no, it isn't relative. There is True North, magnetic north and user north.

 

Not only does magnetic vary each day and over time, local anomolies exist as well, and of course one needs to deal with declination to find true north when using a compass. Nice thing about GPS's is they already know True from the sat fix and must be set to magnetic to find the declination to make to an adjustment to magnetic.

 

That is interesting about mils. Never knew much about it.

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Actually .. talk to anybody who deals in precision and accuracy and they will tell you that: yes, north is a relative notion.

 

Talk to any physicist and they will tell you that north is a convention and should be replaced by the axis of rotation. And then follow up to say that due to the motion of the "magnetic north pole" the notion of north is in fact relative.

 

Whether or not the end-user cares is their problem <_<

 

To jab at your GPS comment, GPS units are pre-programmed with the decination data and this can not be corrected for by satelites. This is a well noted problem with the GPS system. A GPS unit uses the date and coordinates and then cross-references pre-calculated declination data for the local region - far from acurate when you deal in long-distance telemetry (ie. microwave aiming).

 

On a barely related note, as an object moves through a magnetic field (:lol: [such as the earth's], an EMF (E) [electro-motive force] is created as a function of velocity (v) and L (distance between points) and the angle (theta) at which the velocity and magnetic field vectors meet.

 

E = vBL * sin(theta)

 

So, how fast would a person with an arm span of 1.8 m have to run across the earth's surface with arms stretched to power a 3.0V walkman if the earth's magnetic field has a strength of 5^-5 T ?

 

Answer: v = E / (BL sin 90') and thus the velocity required is approximately 33'000 meters per second !!

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"To jab at your GPS comment, GPS units are pre-programmed with the decination data and this can not be corrected for by satelites. This is a well noted problem with the GPS system. A GPS unit uses the date and coordinates and then cross-references pre-calculated declination data for the local region - far from acurate when you deal in long-distance telemetry (ie. microwave aiming)."

 

I'll do some research on this but just as WGS84 is geocentric so the Gobal Positioning System is as well. Whether declination is pre-programed in or downloaded with the data stream corrections from the sats matters little. It only applys when you use Magnetic North. It is my understanding that the GPS makes the adjustment TO magnetic when it is chosen. True North is the default.

 

But I guess I understand what you are saying. I tend to think in terms of WAAS, and in that case being in the data stream corrections would make sense, but for normal GPS it declination would probably have to be preprogramed for use when Magnetic is chosen.

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"To jab at your GPS comment, GPS units are pre-programmed with the decination data and this can not be corrected for by satelites. ........."

Just for info - the last SW upgrade for my Garmin 3+ had this in it, so I would say the declination was sorted out in the GPSr.

 

Changes made from version 2.05 to 2.06:

 

...............

Updated magnetic variation tables based on the IGRF 2000 model.

...............

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Something I came across is UTM from the GPS not matching what was on the map. Took a little while then remembered the spheroid setting in the GPS has to match the map I was using. Geocaching primarily uses WGS84. Some military maps may have something like Clark 1886 or others. Just something to keep in mind.

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If I could easily get maps with UTM grid reference lines I wouldn't even need a GPS to geocache. I too am military and am trained in this system. I can just eyeball a military map for a couple of seconds and see where a coordinate is.

National Geographic Topo maps that use the 24k USGS quad maps can print any map with the 1000 meter grid line and give the UTM coorindate on the line. For zoomed in printouts, you can change the grid to 500, 200 100 or whatever meters you'd like for more easily calculating where you are.

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Ok, I did a little research to back up my claim that north is distorted as you move away from the cenral meridian (this being one of the flaws of UTM). Here is what I found:

 

"Grid North

Since meridians converge, the UTM grid coincides exactly with compass directions only along the central meridian of each zone. For Green Bay, in zone 16, that meridian is 87 degrees west. Elsewhere, the grid makes an angle to the meridians, and at the edges of the zone it's pretty noticeable. It's important to note whether azimuths are being plotted with respect to true north (meridians) or grid north (the north-south lines of the grid). This information, along with the direction of magnetic north, is plotted on most topographic maps. Military people, who work with UTM grids all the time, tend to rely on grid north. Scientists in the field, who are more likely to use the UTM grid only for recording locations, might opt to use whatever is most convenient.

 

Exercise: What is the largest possible difference between grid north and true north (except in the polar zones)? Answer below"

The answer is 3 degrees. Not really all that bad.

 

The biggest flaw are the zone boundaries and the inability to translate coordinates and distances between zones.

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Actually .. talk to anybody who deals in precision and accuracy and they will tell you that:  yes, north is a relative notion.

 

Talk to any physicist and they will tell you that north is a convention and should be replaced by the axis of rotation.  And then follow up to say that due to the motion of the "magnetic north pole" the notion of north is in fact relative.

 

startrails.jpg

 

Stand below this spot and you are at the True North pole. So tell me, how is this a relative notion? And as for what to call it, here is the defination I found:

 

"Deviation, declination and variation

Here are three terms frequently encountered when using compasses to find bearings for navigation. Are you clear what each one means? And what about the three norths, too?

 

True north (Geographic north)

The location of the earth's axis of rotation and is the basis for lines of latitude and longitude. (90°N, where all meridians of longitude intersect.)

Magnetic north

The north direction shown on a compass determined by the earth's internal magnetic field. The true north pole and the magnetic north pole are currently about 1500km apart.

Grid north

The north direction taken from grid lines on a map or chart. These vary from exactly true north-south lines due to curvature of the earth's surface and the effect of representing this curvature as a flat surface.

Deviation

The error in reading a bearing from the compass caused by the magnetic influence of some nearby object, such as a metal post or a car parked beside you. In the case of boats it may even be due to the materials from which the boat is constructed. Electric currents close to the compass will affect its behaviour. To avoid this type of error the compass should be kept away from all such influences. Most boats have some measure of deviation which should be minimised by careful mounting of the compass. Deviation changes each time the boat alters course. There are people skilled in compass adjustment who can issue a card for a particular compass with deviations listed for changes in direction.

Declination (also known as variation)

The error caused by the earth's magnetic field. For a magnetic compass, the needle will point towards magnetic north rather than true north. Depending on where you are on the earth's surface this difference may be as much as 30°. Variation (declination) may be to east or west of true north, again depending on where you are on the earth's surface. In Queensland variation (declination) is about 11° easterly. Variation (declination) also changes as time progresses (as the magnetic north pole changes position). This information is always shown on maps and charts (usually in the compass rose) with a base year and a statement to say 'increasing...... each year'.

Edited by EraSeek
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Do note that the reason geographical (true) north was selected deals very much with the fact that the meridians of longitude converge at the point: axis of rotation.

 

Our earth wobbles. And hence the "true" north is also a relative notion.

 

Think of where longitude came from in the first place.

 

:o

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UTM is accurate to 3.28 feet, whereas Lat/Long is accurate to 6 feet.

I assume what you are saying is if you have your gps set to utm / or set to Lat/Long these are the how close you coordinates read outs will take you

ie Wxxx xx.ooo in lat/ long defines down to 6' to 4' feet depending on your latitude. That is not the same as accuracy of either a coordinate system or your GPS. It is simply the limit of your coordinate read out in your model of GPS. Niether does it express the the superiority of one coordinate system over another.

 

In fact when I have my GPS set to lat/long and have it GOTO a target, my gps will tell me 10' to target. 5' to target, 0' to target... even though the coordinates have stopped defining my position at Wxxx xx.ooo which works out to somewhere between 6' and 4' where I live. However, the inaccuraacies and errors in both my GPS and yours is hardly that reliable (accurate) at defining a position that close.

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UTM is accurate to 3.28 feet, whereas Lat/Long is accurate to 6 feet.

Hadn't thought of that point. Accuracy is not the right term. Your GPSr accuracy is no different whether or not you use UTM. However precision is different. .001 minutes is roughly 6 feet while 1 meter is roughly 3.28 feet so using UTM will, on most units, be more precise.

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Ah! So if the physical world does not match our mathematical notion of absolutes, (it wobbles), then there are no absolutes! And the moto of West Virginia stands correct: "Everything is relative" :o

 

Its been fun ;)

You raised a great point! Perhaps I see things too much from a scientist's perspective. For every day use I use north as an absolute as opposed to relative - but for argument's sake I turn to math and hence relative. B)

 

Just to reiterate to those who are simply skimming past the "real meat" of this conversation, on UTM maps, there is a declination arrow for true north + a declination arrow for the difference between grid north and true north.

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:o OK, as a retired Artillery NCO (13C), with a four year stint in the light infantry (11C), I used the UTM system regularly. For plotting points on a paper map, the UTM system can't be beat (IMO). However for Geocaching, I guess it just doesn't matter to me. I use EasyGPS to load the caches in my GPSr and select the waypoint by using the 'go to nearest' function. I then follow the arrow to the area and 'Voila' there is the cache. I've recently changed my display to 'statue'. Being the cronologically impaired individual that I am, I'm still more comfortable in feet and miles. That's what my car odometer reads in, so I just find it easier to use. So I guess what I'm saying is that if a person has to have a paper map, then UTM is probably the way to go, otherwise since I'm only going a few miles and to a single point (most of the time), it just doesn't matter.
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Maybe I'm getting in a little late to this conversation, but I agree with the guy above me but would add that I use my GPS in conjunction with my map when things look a little tricky. My 1:50000 scale (military) map helps me to figure out whether that cache in on this side or that side of that thing. And because they're free where I work, why not factor in another aid to the GPS.

And for the record, I'm currently a 25A (Signal Officer) and was previously an 11B (light infantry) and use UTM all the time and love it (probably because I understand it).

 

POLARBZ

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