Difference between revisions of "How to use a map and compass"
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Revision as of 06:13, 11 February 2006
Long before GPS, people were using maps and compasses to find their way around. You may be surprised at what you can do with these two important tools.
When we talk about a map in this article, we are generally referring to a good topographical map such as what can be found at Topozone.com or Mytopo.com. Road and street maps are pretty much worthless out in the woods. Topo maps have all sorts of information on them like elevation, water, land types, land marks, etc. These maps usually have enough features marked on them to guide a map reader to the vicinty of the cache. At scales of 1:10000 or 1:5000 an experienced navigator can get to within a few meters of a cache placement. (They also have degree or utm grids or hashmarks on them so you can actually compare where you are on the map to your gps coordinates, or find your gps coordinates if you know where you are on the map).
If you are using a standard base plate compass: Your compass will have a needle built into it that points to Magnetic North (red end), and is inside a liquid filled housing with parallel lines in the housing. The housing can be rotated 360 degrees. There will be a transparent base plate that has a directional arrow.
There are other types of compasses employing various sighting techniques for surveying or map production, but for navigation in conjunction with a map, a simple base plate model is fine.
Taking and following a bearing
][(Image::203.jpg]] To take a meaningful bearing you must know where you are currently located and recognize that location on the map. Of course you also need to know where you want to go and where that is located on the map. When you know these two things simply connect "where you are", with "where you want to go" by placing the compass on the map. Use an edge of the clear base plate with the directional arrow pointing to "where you want to go" to connect those two points. Now while the compass is on the map turn the housing until the lines inside the housing are aligned with *magnetic north. Lift the compass off the map, turn the entire compass (not the housing by itself) until the magnetic needle and N on the edge of the housing are aligned. The direction of "where you want to go" is now in the direction of the travel arrow on the clear baseplate. Sight out to the furthest distinct landmark in that direction and walk toward it. If you can maintain the bearing just keep repeating the sighting process. If the terrain does not allow walking in a relatively straight line then more map reading and less compass reading will be required.
- magnetic north can be determined by looking on the border of the USGS sheet. It will vary with location and may not be totally uniform in an area. It is a good idea to put your own magnetic north lines on the map at home before going out or memorizing the declination at your favorite caching areas.
Determining your location on a map
Yes, it can be done without a GPS