GEOLOGYCMU

Bill PalmerLecture 11

Topo Maps

GEOLOGY

Topo MapsA two-dimensional representation of a three-

dimensional land surfaceUse Contour lines to show reliefUseful to geologist and hunters, hikers, campers,

developers, etc.Also known as Quadrangle maps as they have four

sides

GEOLOGY

Topo MapsNorth is at topLook at key to tell difference between true north and

magnetic north.Declination is degrees between N and Magnetic NSymbols-look at handout for standard symbolsGreen=ForestPurple=photo revision

GEOLOGY

Topo MapsContour lines-brown squiggly lines that connect points

of equal elevationUsually 20 intervals in MODark brown line = 100 ft interval in MO (index

contours) In mountains, interval ma be greater; in sea level states,

interval may be less

GEOLOGY

Topo MapsContour lines rarely ever cross-Overhanging cliff or

rock bridgeThe closer contour lines, the steeper the landscapeThe farther apart contour lines, the flatter the landscape“Vs” in contour lines point uphillYou can interpolate between contour lines to determine

elevation of a specific point

GEOLOGY Topo Maps BM indicates a benchmark-an actual marker that gives the

elevation XBM 463 indicates that there is a marker (usually Bass)

there that gives the elevation These BMs are used for surveys Gradient is a measure of how steep a slope is, usually

given in ft/mile (25ft/mile) this would be a very steep white water river. MO river is about 4ft/mile

GEOLOGY Topo Maps

Scale is given as 1:24,000 this would mean that 1 inch on the map would be equal to 24,000 inches on the land

This also means that 1 foot on the map equals 24,000 feet on the ground

Not a convenient scale but in reality, when converted 1 inch = 2,000 feet at this scale so 1 inch on map is

about 6 2/3 football fields Check scale on bottom of map

GEOLOGY Topo Maps

Public Land SurveyBegan in 1700sDivided country into a grid of 6x6 milesMost states follow-in SW Spanish land grants usurpN-S are TownshipsE-W are RangeSo any square can be described by its T and RT4S R2W (Township 4 South and Range 2 West)

GEOLOGY Topo Maps

There are 6X6 or 36 section in each Township and Range

Sections are numbered 1-36 beginning in the upper right hand corner.

Any point can be determined in a section by dividing the section into 1/4ths, then 1/4ths, then 1/4ths, etc.

So a location might be the NW ¼ of the NW ¼ of the NW ¼ of Sec. 5 of T 5 N and R 21 W

You can be as detailed as you want

GEOLOGY Topo Maps

Sometimes you use ½ths. A section is 640 acres.A quarter section is 160 acresA square ¼ mi X ¼ mi is 40 acres.

GEOLOGY GPS

GPS is Global Positioning Satellites28 satellites are 12,000 miles above earthThey send a signal to a GPS receiverOriginally used by military for bombing, missiles, etc.Now can be used by public freePublic systems are less accurate than militaryMilitary systems =millimeters; public systems = feetGPS receivers cost as little as $100 up to what ever you

want to pay

GEOLOGY GPS

Most GPS receivers are 12 channel meaning the can receive signals from 12 satellites

GPS receivers must have 4 satellites to determine a point

GPS also needs an unobstructed sky. Won’t work indoors

Trees, Canyons, buildings will obstruct the signal

GEOLOGY

GEOLOGY UTM

GPS systems use the UTM measurement system-Universal Transverse Mercator System

UTM does not use degrees but rather a grid system that is measured in decimal-based metric units

UTM is based on 60 North-South zones numbered from 0 to 60 (each is 6 degrees)

A point is described by its Easting coordinate –the distance in a zone measured from West to East and a Northing coordinate or the distance from the equator

GEOLOGY UTM

To keep from using negative numbers in the southern hemisphere, the equator is given the nothing of 10,000,000 meters

The earth is divided into zones that go East-West that are 6 degrees apart (most of MO is in Zone15)

A GPS location might be given as:E384333 and N4455250 This would be 384333 meters East of the west edge of

zone 18 and 4455250 meters north of the equator

UTM ZONES

UTM GRIDS

GEOLOGY UTM

Info on Topo map margins gives the UTMTherefore,a hiker can use both a GPS and a Topo map

when hikingSome GPS units can incorporate a Topo map so a hiker

can see exactly where they areAll of this sounds complicated but in actuality it is

easier to use than describe

GEOLOGY Compass Bearings

A bearing is a compass direction from one point to another point

It may be expressed as an azimuth bearingNorth=0 degreesEast=90 degreesSouth=180 degreesWest=270 degrees

A circle has 360 degreesAzimuths are often used in Geology to describe a

direction

Geology

GEOLOGY Compass Bearings

Remember that a compass points to Magnetic North and not true north…the difference is called declination and is shown on the Topo map key, usually at the bottom, center

To measure a azimuth on a map, draw a line from the starting point to the destination and through any of the maps borders

Align the compass N-S or E-W with the map borderRead the bearing toward the destination

GEOLOGY Compass Bearings

Now imagine that you are in the wilderness with a compass and your Topo map

You know where you are and where you want to goLook at the Topo and find the azimuth to your

destinationSet the compass and see which way it pointsSimply follow the arrow to your destinationEstimate the distance you would need to walk from the

Topo (remember 1 square is 1 mile)

GEOLOGY Compass Bearings

Remember that a straight line is not always the fastest way to reach your destination

You may not be able to cross a lake or climb a mountain

This is the basic concept for the sport of Orienteering-finding markers and registers in an unknown area

GEOLOGY

ORIENTEERING uses a map and compass to find markers on an orienteering course. Rock Bridge has a course.

GEOLOGY

GEOCACHING is much like orienteering but uses a GPS system

GEOLOGY Some Cool Web sites-Let's Look Topozone.com Google Earth Earth.com

What is this?

Find St. Louis, Chicago, Los Angeles.

GEOLOGY Wrap-ups

1. What is a Topo Map? 2. What are contour lines? 3. What is the most commonly used contour

interval in Missouri? 4. What would X BM 1065 indicate? 5. How many acres are in a section?

GEOLOGY Wrap-ups

6. What are the advantages and disadvantages of GPS?

7. What is the UTM system? 8. What is the azimuth of Southwest? 9. What is declination? 10. What is Orienteering?