View source for Appendix H: Map and Compass Skills

=== Universal Transverse Mercator (UTM) ===
==== Basis of system ====
Distance is measured in meters north and south from the equator and east from a central meridian. 

From the wikipedia entry for UTM: The point of origin of each UTM zone is the intersection of the equator and the zone's central meridian, but to avoid dealing with negative numbers the central meridian of each zone is set at 500,000 meters East. http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_coordinate_system

==== Map marks ====
UTM grid coordinates are the series of black numbers on the white border of the map next to the blue grid ticks. For
example, in the upper left margin of the 7.5-minute Norden Quadrangle appears the number 4361000N. The blue grid tick
to the right of this number marks a distance 4,361 kilometers (4,361,000 meters) north of the equator. In the left end of
the top margin of the map, just below the words "GEOLOGICAL SURVEY" is the number 727000E. The blue grid tick
to the left of this number marks a distance 727 kilometers (727,000 meters) east of the principal meridian. Other similar
numbers on the map eliminate the 000m and express the distance only in kilometers.
==== Using the map marks to describe a location ====
Forget all of the superscript numbers. Henceforth, 4361000N will be referred to as 61, and 728 as 28. To learn how to
describe your location, let's use an example from the Norden 7.5 minute map:
*       locate the summit of Donner Peak in the middle of your Norden 7.5 minute map.
*       draw an imaginary north-south line from your position to the top or bottom margin of the map, and note the blue UTM grid tick numbers on either side of the point where your imaginary line intersects the map margin.  The numbers should be 31 and 32. [Note that while the blue grid ticks are always present, often the numbers are missing and you have to extrapolate them from nearby grid tick references. For example, at the bottom of the map, the reference to 32 is missing, and at the top, the reference to 31 is missing.]
*       Do the same exercise using an east-west imaginary line to the left or right margin of the map, noting the blue grid ticks above and below the point where your imaginary line intersects the map margin. You should fall between grid ticks 54 and 55.
*       Now draw a line between grid tick 31 on the top and grid tick 31 on the bottom of the map. If you don't have a straight edge long enough (and you won't in the field), fold over one edge of the map and use it as a straight edge to connect the two "31" grid ticks. Be certain that the edge of the map is flat or your line will be off.  Next, do the same exercise to connect grid ticks 32, 53 and 54. [We strongly suggest that for training purposes you draw the entire UTM grid on your Norden 7.5 minute map.]
*       Note that the lines you have drawn have created a square box around the Donner Peak reference point. [In the future, you only have to create this "box," and it is unnecessary to draw complete lines between the grid ticks.] Notice that the lines you have drawn are not parallel to the edges of the map, but are slightly skewed. This is because the UTM grid system is not based upon True North, but your map is. From now on, you will focus on the "box" you have just created.
*        within the box draw a line, parallel to the left and right sides of the box, from the summit of Donner Peak to the nearer of the top or bottom margin of the box. [In this case, the bottom margin.]
*        divide the distance along the bottom margin into ten equal parts, and record where your line intersects the box margin to the nearest tenth. You should find that your line intersected the bottom margin of the box 8 tenths of the distance from grid line 31 (the left side of the box) to grid line 32 (the right side of the box), and thus you should record 318. [It is actually 31.8, but the decimal point is eliminated.] [Try using your UTM grid reader to speed this process.]
*        next, draw a line, parallel to the top and bottom margins of the box, from the summit of Donner Peak to the nearer of the left or right margins of the box. [In this case, the right margin.]
*        again, record where the line falls to the nearest tenth. You should find that the line intersects the right box margin 3 tenths of the distance from grid line 54 to grid line 55, and thus you should record 543.
*        then simply combine the two three digit numbers into one six-digit number, giving the east-west coordinate before the north-south coordinate. In our example 318 and 543 would produce "UTM 318543 on the 7.5 minute Norden Quadrangle." (Note that we reference the particular map because you might get a slightly different reading using a 15-minute map of the same area.)

PRATICE PROBLEM 1: Try determining the UTM location of the triangle marking the tablet atop Anderson Peak,
located roughly 1 3/4 inches from the bottom margin and 6 1/2 inches from the right margin. See answer 1 on last page
of this appendix.