Navigating a Topograhic Map

Reviewing a topographic map is usually the starting point for the planning of any back country trip.  A topographic map is your road map to the outdoors.  It provides you detailed information at a scale that is meaningful and detailed.  For years, the US Geologic Survey (USGS) has been the principal publisher of accurate maps.  Within the last decade we have seen many innovations in mapping products that include new mapping companies and publishers, software, maps for the GPS, and “Apps” for the iPhone. Outdoor Quest/Blake Miller image Still, the USGS map remains the standard for back country navigation (visit the USGS’s site at www.topomaps.usgs.gov.)   I’d also recommend looking at June Fleming’s “Staying Found” or Bjorn Kjellstrom’s “Be Expert With Map & Compass.”  Once you develop a map foundation you will easily shift to many of the other products on the market today.  Many publications, videos, and web sites will give you a te rundown on the features, symbols and components to a map.  This article will discuss a few of the key features that you should be aware on a 7.5 minute map. ·         Contour Lines These are the thin brown lines that snake across the map.  Contour lines connect equal points of elevation such that every point on that line will be at that elevation above sea level.  Visually, the contour lines give you a mental three dimensional view of the terrain.  These lines provide a view of slope and pitch, depressions, ridge lines and level ground; the highs and lows of the earth’s surface.  Outdoor Quest/Blake Miller image  These lines provide shape and a sense of texture. There are two primary types of lines, index and intermediate lines.  Index lines stand out as they are a touch wider, a darker shade of brown and indicate the elevation with numbers such as 4500; the elevation is in feet.  Between the index lines are the thin intermediate line that are spaced uniformly and further define the elevation, slope and contour.  The intervals between the intermediate lines are specified at the bottom of the map adjacent to the scale data. ·     Scale Consider scale as your view of the map; it is like your “overhead zoom” setting.  To cut to the chase, a 7.5 minute map or quadrangle has a scale that is referred to as 1:24,000; where one inch is equal to 2000 feet.  It is your best source of information of the back country.  At this scale, the map has much more validity and provides more usable information for your backcountry planning.  You can view important landmarks, streams and geographic features.  To complete the navigation picture I always refer a second map, such as a map of the national forest (e.g., the Deschutes National Forest.)  Commonly, such a map will be “zoomed” way out and have a scale of 1:100,000 or 1:250,000.  Imagine that such a map would be made up of many 7.5 minute quadrangles. ·    North  Features on a map such as trails, roads, mountain peaks and streams are all laid out in relation to true North; the North Pole.  The north-south borders of the map and the small declination diagram are your best references for true North.  Other grid lines (such as the red Township, Section and Range lines) may not be aligned to true north at all.  Be careful of these lines should you need to triangulate your position on a map. ·    Declination This is the angular difference between true North and Magnetic North.  The red needle on your magnetic compass points to Magnetic North.  The accuracy of the information found in the Declination Diagram is dependent on the age of the map.  To get the latest declination for any area visit www.magnetic-declination.com. Personally I use a magnetic compass that I can adjust for declination; it just makes my navigation easier.  When adjusted, my compass provides bearing information in degrees true as does my map and my adjusted GPS. ·    Coordinates Latitude and Longitude (Lat/Long) are the familiar coordinate system to most outdoorsmen and women.  Coordinate data is found at the top and bottom corners of each map.  Lat/Long coordinate increments are also found every 2’ (minutes) and 30” (seconds) on the sides of the Map.  A scaling device is necessary to pull complete coordinates off a map; this is a pain. In the 1940’s a coordinate system know as Universal Transverse Mercator (UTM) was developed.  To keep a very long story short, your 7.5 minute map has a new grid laid over it, the grid dimensions are 1000 meters by 1000 meters.  For more complete   information on UTM grid visit the USGS’s web site UTM or Lathem’s “GPS Made Easy” (which is probably at your local library.) Simplicity is the essence of UTM.  Scouts, hunters and hikers have joined Search and Rescue (SAR) teams around the country in using this system.  Your GPS receiver can easily be switched to UTM from the set-up menu. ·    Bar Scales   Notice the bar scales at the bottom of the 7.5 minute map.  The scales provide measuring data in miles, feet and meters.   On the far left side of the meter scale, the scale is broken down into units of 100 meters, this applies directly to UTM. Notice on the scale bar (feet) that 1 inch equals 2000 feet. ·    Map Datum Information about map datum is found in the lower left corner of a 7.5 minute map.  I have found that the simplest definition from GPS maker Garmin is: “A math model which depicts a part of the surface of the earth. Latitude and longitude lines on a paper map are referenced to a specific map datum. The map datum selected on a GPS receiver needs to match the datum listed on the corresponding paper map in order for position readings to match.” The bottom line: most 7.5 minute maps are made to the North American datum of 1927 (NAD27 or NAD27 CONUS on your GPS).  New GPS receivers are set to datum WGS84.  The difference between the datum could be over 100 meters/yards.  The solution: When pulling points off a map shift your GPS’s datum to match the map.  If precision is not an issue for your outing don’t worry about datum. As you begin your trip planning don’t forget the magnetic compass, the important partner to any topographic map.  See Selecting a magnetic Compass for more information about buying a good compass.

Backstops for The Hiker and Hunter

A backstop keeps the hiker safe.  By using a natural and man made land features, a backstop keep the hiker in the right area.  Backstops are found by a careful study of a topographic map.

One feature every outdoorsman should pay attention to is called a “backstop.”   A  backstop is a boundary or a natural barrier that keeps one in their specified hiking area.  If a hiker goes beyond the backstop, then they will know they have gone too far.

When looking over a map of a hiking area, it is essential to understand the impact of terrain and land features.  Doing so will allow one to build an association of topography with a general lay of the land.  Key on natural and man-made features that includes roads, streams, buttes and buildings.  Take the time to really examine the map’s topography by studying the brown contour lines. This attention to detail will give the hiker a “feel” for elevation changes, shape and important land marks.  More importantly, it will allow the hiker to develop a mental map of the hiking area.  This concept lends itself to map training for those not backcountry experienced, and it is an excellent  teaching tool for children.

For example, in the image above ForestRd 32 serves as a backstop.  The hiker should remain west of ForestRd 32 because traveling east of 32 is hazardous due to the Swamp. Additionally, note that key terrain features associated with the trail include the river, mountains, a road and the swamp.

The example above is very simplistic but demonstrates the importance of having that “mental map”, especially if visibility becomes an issue.

The image above offers another example.

The map above is an area of steep terrain to the west, a lake to the east and trails surrounding most land features.  If the hiker planned to bushwack west of the campground (just below the larger lake) and hike in fairly flat terrain with gentle elevation changes, then the steep terrain to the west (Tam McArthur Rim) would be an excellent backstop. This is because it provides confirmation of the hiker’s general location. Care should be taken when using  trails that border Little Three Creek lake-note that the trail doesn’t continue west.  In such a situation, it is possible for the hiker to walk beyond the lake.

Backstops are another navigation tool that can keep the hiker in a safe location, and should be utilized as a visual resource.

More About Using a Topographic Map

Reviewing a topographic map is usually the starting point for the planning of any back country trip.  A topographic map is your road map to the outdoors.  It provides you detailed information at a scale that is meaningful and detailed.  For years, the US Geologic Survey (USGS) has been the principal publisher of accurate maps.  Within the last decade we have seen many innovations in mapping products that include new mapping companies and publishers, software, maps for the GPS, and “Apps” for the iPhone. Outdoor Quest/Blake Miller image Still, the USGS map remains the standard for back country navigation (visit the USGS’s site at www.topomaps.usgs.gov.)   I’d also recommend looking at June Fleming’s “Staying Found” or Bjorn Kjellstrom’s “Be Expert With Map & Compass.”  Once you develop a map foundation you will easily shift to many of the other products on the market today.  Many publications, videos, and web sites will give you a te rundown on the features, symbols and components to a map.  This article will discuss a few of the key features that you should be aware on a 7.5 minute map. ·         Contour Lines These are the thin brown lines that snake across the map.  Contour lines connect equal points of elevation such that every point on that line will be at that elevation above sea level.  Visually, the contour lines give you a mental three dimensional view of the terrain.  These lines provide a view of slope and pitch, depressions, ridge lines and level ground; the highs and lows of the earth’s surface.  Outdoor Quest/Blake Miller image  These lines provide shape and a sense of texture. There are two primary types of lines, index and intermediate lines.  Index lines stand out as they are a touch wider, a darker shade of brown and indicate the elevation with numbers such as 4500; the elevation is in feet.  Between the index lines are the thin intermediate line that are spaced uniformly and further define the elevation, slope and contour.  The intervals between the intermediate lines are specified at the bottom of the map adjacent to the scale data. ·     Scale Consider scale as your view of the map; it is like your “overhead zoom” setting.  To cut to the chase, a 7.5 minute map or quadrangle has a scale that is referred to as 1:24,000; where one inch is equal to 2000 feet.  It is your best source of information of the back country.  At this scale, the map has much more validity and provides more usable information for your backcountry planning.  You can view important landmarks, streams and geographic features.  To complete the navigation picture I always refer a second map, such as a map of the national forest (e.g., the Deschutes National Forest.)  Commonly, such a map will be “zoomed” way out and have a scale of 1:100,000 or 1:250,000.  Imagine that such a map would be made up of many 7.5 minute quadrangles. ·    North  Features on a map such as trails, roads, mountain peaks and streams are all laid out in relation to true North; the North Pole.  The north-south borders of the map and the small declination diagram are your best references for true North.  Other grid lines (such as the red Township, Section and Range lines) may not be aligned to true north at all.  Be careful of these lines should you need to triangulate your position on a map. ·    Declination This is the angular difference between true North and Magnetic North.  The red needle on your magnetic compass points to Magnetic North.  The accuracy of the information found in the Declination Diagram is dependent on the age of the map.  To get the latest declination for any area visit www.magnetic-declination.com. Personally I use a magnetic compass that I can adjust for declination; it just makes my navigation easier.  When adjusted, my compass provides bearing information in degrees true as does my map and my adjusted GPS. ·    Coordinates Latitude and Longitude (Lat/Long) are the familiar coordinate system to most outdoorsmen and women.  Coordinate data is found at the top and bottom corners of each map.  Lat/Long coordinate increments are also found every 2’ (minutes) and 30” (seconds) on the sides of the Map.  A scaling device is necessary to pull complete coordinates off a map; this is a pain. In the 1940’s a coordinate system know as Universal Transverse Mercator (UTM) was developed.  To keep a very long story short, your 7.5 minute map has a new grid laid over it, the grid dimensions are 1000 meters by 1000 meters.  For more complete   information on UTM grid visit the USGS’s web site UTM or Lathem’s “GPS Made Easy” (which is probably at your local library.) Simplicity is the essence of UTM.  Scouts, hunters and hikers have joined Search and Rescue (SAR) teams around the country in using this system.  Your GPS receiver can easily be switched to UTM from the set-up menu. ·    Bar Scales   Notice the bar scales at the bottom of the 7.5 minute map.  The scales provide measuring data in miles, feet and meters.   On the far left side of the meter scale, the scale is broken down into units of 100 meters, this applies directly to UTM. Notice on the scale bar (feet) that 1 inch equals 2000 feet. ·    Map Datum Information about map datum is found in the lower left corner of a 7.5 minute map.  I have found that the simplest definition from GPS maker Garmin is: “A math model which depicts a part of the surface of the earth. Latitude and longitude lines on a paper map are referenced to a specific map datum. The map datum selected on a GPS receiver needs to match the datum listed on the corresponding paper map in order for position readings to match.” The bottom line: most 7.5 minute maps are made to the North American datum of 1927 (NAD27 or NAD27 CONUS on your GPS).  New GPS receivers are set to datum WGS84.  The difference between the datum could be over 100 meters/yards.  The solution: When pulling points off a map shift your GPS’s datum to match the map.  If precision is not an issue for your outing don’t worry about datum. As you begin your trip planning don’t forget the magnetic compass, the important partner to any topographic map.  See Selecting a magnetic Compass for more information about buying a good compass. Visit www.caltopo.com for free topographic maps of the Continental US.  This is a super mapping program that you can use to explore your area and print them at home.

Wilderness Guide

The National Outdoor Leadership School's "Wilderness Guide" is a wonderful book to add to your backcountry library.

"The classic backpackers handbook - revised and updated with information anon new equipment and techniques-providing expert guidelines for backpackers, hikers, campers- anyone who loves the outdoors."

Author Mark Harvey is a NOLS instructor and  freelance writer.

This book is an excellent first step in the planning process for backcountry  travel.

Available at Amazon.

Magnetic Declination

“Declination: A Noun. The horizontal angle between the true geographic North Pole and the magnetic North Pole, as figured from a specific point on the Earth.” www.dictionary.com

 Declination is a term that causes “brain cramps” for many of my students in my map and compass classes. When I mention Magnetic Declination eyes roll.

The web site www.magnetic-declination.com has an excellent discussion of what declination is and what causes it:

“Magnetic declination varies both from place to place, and with the passage of time. As a traveler cruises the east coast of the United States, for example, the declination varies from 20 degrees west (in Maine) to zero (in Florida), to 10 degrees east (in Texas), ......the magnetic declination in a given area will change slowly over time, possibly as much as 2-25 degrees every hundred years or so.......... Complex fluid motion in the outer core of the Earth (the molten metallic region that lies from 2800 to 5000 km below the Earth's surface) causes the magnetic field to change slowly with time."

Land navigation is based on the relationship to the North Pole; also known as “true north.  The measure of degrees of direction in relation to true north is called “degrees true.”  Maps are laid out in degrees true.  Land features (buttes, mountains, streams) on a topographic map are in reference to degrees true.  By that I mean the bearing from one mountain peak to another will be referenced in degrees true.  The map below illustrates that point. 

Magnetic compasses do not point to true north (the North Pole); the magnetic needle points to an area that could be considered the magnetic North Pole. 

As illustrated below, declination data can be found in the diagram at the bottom of a USGS topographic map, (on some commercially produced maps it can be hard to find.) 

Because declination changes over time, I recommend that map declination information be verified at www.magnetic-declination.com.   This is essential in the Pacific Northwest where maps are notoriously out of date in terms of road,  and city data.

So, how do we make this simple?  How do we convert magnetic to degrees true?

I could do the math.  In Oregon, where I live, the magnetic declination is 15.6° East declination.

My recommendation: have the compass do the work so that there is no confusion with the math.

To do this, I need to choose a compass that can be adjusted for declination.  Some examples are the Silva Ranger or the Suunto M3.

With one of these compasses, the compass dial or housing is adjusted and rotated manually.  Both the Suunto and Silva Ranger come with a small, flat adjusting tool.  Consult with owner’s manual that came with the compass.

If declination is Easterly (Western U.S.) I will rotate the dial causing the baseplate’s orienting arrow to move in a clockwise direction.

   If declination is Westerly (Eastern U.S.) I will rotate the dial causing the baseplate’s orienting arrow to move in a counter-clockwise direction.

Now, adjust the dial and align the red magnetic needle on top of the orienting arrow (the red arrow engraved on the baseplate) the compass will provide directions in degrees true.

Managing Your GPS Waypoints

Outdoor Quest //Blake Miller image  Lots of things can happen to a GPS Waypoint or data file.  You can put data in. You can take data out.  You can lose it (the GPS breaks or the wrong button entry is selected.)  But be careful, far worse, too much data can make your navigation difficult.  In my land navigation class I stress keeping your navigation simple.  Frequent and simple Waypoint management is essential to GPS use.  When it’s time to return to the truck, it should be obvious what GPS Waypoint to select.   Dump the junk before the start of a trip.  As you leave the trail head your GPS should have only necessary data saved on your GPS.  That Waypoint for the fishing hole is important but needs to be saved elsewhere.  Start by deleting Waypoints that really are not needed.  Free those data bites to the atmosphere.  To save your “got to have, must save Waypoints:”               1.            Use Garmin’s “Trip and Waypoint Manager.”  It probably came with your GPS.  It can also be purchased from Garmin for about $30.00; www.garmin.com.  Down load those Waypoints to your PC.  2.            If you don’t have the Garmin program, consider “Easy GPS.”  It is free and available at www.easygps.com.             3.            Log the important data in a notebook.  Electronic storage allows you to save Waypoints and track data (that bread crumb trail on your map screen.)  Further, you can upload old Waypoints another day for a trip to that special fishing spot.  This data can also be down loaded into your friends GPS too.  It can also be uploaded to your new GPS in the future.  Remember though; when you receive or transfer GPS Waypoint data always verify that you have the compatible map datum and coordinate system set on your receiver.  Finally, give important Waypoints a name.  It’s easier to remember a GPS Waypoint named “CAMP” instead of 21 (or was it 25.)

UTM Grid For The Hiker

Universal Transverse Mercator (UTM) is a grid system that describes a person’s geographic location in the backcountry.  It is simple to understand and use because:

1.    It is intuitive -  it’s concepts can be understood quickly,

2.    It can be easily self taught,

3.    Young hikers grasp this system easily,

4.    A location on a map can be quickly determined, and;


5.    It is a selection option for Global Positioning System (GPS) receivers.  

A navigation grid is a reference system developed by cartographers that can be used to plot a geographic position on a map.   There are many grid systems available for use such as Latitude and Longitude and Universal Transverse Mercator (UTM).  Several countries have their own national grid system. 

The UTM system is just like a Cartesian Grid.  For example, the grid position below is just 2.2 units over and 2 units up.

 To understand the complete grid we will start by observing that the globe is divided into 60 zones.  Each zone is 6° of longitude wide.  Each zone runs north and south; 84° north to 80° south.

The image below highlights the UTM zones in the continental United States.

UTM grid consists of Northings and Eastings.  The image below highlights the complete layout of a UTM zone.  Notice the Central Meridian that runs north and south through the zone.  Like longitude, this meridian runs from pole to pole.  All values for measuring position are in meters.  At the equator the zone is 500,000 meters wide.  The width of the zone is described by Eastings.  Northings run north or south from the equator; again all values are in meters.

UTM coordinates are presented such that the zone is listed first, followed by the Easting and then the Northing.

                                    10   0524120 E  4891555 N

The hiker should think of a grid as a series of defined squares on a map (see below.)  On a 1:24,000 scale (7.5 minute topographic quadrangle) the grid lines are 1000 meters apart; north or south the spacing between grid lines is 1000 meters.

The coordinate values are known Easting’s (vertical lines) and Northing’s (horizontal lines.)

Easting values increase moving from left to right and Northing’s increase from bottom to top.  Coordinate values are always positive.

 Every location will have a zone identifier.  On the map above the zone is linked to the Easting value and is the first set of numbers.  In this case the zone identifier is the number 10. 

 

 The letter “T” seen above is a secondary, horizontal (east-west) identifier.  I personally pay little attention to it in my backcountry trips.

All USGS maps identify the zone in the title block at the bottom left of the map.  Note that on some commercial maps the UTM zone identifier may not be in the title block and can be hard to find.

The UTM coordinate can now be refined to a meter.  Again the spacing between the grid lines is 1000 meters (1 kilometer).  On the maps below, the tick marks between gridlines are in increments of 100 meters.  The hiker can then interpolate the distance between the tick marks.  

The position of the large X on the map above would be described as:

            10 5 25 270 East (the green line)

            47 91 180 North (the red line)

The final three places will always be expressed (10 5 25 270 East.)  The value 2 is in units of hundreds, the 7 is in units of 10 and the 0 is in units of 1’s.   Thus, 50 meters would be written as 050. 

Every point on a map (e.g., a mine, an intersection, a camp site, etc) can be described using UTM coordinates to the accuracy of one square meter.

I recommend consider carrying a small plastic ruler or other suitable straight edge when accuracy is important.  For general hiking and backpacking, one can quickly estimate a current position in the backcountry without other map tools.

UTM coordinates of a destination taken from a map can be easily saved on a GPS receiver.  For example, to do this the hiker “marks” a waypoint and then moves the backlit bar (yellow shaded area) from “save” to the “location” data field.  The “location” data field is then edited per the receiver’s instruction manual.

  

A fine reference for more practical information about UTM grid is Lawrence Latham’s book GPS Made Easy.  Chapter 5 has an easy to understand tutorial on this grid system; that’s how I learned it.