GEOLOGY CMU Bill Palmer Lecture 11 Topo Maps

GEOLOGY  Topo Maps  A two-dimensional representation of a three- dimensional land surface  Use Contour lines to show relief  Useful to geologist and hunters, hikers, campers, developers, etc.  Also known as Quadrangle maps as they have four sides

GEOLOGY  Topo Maps  North is at top  Look at key to tell difference between true north and magnetic north.  Declination is degrees between N and Magnetic N  Symbols-look at handout for standard symbols  Green=Forest  Purple=photo revision

GEOLOGY  Topo Maps  Contour lines-brown squiggly lines that connect points of equal elevation  Usually 20 intervals in MO  Dark 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 Maps  Contour lines rarely ever cross-Overhanging cliff or rock bridge  The closer contour lines, the steeper the landscape  The farther apart contour lines, the flatter the landscape  “Vs” in contour lines point uphill  You 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 fieldsCheck scale on bottom of map

GEOLOGY  Topo Maps  Public Land Survey  Began in 1700s  Divided country into a grid of 6x6 miles  Most states follow-in SW Spanish land grants usurp  N-S are Townships  E-W are Range  So any square can be described by its T and R  T4S 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 acres  A square ¼ mi X ¼ mi is 40 acres.

GEOLOGY  GPS  GPS is Global Positioning Satellites  28 satellites are 12,000 miles above earth  They send a signal to a GPS receiver  Originally used by military for bombing, missiles, etc.  Now can be used by public free  Public systems are less accurate than military  Military systems =millimeters; public systems = feet  GPS 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

 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:  E and N  This would be meters East of the west edge of zone 18 and meters north of the equator

UTM ZONES

UTM GRIDS

GEOLOGY  UTM  Info on Topo map margins gives the UTM  Therefore,a hiker can use both a GPS and a Topo map when hiking  Some GPS units can incorporate a Topo map so a hiker can see exactly where they are  All 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 bearing  North=0 degrees  East=90 degrees  South=180 degrees  West=270 degrees  A circle has 360 degrees  Azimuths 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 border  Read 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 go  Look at the Topo and find the azimuth to your destination  Set the compass and see which way it points  Simply follow the arrow to your destination  Estimate 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?