Offroad Pics Video
 Articles & Info

 Project Jeep CJ-7

Reviews Great Products Tire Reviews Vendors

  Home Page
  Photo Album
  Tech Section
  Product Reviews
  Jeep Central
  Readers Rigs
  4x4 Club Links
  Links Directory
  4x4 Vendors
  Cool Products
  Shop for Junk
  Centralia PA
  Computer Help
  Site Index
  Project CJ-7
Jeep Project CJ-7

An ongoing Budgeted Rebuild/Build up of a Rock Crawling Machine.

Jeep Central
From Jeep History to Tech Specs and Projects.  This section is all about Jeeps.
Jeep Technical Info
Engine Swaps

Installing 23,000 Volt Offroad Lights

What are HID Lights?

Onboard Air
Converting a York
AC Compressor
to Pump Air

Warn 9500i Winch Installation

HEI Ignition
Installation & Review

Lockers, Limited Slips &
other Differentials Explained

Jeep Dana 300 TeraLow - 4:1 Gearset for the Dana 300 Transfer Case


Smoke rises out of the ground, the smell of sulfur is in the air, the ground collapses as homes are destroyed.
Science fiction?
Think again.


2007 Jeep Wrangler JK
Jeep Wrangler JK Specs

h3-2.jpg (10058 bytes)
Hummer H3

Jeep Commander Articles and Reviews

Jeep Grand Cherokee Articles & Reviews

Nissan XTerra Articles and Reviews

Jeep Grand Cherokee Articles & Reviews

Jeep Rubicon Articles and Reviews

Jeep Rubicon Unlimited Articles and Reviews

Suspension Lift Installations and Reviews





Understanding GPS Coordinates

*This is provided for general information purposes only.  How you choose to use the information is up to you.

GPS coordinates are commonly displayed as latitude and longitude.  This is not a projection to a Cartesian coordinate system (x, y grid) such as state plane or UTM, but an angular coordinate system.  Degrees of latitude and longitude measure the angle between a location and the reference line, namely the equator and Greenwich England.  The equator is a fairly obvious reference line as it creates a plane bisecting the globe half way between the North Pole and the South Pole.  It is relatively easy to locate since a person standing at the equator casts no shadow twice a year (vernal and autumnal equinox.  About March 21 and September 21).  Latitude is the angle formed by a line from the center of the earth to the equator and a line from the center of the earth to your location.  Latitude is zero at the equator, North (positive) 90 degrees at the North Pole, and South (negative) 90 degrees at the South Pole.

Longitude has a much more complicated history as it is far more difficult to determine without GPS.  Longitude is the angle formed by a line from the center of the earth to the prime meridian at Greenwich England and a line from the center of the earth to your location. (A meridian is a line of longitude running from pole to pole.)   Since the earth rotates 360 degrees each day, it is necessary to know the time very accurately in order to relate the location of the sun to this angle.  The English were very involved in shipping and development of an accurate, seagoing clock so that they could accurately calculate the correct longitude.  They chose to use the Royal Observatory at Greenwich, London, England for their reference meridian. (Visit for more information)  Longitude ranges from West (negative) 180 degrees to East (positive) 180 degrees. 

Latitude and Longitude are frequently recorded as degrees, minutes and seconds.  Ptolemy (about 150 AD) divided the degrees into 60 parts and those parts into 60 parts.  “In the Latin translation of the text these subdivisions became partes minutae primae and partes minutae secundae from whence our “minutes” and “seconds” of arc are derived.” (Brown, The Story of Maps, pg 60)  This can be cumbersome so you could use Decimal Degrees.  GIS systems need to use this simpler format.  This table below shows the precision of various units at the northern U.S. region.  Note that one degree of longitude is about 69 miles at the equator and 0 miles at the poles.  Latitude is always about 69 miles.




1 degree

69 miles

42 miles

1 minute

6072 ft

3696 ft

1 second

101.2 ft

61.6 ft




Decimal Degrees




36432 ft

22176 ft


3643.2 ft

2217.6 ft


364.32 ft

221.76 ft


36.43 ft

22.18 ft


3.64 ft

2.22 ft


4.37 In

2.66 In


0.44 In

0.27 In


Conversion from degrees, minutes, seconds to decimal degrees

118 degrees 8 minutes 26.2353 seconds West.  = -118.1406209154

118 +    8/60  +    26.2353/3600 = 118.1406209154 Make this negative if it is either west longitude or south latitude.

Conversion from decimal degrees to degrees, minutes, seconds

-118.1406209154 = 118 degrees 8 minutes 26.2353 seconds West

 W         If it is negative then it is either west longitude or south latitude.

 118       The degrees are left of the decimal place

8          Multiply the decimal portion (0.1406209154) by 60 to get decimal minutes (8.4372549).  The minutes are left of the decimal place.

 26.2353   Multiply the decimal portion (0.4372549) by 60 to get decimal seconds

Two common projected coordinate systems

State Plane and Universal Transverse Mercator (UTM) coordinate systems are commonly used in the GIS/GPS industry.  State plane coordinates are not usually used on personal GPS units as there are many separate State Plane coordinates systems and they vary enough that they can be difficult to explain.  UTM is commonly found on USGS Topographic maps so can be useful for outdoorsmen who are using these maps.  The units are meters from a reference point.   We are in UTM Zone 11 North.  Each zone covers 6 degrees of longitude.  Its origin is at the equator and its central meridian (Zone 11’s central meridian is 117 degrees W).  A false easting of 500,000 is used to make sure that all of the coordinates are positive.  Units will be X meters East and Y meters North. (Note that there are 3.2808 feet/meter)


The two most common datums in use today are WGS 84 (World Geodetic System of 1984. A geocentric datum and geographic coordinate system created by the United States military) and NAD83 (North American Datum of 1983. A geocentric datum and graphic coordinate system based on the Geodetic Reference System 1980 ellipsoid (GRS80). Mainly used in North America, its measurements are obtained from both terrestrial and satellite data.)  A less common datum is NAD27. (North American Datum of 1927. The primary local geodetic datum and geographic coordinate system used to map the United States during the middle part of the 20th century, referenced to the Clarke spheroid of 1866 and an initial point at Meades Ranch, Kansas. Features on USGS topographic maps, including the corners of 7.5-minute quadrangle maps, are referenced to NAD27. It is gradually being replaced by the North American Datum of 1983.)

Magnetic Declination

Magnetic Declination relates magnetic north (where a needle points) to true north (north pole).    You can go to the NOAA website to calculate the current declination for you area. Declination does change over time and varies by location. 


Some GPS units have a digital compass built in (expensive) and others use calculated bearing from GPS coordinates collected along your path (course you have been following, not necessarily where you are going, and NOT where the unit is pointing).   Using the compass on a GPS unit is often difficult to do well and thus ill advised.  A high quality option that is fairly easy to use (instructions included) is the Silva Ranger CLQ Sighting Compass with Quadrants Bezel.  This compass has a mirror and sighting notch to aid accurate sighting.  The quadrant bezel reads in units like you normally find on legal descriptions and in 2 degree increments for fine resolution.  There is also a geared adjustment of declination so that declination compensation becomes automatic and stable.  Price is around $60.

Wide Area Augmentation System (WAAS)

WAAS is a system for correcting GPS coordinates so that their accuracy is adequate for precision flight operations at airports.  The FAA is helping to develop this system and is now available on many GPS units that you buy over the counter.  Visit the FAA’s website to read more about it.   This is a relatively inexpensive feature that is highly recommended.


Related Information:

Understanding GPS Coordinates 
What is GPS and How Does it Work?

Offroad Tire Info
P-Metric Tire Sizes Conversion to Inches
Tire Terminology
Wheel Terminology
How to Pick the Right
Tires for your Truck
Truck Tire Info
Tire Sizes Clearance Chart
Tires - What Hits What Fits
All Terrain  Mud Terrain
Tire Reviews & Info
Mud Terrain MT Tire Reviews
All Terrain AT Tire Reviews
Super Swamper Bogger
Super Swamper SSR
Super Swamper SX
Super Swamper Vortrac
Interco IROK TSL
Super Swamper LTB
Super Swamper TSL
Super Swamper TSL Radial
Super Swamper Narrow
Interco SS-M16 Swamper
Thornbird TSl Radial
Thornbird TSl Bias
Thornbird TSL
Parnelli Jone Dirt Grip
BFGoodrich Krawler
BFGoodrich MT T/A KM
BFGoodrich MT T/A KM2
BFGoodrich AT TA KO
BFGoodrich Mud King XT
Bridgestone Dueler MT
Cooper Discoverer ST
Cooper Discoverer STT
Cooper Discoverer ST/C
Federal Couragia MT
Firestone Destination AT
Firestone Destination MT
General Grabber MT
General Grabber AT2
Green Diamond Icelander
Ground Hawg Mud Tire
Hankook Dynapro MT
Hankook Dynamic MT RT01
Hercules Terra Trac MT
Hercules Trail Digger MT
Kelly-Springfield Safari DTR
Kelly-Springfield Safari MSR
Kumho Road Venture MT
Kumho Road Venture KL71
Kumho Road Venture AT
Dick Cepek Mud Country
Dick Cepek F-C II
Dick Cepek Fun Country II
Dick Cepek Fun Country Nylon
Dick Cepek Fun Country Kevlar
Mastercraft Courser MT
Mastercraft Courser HTR
Mastercraft Courser HTR Plus
Maxxis BigHorn Radial
Maxxis Creepy Crawler
Maxxis Trepador
Maxxis Buckshot Mudder
Maxxis MA-SW
Maxxis M-8080 Mudzilla
Maxxis MT-754 Buckshot
Maxxis MT-753 Bravo
Maxxis MA-751 Bravo
Maxxis MA-S2 Marauder II
Maxxis MA-S1 Marauder
Maxxis MT-762 BigHorn
Nitto Mud Grappler
Nitto Trail Grappler MT
Nitto Terra Grappler
Nitto Dura Grappler
Nitto Dune Grappler
Nokian Vatiiva MT
Pit Bull Rocker Extreme
Pit Bull Maddog
Pit Bull Growler
Goodyear Wrangler MT/R
Pro Comp Xterrain
Pro Comp All Terrain
Pro Comp Mud Terrain
Pro Comp Xtreme AT
Pro Comp Xtreme MT
Toyo Open Country AT
Toyo Open Country MT
TrXus Mud Terrain
TrXus STS All Terrain
Michelin LTX A/T²
Michelin LTX AT2 Press
Michelin LTX AT2
Mickey Thompson MTZ
Mickey Thompson MTX
Mickey Thompson Baja Claw Radial
Mickey Thompson Baja Claw Bias
Mickey Thompson Baja Crusher
Mickey Thompson Baja ATZ Radial SLT
Competition Claw
Dunlop Mud Rover
Federal Couragia M/T
Nitto Dura Grappler
Yokohama Geolandar
Dick Cepek's 2008 F-250 Super Duty Project Vehicle – Project CRUSHER
Mud Tire Reviews

FJ Cruiser

Engine Specs
Drivetrain Specs
Photo Gallery
FJ Cruiser Tires
Press Releases & Specs
FJ Cruiser Reviews

Paragon Adventure Park
Rock Krawl

Thousands more
photos here..»


Off-Road Lights
by LightForce Product Review / Installation.
from Off-Road Lights


Black Diamond Suspension Lift instal

 for CJ-7

Ramp Travel Index
RTI / Ramp Travel Index What it is and how to calculate it, with and without the ramp.

Offroaders Guide to Gearing up for Offroad
From Basic Equipment to Well Equipped.  An extensive list guide to help you prepare your vehicle for the offroad.

Do it Yourself
Detriot EZ Locker Install  in a 92 Toyota 8" rear

For all the Jeep
Fans out there!

Department of Cheap Tricks and Useful Tips
Ultra-Cool Hand Throttle for Free!

Jeep V8 Swap Tips

The Exploding Clutch

Radiator Protection using 6 bucks worth of material

Cracked Under Pressure - Fixing a smashed fingernail

A Cheap, effective alternative to undercoating

Home-built Saginaw Gearbox Brace for the cost of lunch!

Ammo Box Storage - Mounting Them for Quick Disconnect

Home-built Serious Skid-Plate protection for the Oil Pan for under 20 bucks!


Building a Garage?
Need a Garage Plan?
Need a House Plan?

Knoebels Amusement Park