Transcript Contouring - AGH University of Science and Technology

KRZYSZTOF PIETRUSZKA, ph.D.
e-mail : [email protected]
www:
http://galaxy.uci.agh.edu.pl
Contours
The 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 interpolating 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.
Contouring
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.
37
.0
36
.8
Grand Canyon, U.S.A.
2800
2320
Latitude
Elevation
.6
36
3
6. 4
1840
1360
880
400
3
6. 2
.0
36113.0
112.8
112.6
112.4
Longitude
112.2
112.0
21900
19600
Northing
17300
15000
12700
10400
8100
900
3275
5650
8025
10400
Easting
Mt. St. Helens
A contoured spoil heap.
5
10
15
25
20
15
10
5
20
25
contouring
from random spot heights
from a grid of spot heights
This is a calculation method
208.23-208.00=0.23
L
208.23
208.00-207.45=0.45
0.23
208.00
0.78
0.55
207.45
X=?
Y=?
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
To locate the position of the 8m contour between the two points
7.45
It is 0.55m above LH point
8m
8.23
This is a graphical method
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
This is a graphical method
Transparent paper
This is a graphical method
208.75
208.00
X
207.00
X
206.00
X
205.50
This is a graphical method
207.00
208.75
298.00
296.00
Contour lines
205.50
208.50
205.25
297.00
206.00
298.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
3050
2900
2750
2600
2450
2300
2150
2000
1850
1770
1500
Front Range, Colorado
Southwest Corner of the
Morrison Quadrangle, Colorado
nr
157
161
167
124
325
308
305
304
306
322
330
3252
3251
109
1233
1231
1331
1311
1391
507
340
203
113
E
2210.00
2166.48
2108.90
2119.40
2594.37
2864.83
2905.61
2899.95
2882.82
2762.22
2710.86
2590.30
2587.86
2574.61
2489.19
2501.68
2398.00
2417.00
2351.00
2704.24
2641.79
2616.16
2558.44
N
1021.00
947.21
990.92
1012.12
1155.03
1093.70
1047.98
1075.36
1083.18
1126.95
1149.65
1134.53
1118.09
1134.98
1108.38
1126.47
1025.00
1064.00
1082.00
1257.35
1174.38
1260.10
1158.38
elev
-70.3
-71.5
-67.8
-101.2
-94.5
-80.8
-88.3
-85.0
-76.8
-100.7
-96.6
-104.3
-115.7
-102.6
-108.7
-99.5
-174.0
-125.4
-100.5
-71.3
-92.6
-71.3
-87.6
1200
1100
1000
2200
2300
2400
2500
2600
2700
2800
2900
Surface subsidence using GPS