Monday, August 07, 2006

Land Navigation

Whew! What a weekend. Saturday, I helped a son move, then hosted a birthday party for a grandchild, then went to visit my Mother over at her house. Luckily, all of those things occurred in the same string of towns I call home.

Sunday, I overslept for church (Boo on me) then did a little carpentry, went out to tour the deer lease, then came home to find I was hosting a dinner party. Milady felt like cooking and had invited the kids to help eat it all.

So, life intruded on blogging, which is how it is supposed to be. This is a hobby, after all.

I purchased a GPS reciever this weekend, a Magellan eXplorist 100. It is a basic entry-level receiver and cost about $100.00 at Wal-Mart. I last used GPS units during my stint in the Guard at the turn of the century. They were bulky units and fairly complicated. This little Magellan is small, simple, rugged. The controls are intuitive for folks who operate computers. The old Army units gave position resolution down to 10 meters, which is close enough for infantry operations. This one is advertised to give position resolution down to 3 meters, which is excellent. It is also lightweight, and fits in your shirt pocket.

I sincerely hope the Army has since upgraded their GPS recievers.

I gave the Magellan a good test drive this weekend. GPS devices are small recievers which track signals from positioning satellites and perform math to triangulate position on the ground. I was surprised that I could set it from my kitchen table, tracking three satellites almost immediately after I turned it on. Upon taking it outside, I began tracking eight satellites almost immediately. The more satellites you track, the more accurately you can plot your position.

You can't turn it on when you are running down the road. It has to be still for a moment to locate itself with the signal from the satellites above. Then, it accurately supplies trip infomation, including direction of travel and speed. The speed reporting is surprisingly accurate, within a mile-per-hour or two of the speedometer on my pickup truck. Waypoints are easily set at the touch of a button and it will provide directions if you want to backtrack, or it will provide straight line bearing and distance to any waypoint you earlier set.

At the deer lease, it initially had a little trouble locating itself, but sorted itself out within a few minutes. As we toured the property, I made waypoints by tapping the button and jotted the locations down on a piece of paper. Were I alone, I would have taken time to notate the locations with the editing screen and I easily accomplished that when I got home and matched up coordinates to my notes.

One piece of north Louisiana piney woods looks pretty much like any other, and one section of gravel road is similarly similar. When I got home, I started inputting coordinates into Google Earth and soon saw where I had been. The overview of satellite photography with my recent trip helped make sense of the tour I had t taken and looking at the map helped cement the various locations in my mind. I saved the map to the hard drive of the computer and I can call it up and print it if necessary. It is interesting to note that my deer stand is located at a distance of 21.8 miles from my kitchen table, on a bearing of 006 degrees. It's not very useful information, but it is interesting.

I can see that this device will be eminently useful in land navigation, and much easier to carry and use than the GPS devices I have earlier used. More expensive units combine mapping ability internally with the ability to download information directly into the computer.

This device, like all other devices will never take the place of a good map and compass. Land navigation is a demanding discipline and the responsibility of knowing your location should never be taken lightly. I'm sure that the batteries will go out when you least expect it and the clouds will overcome the horizon. Haze and darkness will render the most advanced of us dependent on the same tools used for centuries to cross unfamiliar terrain. The map, compass and Ranger beads are indespensible.

However, for trekking around a deer lease, this little device is quite useful.

3 comments:

JimBob said...

I have the basic etrek that I got for free. The last time you published 'deer' coordinates I used MS terraserver to look at the aerial photo. Looked pretty built up area. If you got tired of deer you could always go golfing or fishing. I think you can get a cable and software to hook the thing to your computer. A version of GE (NOT the free download) has the capability to input your waypoints from the GPS receiver.
I found it a real pain to edit/rename the waypoints from numbers to 'mnemonic' form.

Rivrdog said...

Batteries are an issue. I am currently using an older Garmin XL12, which uses 4 AA cells, and they only last 6-8 hours in the field.

I started using some 2800 MA/H rechargeables, and now I can run the unit for over 20 hours.

Your new Magellan should go at least 12 hours on two AA cells, so switching to LiON rechargeables should get you at least two daylight-days in the field before changing batteries, which, BTW, fit nicely two to a shell slot in your hunting vest.

The advantage of GPS over map-and-compass is that you can go direct when traversing the woods. With map and compass, you are going to travel landmark to landmark, and the roundabout route is usually half again as long as a direct route.

I have seriously upgraded my mushroom hunting ability since using GPS in the mushrooming woods, both to mark the exact spot of a rhizome, and to navigate between spots, or from the last spot directly back to my car. I go deeper into the woods than I used to also, so there is less competition for the best rhizomes.

If I was hunting commercially (at $40/# there's real money to be made), I would probably quadruple my take with GPS.

mostly cajun said...

That GPS is invaluable when your boat is out of sight of land. It's damned hard to mark a wave top, and I don't do real well with a sextant in the Gulf. GPS has given me the capability to go over the horizon and then point the sharp end of the boat right back at the mouth of the channel I left. Since it's an electronic device, I carry two, an expensive one with the marine charts for the Gulf Coast from Morgan City Louisiana to Brownsville, Texas, and a cheapy for a backup.

I used to pride myself in army land-nav, when I could locate myself within a hundred meters on a paper map by looking at landmarks. The GPS makes that obsolete for the most part.

MC