KRZYSZTOF PIETRUSZKA, ph.D.KRZYSZTOF PIETRUSZKA, ph.D.

e-mail :e-mail : pietrusz@uci.agh.edu.pl

www: www: http://galaxy.uci.agh.edu.pl

CC oo nn tt oo uu rr ssThe most common way of indicating relief on a map is using contours. A contour is a line connecting points of equal elevation. Contours are drawn by by interpolatinginterpolating between points whose positions and elevations have been measured and plotted.The vertical distance between level surfaces forming the contours is called the contour interval. The contour interval selection depends on the diversity of relief in the area being mapped as well as the purpose and scale of the map.

1. A contour is a line drawn on a plan joining all points of the same height

2. Contours cannot cross, split or join other contours,

3. The height between successive contours is called the vertical interval or the contour interval.

• Its value depends on the variation in height of the area being contoured.

• The contour interval is kept constant for a plan or map.

Contouring

113.0 112.8 112.6 112.4 112.2 112.0

Longitude

36.0

36.2

36.4

36.6

36.8

37.0

Lat

itu

de

Grand Canyon, U.S.A.

400

880

1360

1840

2320

2800

Ele

vati

on

900 3275 5650 8025 10400

Easting

8100

10400

12700

15000

17300

19600

21900

No

rth

ing

M t. S t. H elen s

5

10

15

A contoured spoil heap.

20

25

5

1015

20 25

contouring

from random spot heights

from a grid of spot heights

0.23208.00

LThis is a calculation method

208.23

207.45

X = ? Y = ?

0.780.55

X / L = 0.55 / 0.78 x = L * 0.55 / 0.78 = 0.71 = X

Y / L = 0.23 / 0.78 y = L * 0.23 / 0.78 = 0.29 = Y

208.23-207.45=0.78

208.00-207.45=0.45

208.23-208.00=0.23

To locate the position of the 8m contour between the two points

7.45 8.23

It is 0.55m above LH point

Draw a line 55 units long, below LH point

It is 0.23m below RH point

Draw a line 23 units long, above RH point

Join the ends of these two lines

The 8m contour point is at the intersection of the two lines

8m

This is a graphical method

Transparent paper

This is a graphical method

205.50

208.75

X

X

X

206.00

207.00

208.00

This is a graphical method

207.00

205.50

208.75296.00

298.00

208.50

298.00

Contour lines

205.25

297.00206.00

This is a graphical method

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.000.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

2 5

3 0

3 5

4 0

4 5

5 0

5 5

6 0

6 5

7 0

7 5

8 0

8 5

9 0

9 5

1500

1770

1850

2000

2150

2300

2450

2600

2750

2900

3050

F ron t R an ge , C o lorad o

Southwest Corner of the

Morrison Quadrangle, Colorado

nr E N elevnr E N elev

157 157 2210.00 2210.00 1021.00 -70.3 1021.00 -70.3 161 161 2166.48 947.21 -71.5 2166.48 947.21 -71.5 167 167 2108.90 990.92 -67.8 2108.90 990.92 -67.8

124 124 2119.40 1012.12 -101.2 2119.40 1012.12 -101.2 325 325 2594.37 1155.03 -94.5 2594.37 1155.03 -94.5 308 308 2864.83 1093.70 -80.8 2864.83 1093.70 -80.8 305 305 2905.61 1047.98 -88.3 2905.61 1047.98 -88.3 304 304 2899.95 1075.36 -85.0 2899.95 1075.36 -85.0 306 306 2882.82 1083.18 -76.8 2882.82 1083.18 -76.8 322 322 2762.22 1126.95 -100.7 2762.22 1126.95 -100.7 330 330 2710.86 1149.65 -96.6 2710.86 1149.65 -96.6 3252 2590.30 3252 2590.30 1134.53 -104.3 1134.53 -104.3 3251 2587.86 3251 2587.86 1118.09 -115.7 1118.09 -115.7 109 109 2574.61 1134.98 -102.6 2574.61 1134.98 -102.6 1233 2489.19 1233 2489.19 1108.38 -108.7 1108.38 -108.7 1231 2501.68 1231 2501.68 1126.47 -99.5 1126.47 -99.5 1331 2398.00 1331 2398.00 1025.00 -174.0 1025.00 -174.0 1311 2417.00 1311 2417.00 1064.00 -125.4 1064.00 -125.4 1391 2351.00 1391 2351.00 1082.00 -100.5 1082.00 -100.5 507 507 2704.24 2704.24 1257.35 -71.3 1257.35 -71.3 340 340 2641.79 2641.79 1174.38 -92.6 1174.38 -92.6 203 203 2616.16 2616.16 1260.10 -71.3 1260.10 -71.3 113 113 2558.44 2558.44 1158.38 -87.6 1158.38 -87.6

2200 2300 2400 2500 2600 2700 2800 2900

1000

1100

1200

Surface subsidence using GPS