It is important to learn these other tools because GPS receivers are electronic, and like any other form of electronics, they are prone to failure or dead batteries.  You would not stake your life on a cordless phone or computer hard drive right?  So do not put that kind of burden on your receiver.  The traditional methods of navigation are an alternative to using GPS, but more importantly, they enhance the operation of GPS, allowing the equipment to be used to its fullest capability.  First are the basics on maps and compass reading, then we will combine map, compass and GPS for a trip to the historical Bohemia mining distric.

Navigation 104, Paper or Electric?

Map Basics

MAP SCALES

1:500,000                              1 inch  =  8 miles

1:250,000                              1 inch  =  4 miles

1:150,000                              1 inch  =  2.4 miles

1:62,000  (15 minute)           1 inch  =  1 mile

1:24,000  (7.5 minute)          1 inch  =  20,000 feet

Seven and a half minute maps are not practical for cross-country travel, but ideal for when detail is required to travel into more remote wilderness areas.  United States 7.5 Minute maps are made and updated by the U.S. Geological Survey.  They can be purchased for about $4.00 at outdoor stores or from the Government over the phone.

For our trip to the Bohemia mining district we purchased at 7.5 Minute Topo map titled Fairview Peak Quadrangle-Oregon.  The bottom section of the map gives its details which includes the following:

Map Date:  Produced in 1986, and updated in 1997.  Topo info from 1980.

Datum:  North American Datum of 1927 (NAD 27).  This is important because out GPS receiver will have to be set to this datum if not defaulted to in anyway.  This is done on most receivers by selecting the datum options under a set up menu. 

Declination Diagram:  The scale indicating the degree a compass is adjusted to correct magnetic north to true north.  This maps declination is 17.5 degrees.

Map Scale:  1:24,000, one inch equals 24,000 inches on the ground.

Mileage scale:  One mile equals about 2-5/8 inches.

Contour Interval:  The elevation lines are 40’ apart, every 5^th darker brown line indicates the elevation in feet.

Misc. Information:  Where this map is in relationship to the state, map names surrounding this map, and list of symbols for highways and roads.

Another advantage of 7.5 Minute maps is that they include the two main types of coordinates.  Most maps are formatted with Latitude/Longitude.  These maps also include Universal Transverse Mercator (UTM) coordinates. 

Map Coordinates Includes Lat/Long and UTM 4818  UTM Northing 4817000mN  Full UTM Northing 529000mE  Full UTM Easting  (lower left) 43° 30’  43 Degrees Latitude 122° 37’ 30”  122 Degrees Longitude  (lower right)

There are a number of map coordinates but the primary two are Latitude/ longitude and Universal Transverse Mercator (UTM).  Most North American GPS units are programmed to default to Latitude/Longitude.  UTM coordinates can be selected by the set up menu.  Either system provides a numeric set of coordinates in either degrees or meters, for any location in the world.  Here are the basics on each system.

Latitude/Longitude

Latitude lines run horizontally around the globe and parallel the earth’s equator, being the staring point at zero degrees.  The equator also splits the globe in north and south hemispheres.  Lines run horizontally to 90 degrees at the north and south poles.  They measure north-south coordinates.

Longitude lines circle the globe vertically intersecting the north and south poles to measure east-west coordinates.  The starting point is zero degrees at Greenwich, England, and wrap around the earth east and west to 180 degrees. 

Each degree equals 69.05 miles.  For greater detail, degrees are split into minutes and seconds.  One degree equals 60 minutes, each minute equals 60 seconds.

1° = 60’ (minutes), 1’(minute) = 60” (seconds). 

That is how Latitude/Longitude coordinates are written:

Degrees°      Minutes’        Seconds”

122° 37’ 30” or with a decimal point 122° 37.50’ or 122.6250°

(All three are the same location.)

One degree = 69.05 statute (ground) miles

One minute = 1 nautical mile or 1.15 statute miles

One second = 100 feet

This applies to Longitude distances only at the equator.  The length in the Longitude lines between the Meridians (vertical Latitude lines), decrease as they approach the north and south poles.

Here are the coordinates for Sunriver, Oregon:

                        N 43° 52’ 35”,   W 121° 27’ 10”

                                                or

                        N 43° 52.589’,     W 121° 27.170’

Latitude is listed first, measuring the north-south position.  This address is north of the equator by 43 degrees, 52 minutes and 35 seconds, or (52.589 minutes.)

Longitude is listed second, measuring the east-west position.  This address is west of Greenwich, England by 121 degrees, 27 minutes and 10 seconds, or (27.170 minutes.)

For more information on reading latitude/longitude coordinates, see chapter 106.

Universal Transverse Mercator (UTM).

This system is gaining popularity fast and will most likely be the standard in the future.  It utilizes kilometers and meters instead of degrees and seconds.  Using the metric system allows reasonably accurate coordinates to be estimated from a map without the use of a ruler.

The UTM world grid divides the globe into 60 equal sections called Zones, 6 degrees apart.  Each Zone is labeled 1 through 60 beginning at 180° Longitude, wrapping around the globe to the east.  This system does not include the north and south poles, requiring the Universal Polar Stereographic (UPS) grid system to cover these areas.

Each 6° Zone has horizontal and vertical reference lines.  A vertical line known as the Zone Meridian splits the section into two 3° halves.  Vertical and horizontal grid lines are 1000 meters or 1 kilometer apart.  Coordinates indicate the number of meters east from the beginning zone line, (Easting), and how many meters north or south from the equator, (Northing).

Easting is the horizontal, east/west measurement that indicates the number of kilometers/meters the coordinate is east from the start of the zone line.  The numbers increase moving left to right, west to east.  Each zone’s meridian begins with 500000.

Northing is the vertical, north/south measurement that indicates the number of kilometers/meters the coordinate is north or south of the equator.  The number at the equator in the Northern Hemisphere is 0000000.  This number increases moving north.  In the Southern Hemisphere, the number at the equator begins with 10000000, and decreases moving south.

Here are the UTM coordinates for Sunriver, Oregon:

10 T    0624301  E

            4859317  N

This is how UTM coordinates are broken down:

·        (10) indicates the coordinates are in the 10^th world zone.  Note on the above world graph, this vertical zone covers the Western United States.

·        (T) indicates the world zone designator.  Note on the above world graph, this horizontal zone covers the Northern United States.

·        (0624301) is the Easting as indicated by the (E) at the end of the number. Each zone’s meridian begins with 500000, therefore this location is 124,301 meters, or 124.3 kilometers east of the zone’s meridian.

·        (4859317) is the Northing as indicated by the (N) at the end of the number.

Knowing that the number at the equator in the Northern Hemisphere is 0000000.  This location is 48,559,317 meters, or 4,859.3 kilometers north of the equator.

The larger two numbers are called the “Principal Digit.”  These correspond with the coordinates that run along the top, bottom, and sides of the map.  The principal digit numbers are one kilometer, or 1000 meters apart.  This is what makes UTM coordinates easier to read, knowing that map grid lines are in 1000 meter blocks.  Points on a map can be selected by site, with accuracy within 50 meters without the use of a ruler.

TIP:     Fortunately using UTM coordinates on a map is much simpler than trying to explain it.  The main thing to remember is grid lines are 1000 meters apart.  It can be confusing mixing the metric system and miles.  Remember a meter is just longer that a yard, (39.37 inches), and 1000 meters, (a kilometer) equals .62 of a mile.

See chapter 106 for more information on reading UTM coordinates, and how to read topographical maps.

TIP:     UTM is the easiest to use, but Latitude/Longitude is still the most common in the United States.  Before selecting a coordinate system, consider the area and what maps are available.  Also consider whom the information will be used with.  If working with a group such as a race team or search and rescue, find out what others are using to ensure you speaking the same navigational language.

Electronic Maps

Maps have gone high tech too, but don’t throw out your paper maps yet.  There are many sources for electronic maps that include online map services and mapping software.

Online electronic map services offer the ability to conduct an Internet search to obtain a map of an area of interest.  These services are free, and are very helpful by providing quick and reasonably accurate mapping information.  Many of these services also offer route features that provide directions with turn and distance information to reach the desired destination.

The route features work great as a quick reference on how to get from here to there.  Finding an address can be as easy as typing it into a map service search engine, then waiting for directions.  Out of town friends will be impressed when telling them directions of how to reach their house you have never been to before.  Well maybe, they are not always that accurate, but the information available is helpful, impressive, and will at least get you in the general direction.

This topo map of the Tillamook, Oregon area was located from Topozone.com.  Locating and printing topo maps from the web is very helpful, considering it is difficult to locally purchase detailed maps of distant locations.

For more information about online map services, check out our Map Resources section of Links Page.

There are also many types of map software that comes in one of two categories.  Traditional map manufacturers like Rand McNally and DeLorme, make their maps available on CD ROM, to be used on a computer, laptop or palm device.  They work great for planning trips as well as establishing or organizing waypoints and routes.  The maps can be printed out, but interaction with a GPS receiver can be limited.  For example, with a computer cable, waypoints can be transferred to and from the GPS receiver and the software, but the software’s actual mapping date cannot be uploaded to the GPS receiver to enhance the unit’s existing basemap. 

Garmin’s Mapsource CD-ROM provides good basic map detail of the world, including this area of Los Cabos, Baja, Mexico.

The second map software category is the proprietary mapping data provided by the GPS manufacturers.  Each major brand provides their own mapping software to work exclusively with there own GPS units.  Additional map detail can be purchased to enhance the unit’s own basemap.  For example, topographical or nautical information can be purchased and uploaded to the receiver.  Like the aftermarket software provided by the traditional map suppliers, this software can also be used on a PC for organizing trips, waypoints and routes.  Electronic maps can be printed and are an excellent resource to know the correct paper maps to purchase if additional detail is needed.

Using Garmin’s Mapsource program, a tracklog and waypoints were transferred from the GPS receiver to the computer mapping program.  This saved information provides a good history of where you have been, allowing the trip to be easily duplicated and shared with others.

For more information on how to purchase mapping software, please check out our upcoming Part two of our Buyer’s Guide.  For more information about using GPS with computers, check out our upcoming Navigation 107, “Using GPS with Computers.”

TIP:     Need more map detail?  Take a tip from the CIA and order aerial photography.  Aerial photos are often available in large scales such as 1:24,000.  Photos may be able to be enlarged for greater detail.  Most photos sold to the public are taken by private companies on government contract. Get out your checkbook and check in Yellow pages.

First Edition Revised January 2001.
Copyright, All rights reserved 2001

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