Mazamas Wilderness Navigation class handouts

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Contours Developing the ability to look at a topo map and visualize the real terrain that it represents is a key longterm skill to develop in navigation. Shaded relief makes this a LOT easier! (The above images were made from Gmap4 free software.) Contour interval = the real world vertical distance represented by each contour line. This is typically 40 feet on a large-scale map. Index contour = typically every fifth line, printed in bold, which has an elevation value printed somewhere on it. This is typically 200 feet on a large-scale map. Widely spaced lines indicate a gentle slope. Closely spaced lines show a steeper slope. Contour lines that touch one another represent a cliff! Concentric circles show a summit. Spurs (ridges) and gullies (valleys) look almost identical. Learning to differentiate between them is an important map reading skill. Here's the main tip: Spurs have contours that bend downhill. Gullies have contours that bend uphill. (Tip: streams always run in gullies, and never on ridges =^) ``````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````` Coordinate systems Coordinate systems, aka grids, let you to specify a “street address” of any point on Earth. 4
Potentially the most important use for coordinates is: “I need help, and this is exactly where I am!” There are three main types in use for land navigation: 1) Latitude/Longitude, 2) Public Lands Survey System, and 3) UTM (the preferred system for us!) An in-depth explanation of all 3 coordinates systems is here: Mazamas.org --> Resources --> Tip of the Week --> Route Planning and Navigation Lat long • Oldest and most commonly used coordinate system. • Used mostly by pilots and sailors, work better over long distances. However, for land navigation, they have drawbacks. (There are 3 different ways to state lat/long coordinates, confusing!!!) • See a complete Lat Long explanation on the Mazamas web Resources Tip of the Week Route Finding and Navigation Public Lands Survey System (PLS) • Created in the 1800s to survey much of the Western US. • Generally used to survey/identify land parcels in rural or wild areas. • This system lays out a series of 1 square mile grids, based on Township and Range. • Mostly seen on US Forest Service and BLM maps, not so useful for backcountry use. • It’s not useful for precise wilderness navigation, but as it’s on some maps you’ll see, you should be familiar with it. • To read a coordinate, give the township, range, and section (and maybe quarter section) UTM (Universal Transverse Mercator) Why do we like UTM? Grids are square and same size - Based on meters, easy base 10 system - One way to write coordinates, not three - Uses only positive coordinates - More accurate (to 1 meter) - Easy to determine coordinates from a map - Easy to transmit coordinates by voice or text - Easy to shorten / round off - Easier to plot compass bearings on map • The UTM system is metric. UTM coordinates are just like the X-Y graphs from high school geometry. The Easting is the X axis, the Northing is the Y axis. • UTM coordinates of a given point can be calculated from a map, or read off of a GPS. • Easting values increase as you move east, and are always 6 digits. • Northing values increase as you move north, and are always 7 digits (in USA). • UTM coordinates are always given in a specific order: Zone, Easting, and Northing. (Remember: Z-E-N) • A UTM grid is typically printed as a 1 km grid across the map. • The UTM grid can be used to quickly estimate distances in km. ``````````````````````````````````````````````````````````````````````````````````````````````````````````````````````````` The four main navigational tools are map, compass, altimeter, and GPS. Altimeters • Altimeters work by measuring changes in barometric pressure. • It is important to calibrate your altimeter regularly in the field to ensure accurate measurements! Encourage everyone on your team to do the same. Do this at points of known elevation. • Altimeters can be used to fix your point position. If you are on a linear feature, such as a trail, stream, or ridgeline, and you can get an altimeter reading, you can plot your point position where the appropriate contour line crosses your linear feature. 5
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Page 3: Map Datums • A map datum is a mod
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Page 9 and 10: Download ANY 7.5 minute map for FRE
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Mazamas Wilderness Navigation class handouts

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