'CORE CLINIC' Maps and Navigation
EQUIPMENT Map, compass, and a clear head are mandatory. Altimeters are now widely accepted and very popular due their decline in price in recent years. A pencil, small protractor or ruler are handy.
COMPASSES Simply stated a compass is a device with a magnetized needle that is free to rotate and point to "magnetic north" - a subterranean mass of ore that is in the general direction of the physical North Pole. Simple clear plastic base plate compasses are useful for trail navigation and map orientation, hand held lensatic compasses are useful for "shooting a bearing" of a landmark but not as easy to integrate with a map. The best and most accurate all around type is a mirrored sighting compass with a clear base which allows both map orientation and also sighting or shooting a bearing to various features. Some nice compass features include a free floating needle, the ability to adjust/fix the declination to your particular map, a rotating bezel with luminescent markings and fine definition, a ruler/map scale, magnifier and a lanyard.
ALTIMETERS Hand held or wrist mounted altimeters are incredibly helpful as well - they provide elevation as calculated from atmospheric pressure. Sea level pressure is relatively stable and therefore is the basis for calibrating our altimeters. As we ascend pressure decreases and our altimeter registers the relative increase in elevation. Atmospheric pressure is also effected by weather and must be considered in our calculations - conversely our altimeter can be used as our personal weather station and for strategic planning while back packing and mountaineering. Analog (dial) altimeters function on an aneroid capsule basis - just like less accurate home wall mounted units. Electronic models are less costly, feature easy to read (and set) digital displays and a multitude of other useful functions. Bottom line - altimeters are extremely useful and give you the power to "fix" your location on the vertical axis - one third of the navigation game. If you are on a trail, following a stream, hiking a ridge or any other known "travel aid" or are hiking at night, in the fog or in a white out, an altimeter can give you an exact location without having to rely on a compass and your ability to sight landmarks.
MAPS Maps are "general guides to terrain, land forms and man made features". What might be helpful to our understanding of map scale is to start with how cartographers divide up our Earth. A measurement east or west is called 'longitude'; a measure from north to south is called 'latitude'. Longitude is measured by 180 degrees, both east and west starting from the Greenwich meridian in England. The latitude is measured by 90 degrees, both north and south from the equator. These degrees are then further divided into 60 units called 'minutes'; and even further divided by 60 'seconds'. An example of these measurements would be our location here in Monterey: 121o 52'30" W longitude and 36o30'N latitude. These degrees of latitude and longitude can be found on the edge of our map in large, light type.
USGS topographic maps - the most common for hiking and back packing - are produced in roughly 7.5 minute "quads" (that's 7' 30" of longitude). Less common and no longer produced are 15 minute quads which covered twice the area (and half the detail) of the current scale and format. On our modern 7.5' U.S.G.S. maps we are shown a map scale in the center of the map at the bottom along with measurements of distance. 1: 24,000 scale tells us that our map is scaled down in size 24,000 times the actual distance shown on the map! A variety of Map Symbols are found on each quad and a complete list is available. There are contoured lines of elevation, streams, rivers and lakes, shaded areas of vegetation, Bench Marks (surveyed and marked geographic points), Township and Range divisions (red lines), roads, tracks and trails, to name a few.
Before we find ourselves on our map, we must first 'orient' our maps to 'true' north, this will give us a better idea of our relationship of the map to the countryside. Simply align your compass with the declination marker in the legend on your map (in the lower left corner) and align the compass needle's north bearing end (usually red) with the 'magnetic-north' arrow on the diagram. Your map is now oriented to 'true-north' and can be used to identify prominent land features. If you are hiking trails many times orienting the map and then using it for reference is all you need for general navigation purposes. The next camp is not far and some trails even have directional and mileage signs - however these can not always be relied upon.
For more precise navigation, sighting a bearing to a known landmark will determine a "line" (the azimuth) that you are on. Additional sightings (minimum of three) will triangulate your position on this primary line with some degree of accuracy. Developing this skill is very useful when you are traveling cross country (off trail), on "unmarked trails" or on snow. Couple this with a reading of elevation from your altimeter and you have a very accurate means of calculating your position. Like all things, practice makes perfect and with these tools creates an awareness of position and direction of travel - useful in the mountains for sure, convenient around town and on the highways as well.
BOOKS & MAPS
We stock 16 U.S.G.S Quads that cover our local Los Padres Forest & The Ventana Wilderness, The Monterey Peninsula plus other popular destinations & areas. Maps can be ordered for any part of California or the U.S. and even some National Parks are depicted in special format and scale.
RESOURCES Monterey Bay Orienteering Club (visit via our web site, click on Local Beta, then Monterey Bay Orienteering Club)
U.S.G.S. - Middlefield road, Menlo Park (a good field trip)