Trasharoo Presents: Map and Compass Class - September 13th-14th

FishPOET

Adventurer
GOALS

To know where you are

To be able to describe your location to others

To know where others are when they describe their location to you

To be able to plot a route to a location

To be able to project a bearing and calculate distance to a landmark

To be able to follow a bearing from point A to point B around obstacles

To be able to visualize an area

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Map Projection
A map projection is a way to represent the curved surface of the Earth on a flat surface. A good globe can provide the most accurate representation of the Earth. However, a globe isn't practical for many of the functions for which we require maps. Map projections allow us to represent some or all of the Earth's surface, at a wide variety of scales, on a flat, easily transportable surface, such as a sheet of paper. Transverse Mercator is the map projection used by the USGS to produce 7.5 minute topographical maps.

Types of Maps
We will be discussing 2 types of maps: Planimetric Maps and Tophographical Maps. Planimetric maps show the positions of features without showing their relationship to hills and valleys. A topographical map (Topo) uses contour lines to show relief.

Map Scale
The scale of the map is determined by the amount of area covered by the map. 1:24,000 is a typical scale for USGS 7.5 minute quad maps. This type of scale is known as a ratio scale.

Minute
A minute is a unit of measurement of angle. In a full circle there are 360 degrees. Each degree is split up into 60 parts, each part being 1/60 of a degree. These parts are called minutes. One minute at the Earth's equator is one nautical mile.

7.5 Minute Quadrangle Map
Originally the USGS produced 15 minute maps but the scale was too small to be practical. The USGS decided to quarter the 15 minute maps creating the maps we use today, the “7.5 minute quadrangle map” or 7.5 minute quad.

Contour Interval
Contour interval is the distance between contour lines. The most important thing to remember is: CLOSE contour lines mean STEEP terrain and OPEN contour lines mean FLAT terrain. Every fifth contour line is an index contour. The index contours are bolder and have the elevation marked every so often.

Features & Symbols
USGS topo maps have more than 60 layers of features and symbols that can be added. Features are shown as points, lines, or areas, depending on their size and extent.

Datum
A geodetic datum is a reference from which measurements are made. The three most common datums used today are:
North American Datum of 1927 (NAD27)
North American Datum of 1983 (NAD83)
World Geodetic Survey of 1984 (WGS84)

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Public Land Survey System
The PLSS is most often used on topographic maps published in the United States and has its roots in the early surveys of North America in the 1700s.* The PLSS is useful in that it is a good way to give a quick approximation of a location, but the main drawback is its lack of accuracy and lack of knowledge by the general public. In each state early surveyors established an “Initial Point”. From the initial point a principal meridian running north-south, and a base line running east-west were established. The initial survey lines served as a basis for subsequent survey lines spaced at 24 mile intervals. Further subdivision of these ‘squares’ led to the creation of 16 smaller squares measuring six miles on a side. When measuring in a north-south direction, each of these squares is called a township. When measuring in an east-west direction, each of these squares is called a range. Each township is further subdivided into 36 smaller squares covering roughly 1 square mile

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Latitude and Longitude
Latitude and longitude is a global system which precisely identifies locations using the equator as a reference point for latitude and the prime meridian as the reference point for longitude. Latitude and longitude is an angular measuring system.

Latitude lines circle the earth parallel with the equator, running in an easterly and westerly direction. The equator is 0° latitude. The North Pole is 90°N The South Pole is 90°S All other points on earth have latitudes in between. When stating position coordinates latitude is always first.

Longitude lines run true north to true south between the poles. Longitude is the distance east or west of the prime meridian. The prime meridian is 0° longitude. All other points have longitudes ranging from 180° east to 180° west. Lines of longitude are not parallel. The closer they are to the poles the shorter the distance between them.

Latitude and longitude coordinates can be described in multiple formats and datums. It is extremely important when giving latitude and longitude coordinates
that you include the format and datum.

Because of the number of steps involved and the geometry involved we will not be discussing how to acquire latitude and longitude coordinates with a map and compass at this presentation.

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Universal Transverse Mercator
The Universal Transverse Mercator projection and grid system was adopted by the U.S. Army in 1947. The UTM system divides the earth into 60 zones each 6 degrees of longitude wide. These zones are numbered 1-60. Each zone is divided into horizontal bands spanning 8 degrees of latitude. These bands are lettered from C to N. A square grid is superimposed on each zone. It's aligned so that vertical grid lines are parallel to the center of the zone, called the central meridian.

UTM grid coordinates are expressed as a distance in meters to the east, referred to as the "easting", and a distance in meters to the north,*referred to as the "northing". When writing UTM coordinates the numbered zone comes first, then the horizontal band letter, then the easting followed by the northing. The northing will always have an extra digit.

The USGS 7.5 minute quad has UTM grid ticks spaced every kilometer or 1000 meters. The vertical grid ticks determine easting position and the horizontal grid ticks determine northing position. If you want more accuracy than 1000 by 1000 meters then you can use a UTM scale or a UTM grid overlay. The scale of the grid overlay must match the scale of the map.

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Understanding the Compass

The compass is a device that has an arrow that aligns itself with the local lines of magnetic flux of the earth.

An angle of direction is marked in a circle around the compass needle. The method of describing direction that we are most familiar with is the “Azimuth System”
Azimuth is a horizontal angular measurement starting at the north meridian and measured clockwise in degrees from 0°-360°

In land navigation, a bearing is the angle between two lines with one of the lines being north.

The many purposes of the compass
A good compass is more than just a direction pointer.
A good compass should have the following capabilities:

It points to the magnetic North Pole
It points to geographic or map north (It can orient a map)
It has scales for measuring length
It has map scales for measuring distances
It can be used as a straight edge
It can be used as a protractor

Some compasses can also be used for:
Determining slope
Measuring the height of objects
UTM grid measurement
A signal mirror

At best a good compass used by an experienced outdoorsman is accurate to +/- 2° More often than not a not so good compass used by an occasional outdoor recreationist is more likely to be off by 5° or more. 1 degree of error is equal to 92 feet of error per mile traveled.

Parts of a Compass
The magnetic needle points parallel to the local lines of magnetic flux

The compass housing can be turned to set a direction of travel or to measure an angle

The compass has an orienting arrow. You “box” the magnetic needle inside this orienting arrow to set your direction of travel. It can also be used to measure angles on a map

There are 2 or 4 orienting lines that are parallel to the orienting arrow. They can also be used to measure angles on a map.

The direction of travel arrow points to your direction of travel.

Three Norths
There are 3 Norths we need to consider when working with maps and compasses

Grid North or Map North:
The direction your map is oriented to. The left and right margins of your map are grid north.

True North:
The direction of a meridian of longitude which converges on the North Pole. When taking an bearing from true north the reading is call true degrees.

Magnetic North:
The direction indicated by a magnetic compass. Magnetic north moves slowly with a variable rate. When taking an bearing from magnetic north the reading is called magnetic degrees.

For land navigation we do not concern ourselves with any difference between grid north and true north as they are less than 1° difference.

For land navigation we must concern ourselves with the difference between map north and magnetic north. This difference is called MAGNETIC DECLINATION.
The magnetic declination locally is approximately 14°

There are 2 ways to compensate for declination

Manually – your compass has the ability to manually adjust for magnetic declination. When the compass has this ability you have the option of using true degree readings or magnetic degree readings.

Arithmetic - users of compasses that do not have manual magnetic declination compensation capability can use arithmetic to compensate.

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Using a Map and Compass together

You can orient your map in one of two ways: Track up or North up. You can use the compass on the map to orient the map North up.

You can use your compass as a protractor to measure bearings on the map.

You can use your compass to measure distances on a map.

You can use the map and compass together to triangulate a position.
 
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adventureduo

Dave Druck [KI6LBB]
Doug, thank you for taking the time to post all this additional info up. You're greatly adding to the value of this post and we appreciate it very much.
See you all tonight!
 

adventureduo

Dave Druck [KI6LBB]
Last nights class was a great success and i can't wait to see what we learn tonight.

mapclass.jpg
 

clcoyle

Explorer
I would like to Thank Doug, Dave and everyone who helped put this Map and Compass together, I think it was a great sucesss and I enjoyed meeting everyone.

I can't wait to get out on the Trail with Map and Compass in hand and use all the skills to begin an adventure.

Thanks,

Christopher
 

nwoods

Expedition Leader
Class was fantastic. Doug was exceptionally well prepared and very knowledgeable with a great mentoring attitude. The maps and other training aide resources he had available were terrific, and the exercises were fun. I was shocked how fast the time flew.

Thanks Dave for your hospitality and organization of this event, and thanks Doug for your considerable time and expertise!
 

adventureduo

Dave Druck [KI6LBB]
Thanks for the kind words guys. Much appreciated feedback.. I want to thank everyone that came out and also thank Doug one more time for his time. The class was excellent and we're looking at doing another one in 2012. We'll keep you posted. The money that was collected will buy Raffle Tickets for the USFS OHV program ATV giveaway. That money goes back into the pot for the entire forest. If we end up winning the ATV, it will be returned. Thanks again everyone!
 

cnynrat

Expedition Leader
Kudos to FishPoet and AdventureDuo for making this happen. Many of us have become a little too reliant on GPS technology that doesn't always work as expected. Can't recall the last time the batteries died on my map or compass.

I looked through the syllabus and didn't see a topic that addressed what is perhaps the most challenging aspect of navigating with a paper map, which is of course getting the bloody thing folded correctly. ;)

Here's a little trick to deal with magnetic declination if you don't have a compass with that adjustment capability. At home, before you leave for your trip, take a long straightedge and use it to draw a series of lines at the angle of magnetic declination directly on your maps. I like to draw them at a spacing about equal to the width of the base of my compass. You'll end up with a series of diagonal lines on the map that are at magnetic north for that quadrangle, which can be used to orient the map easily when using a compass without declination adjustment. A little old school and low tech perhaps, but I used this approach for many years before I got a compass with adjustable declination.
 

nwoods

Expedition Leader
Here's a little trick to deal with magnetic declination if you don't have a compass with that adjustment capability. At home, before you leave for your trip, take a long straightedge and use it to draw a series of lines at the angle of magnetic declination directly on your maps. I like to draw them at a spacing about equal to the width of the base of my compass. You'll end up with a series of diagonal lines on the map that are at magnetic north for that quadrangle, which can be used to orient the map easily when using a compass without declination adjustment. A little old school and low tech perhaps, but I used this approach for many years before I got a compass with adjustable declination.

Doug showed us the trick that I had never known about regarding built-in adjustment that most compasses (but not the free KrackerJack kind) have. There is a small screw either on top or underneath (bottom of compass plate) of the bezel that allows you to crank in the necessary declination adjustment. I never knew about this, and man is it a time saver!

DeclinationScrew.jpg
 

cnynrat

Expedition Leader
Doug showed us the trick that I had never known about regarding built-in adjustment that most compasses (but not the free KrackerJack kind) have. There is a small screw either on top or underneath (bottom of compass plate) of the bezel that allows you to crank in the necessary declination adjustment. I never knew about this, and man is it a time saver!


Compasses with a built in declination adjustment are great, and I've been using a Silva Ranger for many years with adjustable declination. In times past not all compasses had that capability. Perhaps it's more common now.

There is another option besides a compass with adjustable declination or performing mental calculations.
 
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