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It seems there are a lot of folks who do not know how to use half the features provided by their GPS or map. Beyond marking points and then using the �go to� function, there are several things people should know when attempting to navigate.
First of all, switch your GPS units to UTMs. In my Garmin, it�s called UTM UPS. Without getting overly technical, UTMs are a simple X-Y grid system placed over the earth. Because the unit is in meters, it becomes much more logical to use than decimal degrees, or degrees, minutes, seconds. The only way to calculate your position on a map with decimal degrees or degrees, minutes, seconds are with special rulers that few hunters own, nor know how to use, unless they were in the military. For the Average Joe, with a high school-level math skills, UTMs make more sense. Here in Colorado, our coordinates are projected in either Zone 12 or 13 which is a way of refining the accuracy of mapping a 2-D system onto the 3-D earth, usually in map datum NAD 27 (it will say on the corner of your map). But don�t worry about that for right now, unless you�re manually inputting coordinates into your GPS. The first set of digits are called Eastings. Here, they are six digits long, but in reality they are 7 digits, because they start with a zero. This number represents how far east or west you are from the central meridian. The 7 digit Northing is how far you are from the equator, all in meters.
But who cares about that? You should, here�s why. Let�s say you�ve been wandering around hunting and don�t know where you are. You marked your truck on the GPS this morning, so you could get back by simply following a straight line, regardless of what it leads you through. Wouldn�t it be better to know exactly where you are and what you�ll be walking through or whether there is an easier way around to your vehicle? What if you wanted to investigate a terrain feature, whose coordinates you hadn�t previously entered into your GPS? How would you go about doing that?
The vast majority of maps these days have UTM grid coordinates marked on them. They are typically in 1000 meter grid squares or hash marks. For instance, on the National Geographic Trails Illustrated map I am looking at, the numbers on the top, called eastings begin with a superscript 3, followed by two normal sized numbers, on the side of the map, the superscript has two numbers all beginning with 43, followed by two normal sized numbers. So, let�s say our GPS says we are at 0302465E 4317521N. Where is that on the map? Remember these are 1000 meter grid squares. So on the top, the eastings, follow the superscript 3 until you hit 302. What about the rest of the numbers, the 465? That means you are 465 meters east of the 0302 gridline. Basically, within 35 meters of dead square in the middle between grid lines 0302 and 0303. Now, for the northings, 4317521. On the side of our map, we should see a grid line for 4317, then we continue 521 meters north of that line, which once again, puts almost in the middle between the lines for 4317 and 4318. Where those two lines intersect is your position. Understand?
Using that same system, you can also manually enter coordinates into your GPS to navigate your way to a terrain feature.
Many guys these days also don�t know how to properly use a good compass. A good compass has a rotating dial, not a simple north arrow.
Two quick and dirty uses for your compass: staying on a course, or determining a on bearing. How do you do that, and why, especially if you have a GPS?
Let�s say our GPS indicated which direction to head and it was through the timber to our meadow. I don�t know about you guys, but I�ve always had difficulty maintaining satellite reception in heavy timber. Your GPS pointer will tell you which direction the waypoint is, but it might not have a good fix on your location, giving you inconsistent directions. So you stop, letting the satellites find you again and the GPS tells you the direction you need to head to find your meadow, but you know you�ll lose reception as soon as you move. Many GPSes will also give you the direction in degrees. 0 is north, 90 is east, 180 is south, 270 is west. Your direction dial says 45 degrees, northeast. How do you stay on that course? Whip out the ole compass, did you ever notice there is one white arrow, one red arrow? And a red outlined arrow on the dial opposite of the white arrow? We want to go 45 degrees, so rotate the dial to 45, or northeast. Then turn your body or compass so that the red arrow overlays the red outline, that is the rough direction you need to head.
Same idea if you are trying to figure out what direction you are heading. Keep facing that direction, with your compass out in front of you. Rotate the dial so that the red arrow and the red outline overlay each other, then read the indication.
GPS isn�t working? One other use for your compass is to take a bearing. For the moment we will not worry about declination, or how true north and magnetic north differ slightly. Want to triangulate your position on a mountaintop. Take a precise bearing of the prominent peaks listed on your map, then use the compass to help you draw a line back towards your potential position. Do the same thing with two or three other peaks to create an error polygon. You should be somewhere with that polygon. That is the basics of triangulation, and similar to how satellites calculate your position.
I hope this helps somewhat. And hopefully I didn�t leave out anything crucial.


"For some unfortunates, poisoned by city sidewalks ... the horn of the hunter never winds at all" Robert Ruark, The Horn of the Hunter

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great post but I would add that your GPS unit will give you a grid north reading and if you have a compass you need to know your declination for the area you are in. You need to set your declination or correct for it. In some areas it does not make that much of a difference between true-grid-magnetic, however the farther east or west of the central meridian of your zone if you are using state plane coordinates, or the farther north or south you are from the equator you are going to get a fairly large declination. (for instance where I am at in western washington it is 22 degrees. and a guy can get pretty turned around heading on a bearing that is off by 22 degrees) also you need to be aware of what side of the prime meridian you are at. if you are on the east side you declination correction will be northwest whereas if you are on the west side you correction will be northeast. Just something to keep in mind if you use a handheld compass in juncuntion with a gps.


If you get a compass get a good quality one like a silva that you can set your declination on

Last edited by heavywalker; 09/17/09. Reason: compass recomendation







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Originally Posted by exbiologist
The only way to calculate your position on a map with decimal degrees or degrees, minutes, seconds are with special rulers that few hunters own, nor know how to use, unless they were in the military.


Not really. One easy way to get around this is to buy the National Geographic TOPO software for your state (about $100 per state last time I checked) and print your own customized maps. Saves a lot of money if you use a lot of different maps.

You can print your own customized maps with grid lines right on the map, either UTM or degrees, minutes, and decimals of minutes. I use degrees/minutes/decimals because that's what I've always used and my brain is calibrated that way. I can pick any spot on these maps and quickly give you accurate coordinates without a ruler, it's very easy.

The other advantage of printing your own maps is that you can center them where you want and cover just the area you're interested in with an 8 1/2 by 11 sheet, and you can turn over the paper and print another map on the other side--no more carrying multiple maps because the area you're interested in is on the edge. You can print on waterproof stock too, another advantage over conventional maps.




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+1

I take my Nat Geo and print out exactly what portions of a map I need in UTM with the grids. I can take my not so special compass and figure exactly where I am to within 100 yards.

For a lesson in navigation, a person should take a trip to Kifaru and read some essays by a guy named Dick Blust.

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Great post OP. Another thing to do is make sure that the Datum in your GPS is the same Datum as the map you are using. If you dont do this, your GPS is worthless.

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heavywalker; I thought the declination here was 22 degrees also, until a couple years ago when I accidentally looked it up.
I just now googled it again to double check and this is what Chehalis is: 16* 51'E, changing by 0* 9'W /year.
I'm in Longview and here it is: 16* 43'E, changing by 0* 9'W /year.
Google is my hero! smile


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Originally Posted by c86man3
Great post OP. Another thing to do is make sure that the Datum in your GPS is the same Datum as the map you are using. If you dont do this, your GPS is worthless.


I agree that it is a good idea to be aware of the datums being used. However, for practical purposes in simple/typical land navigation, the common datums used in more recent times: NAD 1927, NAD 1972, and WGS 1984 are all going to get you very close - at least not lost. Of course, if what you are seeking is an old obscure trail - which is actually accurately marked on a detailed map- then the correct datum may make a difference.


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Yeah the 22 degrees is refering to the old BLM maps that were made when the GLO originally surveyed the land in washington. The last solar observation that I took at work I was running 16-58-27 and that was in PE ELL about a 4 months ago.








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Originally Posted by Klikitarik
Originally Posted by c86man3
Great post OP. Another thing to do is make sure that the Datum in your GPS is the same Datum as the map you are using. If you dont do this, your GPS is worthless.


I agree that it is a good idea to be aware of the datums being used. However, for practical purposes in simple/typical land navigation, the common datums used in more recent times: NAD 1927, NAD 1972, and WGS 1984 are all going to get you very close - at least not lost. Of course, if what you are seeking is an old obscure trail - which is actually accurately marked on a detailed map- then the correct datum may make a difference.


You are correct that most of the time you can probably get away with not worrying about datums. However, in some places the differences between datums are more severe, sometimes close to a kilometer. There are many applications where being aware of what datum you are using are important! What if someone in your party gets hurt and you need to give coordinates to a rescue team, if you are using different datums you could end up on different sides of a mountain.

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Just to add to what Smokepole said -
Another great feature of the Nat Geo SW is that you can pick out the landmarks or points of interest on your PC screen, download them to your handheld, and you are good to go. This can save a tremendous amount of time in an area you are unfamiliar with. I've found this to always be pretty much dead on even just using the default WGS 84.

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Originally Posted by c86man3
Originally Posted by Klikitarik
Originally Posted by c86man3
Great post OP. Another thing to do is make sure that the Datum in your GPS is the same Datum as the map you are using. If you dont do this, your GPS is worthless.


I agree that it is a good idea to be aware of the datums being used. However, for practical purposes in simple/typical land navigation, the common datums used in more recent times: NAD 1927, NAD 1972, and WGS 1984 are all going to get you very close - at least not lost. Of course, if what you are seeking is an old obscure trail - which is actually accurately marked on a detailed map- then the correct datum may make a difference.


You are correct that most of the time you can probably get away with not worrying about datums. However, in some places the differences between datums are more severe, sometimes close to a kilometer.


I was hoping that someone might correct me if I was interpolating my own local experiences too broadly. (100 yards or a bit more is about it around here, not too much even for SAR.) That's good to know. I appreciate the added info and correction.


Sometimes, the air you 'let in'matters less than the air you 'let out'.

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