Title: Topographic Maps
1Topographic Maps
- Dual Credit Geology
- Lab 8
2Topographic 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
3Relief Map
4Topographic Map Features
- Title and Legend
- Scale
- Scale Conversion
- Latitude and Longitude
- Township, Range, and Section
- True North and Magnetic North
5Title 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)
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7Scale
- The relationship between true ground distance and
distance on the map - Three types used on Topographic maps
- Verbal scale
- Graphic scale
- Fractional scale
8Verbal 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
9Graphic 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
10Graphic Scale
11Fractional 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
12Example 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).
13Graphic Fractional
14Scale Conversion
- Converting from one scale to another
- Convert from fractional to verbal simply divide
by the conversion factors as shown
15Conversion
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
16Conversion
- 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
17Conversions
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
18Latitude 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)
19USGS 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
20TopographIc
21Township, 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)
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23Ranges
- 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
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25Townships
- 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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27Sections
- 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)
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29True 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
30Assignment