Back to school to lean
how to use GPS
By Jack W. Peters
For as many
luxuries as GPS provides, one is not the ability to toss out the traditional
map and compass.Â Getting
lost is inconvenient at best and terminal at worst.Â So do not stake your
life on your GPS alone.Â It is used optimally in conjunction with other
navigation tools such as: maps, compass, altimeters, pedometers, watches
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.Â
You would not stake your life on a cordless phone or computer hard drive
right?Â So do not put that kind of burden on your receiver.Â 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.Â 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?
come in a number of different scales, but when its time to get serious,
the greater the detail the better.Â The state road map kept in the glovebox
might be a 1:500,000 scale.Â Used as a highway reference where the entire
state fits on one side.Â The scale rating on this map is one inch equals
500,000 inches on the ground (approximately 8 miles).Â The most detailed
standard map used in the backcountry is the 7.5 Minute Topo. These highly
detailed maps are produced by the U.S. Geological Survey (USGS), and have
a scale of 1:24,000, where 2 5/8 inches equals one mile.Â They are 6.5
miles wide, 8.5 miles long, and cover approximately 55 square miles.Â
Topo stands for topographical which provides a 3-D prospective
of the ground.Â This is done with contour lines that indicate elevation.
1:500,000Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
1 inchÂ =Â 8 miles
1:250,000Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
1 inchÂ =Â 4 miles
1:150,000Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
1 inchÂ =Â 2.4 miles
(15 minute)Â Â Â Â Â Â Â Â Â Â 1 inchÂ =Â 1 mile
(7.5 minute)Â Â Â Â Â Â Â Â Â 1 inchÂ =Â 20,000 feet
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.Â United States 7.5 Minute maps are made and updated by the U.S.
Geological Survey.Â They can be purchased for about $4.00 at outdoor stores
or from the Government over the phone.
our trip to the Bohemia mining district we purchased at 7.5 Minute Topo
map titled Fairview Peak Quadrangle-Oregon.Â The bottom section
of the map gives its details which includes the following:
Map Date:Â Produced in
1986, and updated in 1997.Â Topo info from 1980.
Datum:Â North American
Datum of 1927 (NAD 27).Â This is important because out GPS receiver
will have to be set to this datum if not defaulted to in anyway.Â This
is done on most receivers by selecting the datum options under a set up
Declination Diagram:Â The
scale indicating the degree a compass is adjusted to correct magnetic
north to true north.Â This maps declination is 17.5 degrees.
Map Scale:Â 1:24,000, one
inch equals 24,000 inches on the ground.
Mileage scale:Â One mile
equals about 2-5/8 inches.
Contour Interval:Â The
elevation lines are 40â apart, every 5th darker brown line
indicates the elevation in feet.
Misc. Information:Â Where
this map is in relationship to the state, map names surrounding this map,
and list of symbols for highways and roads.
advantage of 7.5 Minute maps is that they include the two main types of
coordinates.Â Most maps are formatted with Latitude/Longitude.Â
These maps also include Universal Transverse Mercator (UTM) coordinates.Â
Lat/Long and UTM
4818Â UTM Northing
4817000mNÂ Full UTM Northing
529000mEÂ Full UTM EastingÂ (lower
43Â° 30âÂ 43 Degrees Latitude
122Â° 37â 30âÂ 122
Degrees LongitudeÂ (lower right)
are a number of map coordinates but the primary two are Latitude/ longitude
and Universal Transverse Mercator (UTM).Â Most North American GPS units
are programmed to default to Latitude/Longitude.Â UTM coordinates can
be selected by the set up menu.Â Either system provides a numeric set
of coordinates in either degrees or meters, for any location in the world.Â
Here are the basics on each system.
lines run horizontally around the globe and parallel the
earthâs equator, being the staring point at zero degrees.Â The equator
also splits the globe in north and south hemispheres.Â Lines run horizontally
to 90 degrees at the north and south poles.Â They measure north-south
lines circle the globe vertically intersecting the north and south poles
to measure east-west coordinates.Â The starting point is zero degrees
at Greenwich, England, and wrap around the earth east and west to 180
degree equals 69.05 miles.Â For greater detail, degrees are split into
minutes and seconds.Â One degree equals 60 minutes, each
minute equals 60 seconds.
1Â° = 60â (minutes), 1â(minute) = 60â (seconds).Â
That is how Latitude/Longitude coordinates are written:
DegreesÂ°Â Â Â Â Â MinutesâÂ Â Â Â Â Â Â
37â 30â or with a decimal point 122Â°
(All three are the same location.)
One degree = 69.05 statute (ground) miles
One minute = 1 nautical mile or 1.15
One second = 100 feet
applies to Longitude distances only at the equator.Â The length in the
Longitude lines between the Meridians (vertical Latitude lines), decrease
as they approach the north and south poles.
are the coordinates for Sunriver, Oregon:
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
52â 35â,Â Â W 121Â°
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
52.589â,Â Â Â Â W 121Â°
is listed first, measuring the north-south position.Â This address is
north of the equator by 43 degrees, 52 minutes and 35 seconds, or (52.589
is listed second, measuring the east-west position.Â This address is west
of Greenwich, England by 121 degrees, 27 minutes and 10 seconds, or (27.170
more information on reading latitude/longitude coordinates, see chapter
Universal Transverse Mercator (UTM).
system is gaining popularity fast and will most likely be the standard
in the future.Â It utilizes kilometers and meters instead of degrees and
seconds.Â Using the metric system allows reasonably accurate coordinates
to be estimated from a map without the use of a ruler.
UTM world grid divides the globe into 60 equal sections called Zones,
6 degrees apart.Â Each Zone is labeled 1 through 60 beginning at 180Â°
Longitude, wrapping around the globe to the east.Â This system does not
include the north and south poles, requiring the Universal Polar Stereographic
(UPS) grid system to cover these areas.
has horizontal and vertical reference lines.Â A vertical line known as
the Zone Meridian splits the section into two 3Â° halves.Â Vertical and horizontal
grid lines are 1000 meters or 1 kilometer apart.Â 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.Â The numbers increase
moving left to right, west to east.Â Each zoneâs meridian begins with
Northing is the vertical,
north/south measurement that indicates the number of kilometers/meters
the coordinate is north or south of the equator.Â The number at the equator
in the Northern Hemisphere is 0000000.Â
This number increases moving north.Â In the Southern Hemisphere, the number
at the equator begins with 10000000, and decreases moving south.
are the UTM coordinates for Sunriver, Oregon:
TÂ Â Â 0624301Â E
Â Â Â Â Â Â Â Â Â Â Â
is how UTM coordinates are broken down:
(10) indicates the coordinates are in the 10th
world zone.Â Note on the above world graph, this vertical zone covers
the Western United States.
(T) indicates the world zone designator.Â 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 zoneâs meridian begins with 500000, therefore this location is 124,301
meters, or 124.3 kilometers east of the zoneâs 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.Â This location is
48,559,317 meters, or 4,859.3 kilometers north of the equator.
larger two numbers are called the âPrincipal Digit.âÂ These correspond
with the coordinates that run along the top, bottom, and sides of the
map.Â The principal digit numbers are one kilometer, or 1000 meters apart.Â
This is what makes UTM coordinates easier to read, knowing that map grid
lines are in 1000 meter blocks.Â Points on a map can be selected by site,
with accuracy within 50 meters without the use of a ruler.
Â Â Â Fortunately using UTM coordinates on a map is much simpler than trying
to explain it.Â The main thing to remember is grid lines are 1000 meters
apart.Â It can be confusing mixing the metric system and miles.Â Remember
a meter is just longer that a yard, (39.37 inches), and 1000
meters, (a kilometer) equals .62 of a mile.
chapter 106 for more information on reading UTM coordinates, and how to
read topographical maps.
TIP:Â Â Â Â
UTM is the easiest to use, but Latitude/Longitude is still the most common
in the United States.Â Before selecting a coordinate system, consider
the area and what maps are available.Â Also consider whom the information
will be used with.Â 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.
have gone high tech too, but donât throw out your paper maps yet.Â There
are many sources for electronic maps that include online map services
and mapping software.
electronic map services offer the ability to conduct an Internet search
to obtain a map of an area of interest.Â These services are free, and
are very helpful by providing quick and reasonably accurate mapping information.Â
Many of these services also offer route features that provide directions
with turn and distance information to reach the desired destination.
route features work great as a quick reference on how to get from here
to there.Â Finding an address can be as easy as typing it into a map service
search engine, then waiting for directions.Â Out of town friends will
be impressed when telling them directions of how to reach their house
you have never been to before.Â 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.
topo map of the Tillamook, Oregon area was located from Topozone.com.
Â Locating and printing topo maps from the web is very helpful, considering
it is difficult to locally purchase detailed maps of distant locations.
more information about online map services, check out our Map
section of Links Page.
are also many types of map software that comes in one of two categories.Â
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.Â
They work great for planning trips as well as establishing or organizing
waypoints and routes.Â The maps can be printed out, but interaction with
a GPS receiver can be limited.Â For example, with a computer cable, waypoints
can be transferred to and from the GPS receiver and the software, but
the softwareâs actual mapping date cannot be uploaded to the GPS receiver
to enhance the unitâs existing basemap.Â
Garminâs Mapsource CD-ROM provides
good basic map detail of the world, including this area of Los Cabos,
second map software category is the proprietary mapping data provided
by the GPS manufacturers.Â Each major brand provides their own mapping
software to work exclusively with there own GPS units.Â Additional map
detail can be purchased to enhance the unitâs own basemap.Â For example,
topographical or nautical information can be purchased and uploaded to
the receiver.Â 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.Â Electronic maps can be printed and are an excellent
resource to know the correct paper maps to purchase if additional detail
Garminâs Mapsource program, a tracklog and waypoints were transferred
from the GPS receiver to the computer mapping program.Â This saved information
provides a good history of where you have been, allowing the trip to be
easily duplicated and shared with others.
more information on how to purchase mapping software, please check out
our upcoming Part two of our Buyerâs
Guide.Â For more information about using GPS with computers,
check out our upcoming Navigation 107, âUsing GPS with Computers.â
TIP:Â Â Â Â
Need more map detail?Â Take a tip from the CIA and order aerial photography.Â
Aerial photos are often available in large scales such as 1:24,000.Â Photos
may be able to be enlarged for greater detail.Â Most photos sold to the
public are taken by private companies on government contract. Get out
your checkbook and check in Yellow pages.
Edition Revised January 2001.
Copyright, All rights reserved 2001