Map geeks only - Public Lands Survey (PLS) system explained

Most maps of National Forests in the Pacific NW have a checkerboard-type coordinate grid.  Here’s an example near the North Sister area in central Oregon, scanned from the Willamette National Forest map:

What is this checkerboard, and how might it be useful for you in backcountry navigation?

The answer:  It’s called the Public Lands Survey System, or PLSS.  It’s the system started in the 1800’s to survey much of the rural land in the US.

Here’s a short explanation, based on the graphic below:

1. First, a principal meridian and baseline are surveyed (the red lines).
2. Along these, townships and ranges are surveyed.  These are square blocks 6 miles square on a side (the yellow squares).
3. Each 6 square mile township/range block is divided into 36 smaller squares, each 1 mile square.  These squares are called sections (the green squares).
4. Finally, each 1 mile square section can be subdivided into quarter sections, each 1/4 mile on a side.

image from: http://geology.isu.edu/geostac/Field_Exercise/topomaps/plss.htm

How might this be useful to you in the backcountry?
While not as precise as using UTM coordinates, you can still specify your position pretty well with PLSS coordinates.
If you can determine your township, range, section and quarter section, you cna specify your position down to a 1/4 mile square.

For example, the Renfrew glacier on the NW side of Middle Sister would have PLSS coordinates of: Township 16S, Range 8 East, Section 29, SE quarter.

And to wrap it up, here is a good, short (3:23 minute) YouTube video that explains it quite well:

Map and Compass Basics: Township and Range
http://www.youtube.com/watch?v=opoWsz7Mbc8