Topographic Maps - PowerPoint PPT Presentation

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Topographic Maps

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Topographic Maps Dual Credit Geology Lab # 8 – PowerPoint PPT presentation

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Title: Topographic Maps


1
Topographic Maps
  • Dual Credit Geology
  • Lab 8

2
Topographic Maps
  • Maps in which the three-dimensional configuration
    of the Earths surface (hills and valleys) are
    represented on a flat, two-dimensional map
  • Relief the difference in elevation between the
    high and low points of an area

3
Relief Map
4
Topographic Map Features
  • Title and Legend
  • Scale
  • Scale Conversion
  • Latitude and Longitude
  • Township, Range, and Section
  • True North and Magnetic North

5
Title and Legend
  • Title (of map) usually named after a major
    geographic feature in the map area
  • Legend key to explain symbols used on map
  • (All USGS maps use the same legend)

6
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7
Scale
  • The relationship between true ground distance and
    distance on the map
  • Three types used on Topographic maps
  • Verbal scale
  • Graphic scale
  • Fractional scale

8
Verbal Scale
  • Gives the scale in words
  • Example 1 centimeter 4 kilometers
  • Meaning one centimeter on the map 4 kilometers
    on the ground
  • You will NOT find verbal scales on a Topo map
    but must be able to calculate the verbal from the
    fractional scale

9
Graphic Scale
  • Graphic (or bar) scale shown as a line or bar
    that has been divided into units representing
    distances on the ground
  • Distance easily measured with a ruler
  • Always found on Topo maps - usually along the
    lower margin

10
Graphic Scale
11
Fractional Scale
  • Ratio between one unit distance on the map and
    the corresponding distance on the ground
  • 150,000 means one unit on the map corresponds
    with 50,000 OF THE SAME unit on the ground
  • Any units may be used -
  • BUT the units must be the same

12
Example of Fractional Scale
  • 124,000
  • Means - one inch on the map represents 24,000
    inches on the ground.
  • (Or one centimeter on the map represents 24,000
    centimeters on the ground - or any other unit you
    want to choose).

13
Graphic Fractional
14
Scale Conversion
  • Converting from one scale to another
  • Convert from fractional to verbal simply divide
    by the conversion factors as shown

15
Conversion
Fractional scale Metric System English System
1400,000 1 cm 400,000 cm 1 in 400,000 in
1 cm 400,000 cm x 1 km/100,000 cm 1 in 400,000 in x 1 ft/12 in
1 cm 4 km 1 in 33,333 ft x 1 mile/5,280 ft 1 in 6.3 mile
16
Conversion
  • To convert from verbal to fractional do just the
    opposite and multiply by the conversion factors
  • Since the fractional scale is a ratio, you
    multiply by the conversion factors until you have
    the same units on both sides of the equal sign

17
Conversions
Verbal Scale Fractional Scale
1 inch 2 miles 1 in 2 mi x 5,280 ft/mi
1 in 10,560 ft x 12 in/ft
1126,720
1 centimeter 4 kilometers 1 cm 4km x 100,000 cm/km
1 cm 400,000 cm
1400,000
18
Latitude and Longitude
  • Latitude lines run parallel to equator, east
    and west measured either north or south of 00
    (equator)
  • Longitude lines run vertically, north and
    south measured either east or west of 00
    longitude (Prime Meridian)

19
USGS Topographic Maps
  • Quadrangles bounded on north and south by lines
    of latitude on east and west by lines of
    longitude
  • Common size map is a 15 minute quadrangle (15 of
    longitude x 15 of latitude)- fractional scale
    162,500

20
TopographIc
21
Township, Range, and Section
  • Township/range system - designate small areas of
    land very accurately
  • Use one or more east-west lines called base
    lines, and one or more north-south lines called
    principle meridians
  • From baseline and meridians are additional E/W
    and N/S lines measured along a 6 mile spacing
    creating a grid pattern 6 miles x 6 miles (36 sq
    miles)

22
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23
Ranges
  • Squares along the N/S columns are called ranges
  • Numbered either East or West of principle
    meridian
  • On east of principle meridian R1E, R2E, R3E,
    R4E, to west of meridian R1W etc.
  • As you go farther east and/or west numbers will
    increase

24
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25
Townships
  • Squares along the E/W strips are called townships
  • Numbered from baseline in similar manner to
    ranges
  • (T45N, T56S and so on)
  • As you go farther east and/or west numbers will
    increase

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27
Sections
  • Since squares are 6 miles each they can be
    further divided into 36 one-mile square sections
  • Sections numbered 1 to 36 beginning with 1 in
    upper northeast corner, ending with 36 in
    southeast corner
  • Every section can be subdivided into quarter
    sections, designated NE, NW, SE, and SW (These
    can also be subdivided even further)

28
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29
True North and Magnetic North
  • All maps need an arrow so users can determine
    the orientation of geographic north (900 N
    latitude)
  • North usually at top of map (east to right, west
    to left, and south to the bottom)
  • Magnetic north is offset from the geographic
    (true) north
  • The angle between true and magnetic north is
    called the magnetic declination and varies
    depending on location of the map

30
Assignment
  • Lab 8 Topography
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