Ginohn's Forest
[how to map]
A map of the woods behind Ginohn's place.
How Ginohn Maps the Trails

Equipment - compass, pencil, and paper
Now and then when walking Booda in the woods, we carry a few extra things: a compass, a small notebook, and a pencil. This is probably the minimum amount of stuff you need to make a pretty accurate map of trails.

The compass that we are using is an orienteering style magnetic compass with a mirror sight. We recommend a mirror sight, because once you learn how to use it you'll find that it is more accurate and faster than compasses without sights. It's more expensive but worth it.

Carry a notebook or a few sheets of paper, and make sure they'll fit in your pocket. Since very little data has to be taken for each path, not much paper is needed.  It's always nice after mapping points along a trail to be able to put away the equipment and enjoy the rest of the walk.

When Ginohn collects map data, John carries the compass and Gina carries the notepad. We can probably easily fit all mapping data for the entire woods into one small notebook (3x4 inches, about 100 pages), so Gina carries this notebook out with her. It'll be nice to have as a memento later, and it's always good to keep a master hard copy. Pages are numbered so we can refer to them when paths meet up or cross. Currently we are just starting page 20.

Path by path, point to point
We map one path at a time, and make sure that each path that we are mapping starts from another already mapped path. Our first mapped path, Linda's Entrance, starts at an arbitrary point on the graph (in this case at 0,0 on the graph above, far left).

From the starting point of a path, Gina will walk ahead until the path makes a turn, crosses another path, or passes a noticeable landmark. There she will stop and write down a few notes regarding her position, such as "med/large oak at center of crossroads."

While she is noting her position, John sights her direction from the last position, where he happens to be standing. After he has a direction locked in, he walks toward Gina, counting his paces. When he gets to Gina he gives her two numbers to write down -- a direction (in degrees) and a distance (in paces).  Once the information is recorded, Gina walks to the next location along the trail. The process of walking and pausing to sight or write doesn't slow down our walk much, and Booda has gotten used to our strange behavior.

Hacking out a map
Once we get back home the numbers and notes are added to our ever-growing spreadsheet on the computer. We could, of course, just draw on some graph paper, using a ruler and compass (the drafting kind) to follow the path coordinates that we noted while in the woods, but we have a computer so we might as well use it for something other than surfing the web, right?  Besides, mistakes are fixed quickly on the computer, and it is a much faster and accurate map drawer than we can be, once it's told how to do it.

Polar to rectangular coordinates (for aspiring nerds)
The trick, when "graphing" a map from the spreadsheet, is knowing how to convert polar coordinates (i.e. direction and distance) to rectangular coordinates (i.e. X and Y, vertical and horizontal distances on a graph). There are trigonometric formulas to perform this conversion:

X = d * cos(t)
Y = d * sin(t)
Where d is distance, and t is degrees (converted to radians). Now instead of having two numbers, t and d, representing the direction to turn and how far to walk to get to the next point, you'll have two numbers, X and Y, representing how far to walk along an North-South vector and then a East-West vector to arrive at the same point in two dimensional space (we're ignoring the hills and valleys in the woods for purposes of the map). When you string together a series of Xs and Ys, each time adding them to the previous points, you'll eventually have a list of points to graph. Here is Booda's Run, in ready-to-graph listed coordinates:
Booda's Run
  Y      X
 40    -31 <<-- Linda's Entrance ends here
 54    -50
 85    -55
102    -55
126    -76
137    -78
150    -81
174    -84 <<-- Eris Hill will start with these coordinates
Notice that the Y column comes before the X column. This is done so that when the computer graphs the paths, North ends up at the top of the screen instead of the right hand side (or something like that -- it's a minor graphing quirk; you'll figure it out when you make you're own map).

Advantages and tests for accuracy
The great thing about mapping this way, on a path-to-path basis with a computer being used as cartographer, is that any time we map or re-map a path, the data is easily added to the graph. Our results can be checked quickly, and our accuracy can be proven in some cases. For example, when Eris Hill (marked in yellow, starting at the end of Booda's Run and going North toward Laurel Entrance) was mapped, the North end of the path could have overshot or run short of Laurel Entrance, which was already mapped. Instead, the two paths met up nicely, very close to the same point along Laurel Entrance where Gina had written, "Double tree @ crossroads."

By fiddling with the spreadsheet's graphing application we can smooth the lines to each point and make wider paths thicker on the map.  Eventually we'll be sticking in symbols for landmarks too.

A note about North
True North, i.e. in the direction of the North Pole of the Earth, is not the same as magnetic North, which varies greatly from one place on the planet to another. Magnetic North can also change slowly from one year to the next. Around here, magnetic North is off by something like 10 degrees from true North. This is no big inconvenience for us, we're happy enough to have a magnetic field that works with our compass.  Most maps you buy in the stores show true North, some even show magnetic North; ours shows only magnetic.

Extras
There are a few other things to take care of, besides finishing the map, which will probably take a long time (it's a big woods). These include determining about how far one of John's paces is, so we can present the map in standard units (like meters); and calculating the uncertainty of measuring with paces. We'll cover those in later installments.
[map] [text] [cetera]