Map Sample

Here's another map sample, this one with a variety of bare rock and boulder features to ponder, including a couple of boulders drawn to scale (the black blobs). Click to see the whole thing:

From Chattahoochee Bend

Boulders, Boulders, Boulders

From Chattahoochee Bend

Boulder count is about 300. Ocad (the map CAD software) has a feature where it will count all instances of a symbol. 300 seems like a lot, but it's not really. The Red Top State Park map, by comparison, has around 1500 boulders. Of course, I am still not halfway done with this map, so the number of boulders will certainly climb. What is unique about Chattahoochee Bend is that the boulders are not evenly distributed (like they are at Red Top). They are in bands, running across the map. And they are much larger than the boulders at Red Top. The largest I have found so far is 16 meters by 20 meters and 5 meters tall. That's big enough to be mapped "real size". Instead of using a black dot or triangle, the boulder is drawn in black to scale on the map - impressive.

From Chattahoochee Bend

From Chattahoochee Bend

From Chattahoochee Bend

From Chattahoochee Bend

From Chattahoochee Bend

It is also very challenging to map so many boulders. I spent five hours on Saturday doing an area only about 300 meters square. Deciding what not to map is very important, as is deciding which symbol to use - small dot, large dot, triangle, irregular triangle, or mapped to scale. Here's a small example:

From Chattahoochee Bend

Between Snowstorms

Big snow yesterday, Saturday 2/13/2010. Probably about 3 inches on the map. So I waited for it to drip off the trees and melt away before heading out there today. Forecast for overnight is even more snow.

From Chattahoochee Bend

I am almost done with another page of the basemap. Worked my way down, down, down and discovered a little pond in the bottom corner of this page.

From Chattahoochee Bend

I cannot figure out the pattern of the boulders. It's either feast of famine. There were dozens on the west side of the spur I am working on, and two on the east side. They are in bands. Once the map is drafted that will probably be obvious, but it's certainly puzzling to the poor mapper while he is out there trying to plan the best use of his time!

And the next spur to the east is covered with more bare rock areas. It looks as if the big shallow reentrant repeats again three or four hundred meters east. But that will all be revealed over the next few trips.

Measurements and Accuracy

Now that I am mapping boulder fields I thought I would describe the process of how I measure the distance between boulders and place them on the field notes. This process works for anything that needs to be measured.

I use a metal ruler, six inches long, with one edge metric and the other in inches. (Take a compass with you when you buy your ruler so you can pick one that is non-magnetic.) The first thing you do is take some blue painters tape and mask off the inch edge of the ruler. Nothing is worse than using the sixteenths by mistake when you want millimeters. Been there, done that, wore out an eraser.

Know your pace count per 100 meters. Not the running pace count that orienteers use, but walking at your mapping stride. Mine is 61 double paces (count only the left foot) per 100 meters.

Make a simple chart with paces in one column, millimeters (at your map scale) in one column, and meters in a third column. I print out my chart and tape it to my map board. Here is the chart I use. You can look at the formulas and see how I calculate everything.

Now how do you use it? Starting from a boulder that you have already placed correctly(!), count your paces to the next boulder. Use your chart to convert that to millimeters. Use your ruler to measure the distance on your map and make your mark (in the right direction, of course).

You can also use the chart to convert from meters to map millimeters. I sometimes carry a laser rangefinder, which can save a lot of steps. Instead of pacing to the next boulder, I use the gadget to tell me the meters, and convert that to map millimeters using the chart.

Why does the chart round off the millimeters to 0.5? Because you really can't make a pencil mark smaller than that, and more accuracy is not always a better thing.

Rock Gardens

Two more good days over the weekend. The weather was cold, but manageable. Finished the bare rock reentrant and crossed the far ridge line. Here the terrain is more eroded. The bare rock seems to have broken apart and left behind large areas of boulder fields. Some of the boulders are house sized. Not McMansion size, but as big as the house I grew up in.

From Chattahoochee Bend

From Chattahoochee Bend

From Chattahoochee Bend

From Chattahoochee Bend

From Chattahoochee Bend

Should be a lot of fun running around in those boulders looking for the right one. There are also more bare rock areas over here where the slope is steeper - something I didn't expect.

From Chattahoochee Bend

I also found an old homesite with a collapsed chimney and a well. The well is one of the really dangerous kind - at some point GAOC needs to get some volunteers out there to fence it off. Here's a couple of pictures:

From Chattahoochee Bend

From Chattahoochee Bend

Rocky Ground

My desire to take photos is inversely proportional to the temperature. The older it is, the less likely I am to fish out the camera, take off my gloves, and record a photo. But the temperature moderated, to a balmy 37 degress, and the sun actually came out for a short time, so I managed to get some photos of he bare rock area that I am currently mapping.

First, the new construction has begun. As always, they make a mess in the process of making something nice. This is the new park road for access to the visitor center. The old road (flat rock road) was dirt and ran right across a portion of bare rock. The new road will swing around to the east and avoid the flat rock.

From Chattahoochee Bend

The flat rock area is becoming clearer now. It is a shallow reentrant, about 300 to 400 meters wide and 800 to 1000 meters long, gently sloping down to the northeast. A reentrant that big is only noticeable on the map - standing there, you cannot tell. It looks like the terrain is either level or sloping away to the northeast. Imagine that it is doted with ponds and lakes, some as small as your living room, others as large as a football field. Now, mentally convert those ponds to bare rock and you have an idea of what it's like. The vegetation is stunted - I can only guess because the rock is just beneath the surface.

From Chattahoochee Bend

From Chattahoochee Bend

From Chattahoochee Bend

From Chattahoochee Bend

From Chattahoochee Bend

East of the bare rock reentrant, the terrain gets much steeper. Well, steep for Chattahoochee Bend, anyway. The rock has eroded and left huge boulders. More about that in future reports.