Land Navigation - Ecological 4-Wheeli g Adventures

EDITOR’S NOTE: The brain will absorb what the rear will endure, and Charles’ has endured many Coyote miles. With bachelor’s degrees in biology, chemistry and psychology, and being a registered nurse and licensed vocational nurse, he got lots of practice in class I suspect. He is a senior network engineer with Microsoft Certified System Engineer and Certified Network Engineer credentials, and has another labor of love with the United States Army Reserve. As a sergeant major with the Nurse Battalion, 5th Brigade (Health Services), 104th Division (Institutional Training), and assisted by a staff of 104, he has responsibility for medical training for the Army and National Guard west of the Mississippi. Computers, ham radio (KF6TXI) and 4-wheeling (land navigation) top his hobby list.

(For the complete Ecological 4Wheeling Adventures newsletter navigation reference reprint order 'NAVIGATION - GPS' - compasses, estimating distance, altimeters, topos, benchmarks, speedo/odo, stars - $6 including postage. See address, e-mail, and phone numbers at the bottom of the page.)

The purpose of this article is to provide an introduction to the use of topographic maps and the Global Positioning (satellite) System (GPS).

Where am I? How do I get to…? Common questions when out-of-doors. If you are in the city, you may look at a street sign or the address and then look it up on a map. From the map you will find your current position and can determine the route to your destination.

In the city you use a road map. Moving from where you are to the intersection of First and Main is typically no problem. Finding your way in the field is a little different, but no more difficult.

The key to finding your way in the field is the topographic map. A topographic map contains streets and highways, but it also contains streams, valleys, hilltops, and lakes. Finding your location using the intersection of a stream and a railroad crossing is no more difficult than finding the intersection of First and Main. The reason most people find a topographic map difficult is because of the total amount of information it contains.

GPS, THE TOOL
With the advance of technology, we have the answer to the most difficult question in the field: "Where am I?" Using a GPS receiver, a person can pinpoint their current position. Once you know where you are, it is much less difficult to determine where you have been or where you want to go.

The GPS is not a replacement for a map or even a compass. It is a tool that makes land navigation easier. The GPS can only tell direction if it is moving. To tell direction when stopped you need a compass. Just because the GPS says you are "here," without a map, you do not know where "here" is. Because the GPS is a radio signal, buildings, mountains or a dense forest canopy can block the signal. If there is no signal then the map and compass become even more important. The GPS can tell elevation but the accuracy for elevation is in the ±500 foot range. So if you need accurate altitude, nothing beats an altimeter.

But the GPS has some major advantages. It can tell you where you are. It can show you where you have been. And, if you know where you want to go, it can guide you there. The GPS is not affected by weather and it leaves a trail of "bread crumbs" showing the path you took to your present position. This path can be backtracked to your starting point.

Going to a location programmed into the GPS is a little more difficult than following the "bread crumb" path. The GPS provides a direct line to the destination; it does not take into account any intervening features. But it will continually point to the destination.

For example: Your destination is the ranger station. Between you and the ranger station is a lake. While you are taking the path around the lake, and the gift shop and the river that leaves the lake, the GPS always points to the destination and provides the distance to the station. The GPS will get you to the ranger station, but only a map would have kept you dry by showing you the bridge over the river leaving the lake.

The most common GPS receivers are made by Garmin or Magellan. All models available are excellent quality. Compare individual features and price before purchase. See past Ecological 4Wheeling Adventures newsletters, GPS Part I, October '96 and GPS Part II, November '96, for more on GPS features, how GPS works and buying a receiver.

GPS, TIME AND ACCURACY
GPS time can be extremely accurate. It's on the order of a few milliseconds and is referenced to an atomic clock in Denver. Time accuracy controls position accuracy. The Department of Defense controls the civilian time error called selective availability. Civilian time accuracy is randomly adjusted to produce position accuracy from 15 to 100 meters. U.S. military position accuracy is within 1 meter.

With the advent of the computer and GPS, it wasn't long before mapping software emerged. There are many applications available to interface the GPS and a laptop computer to map your route in a city. Some applications provide a voice interface that will tell you, "Turn right" or "You have missed your turn." These "road based" mapping programs are very good and quite accurate. They can show you exactly where you are and can plot a route to your destination.

Mapping software for the computer and the GPS using topographic data is much more difficult and still fairly new. All topographic mapping programs have minor problems but the manufacturers are working on them. See past articles: Mapping Programs (March '95), Electronic Mapping Revisited (November '96) and Electronic Mapping II (January '97).

There are two commercially available programs for topographic mapping; the first is "Topo USA" from DeLorme. This program takes the gazetteers and places them on the computer. This application contains the entire United States on four CD-ROMs. The scale of the maps is very large. This makes detail inadequate for backcountry driving or hiking. But they are excellent for an overview of any area in the U.S. The other disadvantage to this program is the substantial amount of computer processing power necessary to run it.

[Delorme released Topo USA 2.0 just after this article was written. Topo USA 2.0 contains much more detail than the original version and is now on 6 disks (would have taken 9 disks with the compression technology used on the original version). The detail is greater than the DeLorme gazetteers but not as good as the Wildflower series discussed below. Topo USA 2.0 will soon be released in single region CD-ROMs. Click on the Topo USA 2.0 link for more detailed in formation on this new version.]

The second widely available program is "TOPO!" from Wildflower productions. Wildflower has taken the 1:500,000, 1:250,000, 1:62,360, and 1:24,000 topographic maps from the United States Geological Survey (USGS) and digitally placed them on a CD-ROM. The advantage is that these are the same maps that can be purchased from the USGS and they contain all the data necessary for hiking or vehicle trips. One of the disadvantages of TOPO! is that it consists of a CD-ROM for individual regions, for example, Los Angeles or Sequoia National Park. The user must purchase the data set for the areas of interest. The only note of caution for TOPO! is to always save the document before printing. [Wildflower also recently introduced TOPO!GPS USA to facilitate use of GPS receivers with the TOPO! Line.]

There is one other topographical program of mention: Fugawi from Pinpoint Systems. This is a good program that also uses data from the USGS. The problem is that it can only be purchased directly from the manufacturer and that the mapping data is purchased separately. In this case the mapping data is sold by degrees of latitude and longitude. 1° x 1° (standard) data map CDs are $60 each. As a reference, if you are interested in the Big Bear, San Bernardino National Forest area, it is 3° latitude x 3° longitude. This requires nine (3 degrees horizontally and 3 degrees vertically) CD-ROMs to cover the area at $60 each. The chief drawbacks of this program are its price and difficulty of acquisition.

MAP-RELATED TERMS

Map: A map is a two-dimensional, graphic representation of the earth’s surface drawn to scale. A map uses colors, symbols, labels and line weights (printed width of line) to represent ground features. Maps come in many shapes and sizes and have traditionally been printed on paper. Most people are familiar with a highway map or a street map. This map shows the relationship of city streets or highways to each other, but does not show elevation or other geologic information.

Topographic map: Topographic maps (commonly called topos) show geographic features (mountains, rivers, valleys or vegetation) and man-made features (buildings, roads, power lines, mines). Elevation is represented by contour lines, and symbols and colors represent man-made or geographic features. Some foreign topos (Mexican) also show archaeological areas.

Scale: The scale of a map is the amount of distance represented by a measurement on the map and how it relates to distance on the ground. For example, using a 1:50,000 map; one-inch represent 50,000 inches (a little over ľ of a mile) in the real world. The Thomas Bros.® map many people use for the city is a 1:57,600-scale map. Common map scales are 1:24,000, 1:25,000, 1:50,000, 1:63,360, 1:100,000, 1:250,000, 1:500,000, 1:1,000,000. The 1:24,000 and 1:63,360 scale maps are common United States Geological Survey map scales. As the scale of a map increases, the amount of detail shown is less.

Contour lines: These are the brown lines that represent a fixed elevation. Precisely walking a contour line would mean that you never change elevation.

Colors: Maps use colors to represent different features. Topographic maps use black to represent man-made features, blue for water, brown to show elevation (contour lines), green for vegetation, red for major roads, built-up areas or special features, and purple for undocumented photographic updates.

Global Positioning System (GPS): A system of 24 satellites that provide information to a GPS receiver. Using three satellites a GPS receiver can interpret the two-dimensional (elevation cannot be calculated) location on the earth. With four or more satellites, a GPS receiver can calculate the location and the elevation.

Ecological 4-Wheeling Adventures
P.O. Box 12137
Costa Mesa, CA 92627
voice: (949) 645-7733
fax: (949) 645-7738
email: info@eco4wd.com

[Topographic map terrain features are depicted with contour lines like those shown below]
Hill	Ridge	Cliff