Daryl V. Pascua
December 02, 2008
BSAEn4
AENGR 425 – AQUACULTURE ENGINEERING
Laboratory Exercise No. 1
Contour Mapping
I. INTRODUCTION
A contour map is a map illustrated with contour lines, for example a topographic
map, which thus shows valleys and hills, and the steepness of slopes. The
contour interval of a contour map is the difference in elevation between
successive contour lines.
More generally, a contour line for a function of two variables is a curve
connecting points where the function has a same particular value. The gradient of
the function is always perpendicular to the contour lines. When the lines are close
together the length of the gradient is large: the variation is steep. If adjacent
contour lines are of the same line width, the direction of the gradient cannot be
determined from the contour lines alone. However if contour lines rotate through
three or more widths, or if the lines are numerically labeled, then the direction of
the gradient can also be determined from the contour lines.
Contour lines are curved or straight lines on a map describing the intersection of
a real or hypothetical surface with one or more horizontal planes. The
configuration of these contours allows map-readers to infer relative gradient of a
parameter and estimate that parameter at specific places. Contour lines may be
either traced on a visible three-dimensional model of the surface, as when a
photogrammetric viewing a stereo-model plots elevation contours, or interpolated
from estimated surface elevations, as when a computer program threads
contours through a network of observation points of area cancroids. In the latter
case, the method of interpolation affects the reliability of individual isolines and
their portrayal of slope, pits and peaks (see Davis, 1986, Statistics and data
analysis in geology).
A contour line (also level set, isopleth, isoline, isogram or isarithm) of a
function of two variables is a curve along which the function has a constant
value. In cartography, a contour line (often just called a "contour") joins points of
equal elevation (height) above a given level, such as mean sea level.
II. PROCEDURE
1. An isohyetal line with 0.2 m interval was made.
2. A line for the possible location of drainage canal was drawn.
1
III.
Station
RESULT AND DISCUSSION
X
Y
Elevation (m)
Station
X
Y
Elevation (m)
1
120
16
140.2
19
120
15.4
136
2
120.2
16
141
20
120.2
15.4
132.2
3
120.4
16
138.7
21
120.4
15.4
134.8
4
120.6
16
139.6
22
120.6
15.4
134.6
5
120.8
16
139.8
23
120.8
15.4
134.8
6
121
15.8
139.7
24
121
15.2
135
7
120
15.8
136.8
25
120
15.2
139
8
120.2
15.8
140.2
26
120.2
15.2
136
9
120.4
15.8
139.2
27
120.4
15.2
130.6
10
120.6
15.8
138.7
28
120.6
15.2
130.7
11
120.8
15.8
138.6
29
120.8
15.2
133
12
121
15.8
138.8
30
121
15.2
132.6
13
120
15.6
134.8
31
120
15
136.2
14
120.2
15.6
136.6
32
120.2
15
130.6
15
120.4
15.6
136.8
33
120.4
15
130.1
16
120.6
15.6
136.7
34
120.6
15
130
17
120.8
15.6
137
35
120.8
15
130.7
18
121
15.6
137.3
36
121
15
130.8
16.00
15.90
Possible
Drainage canal
15.80
15.70
15.60
15.50
15.40
15.30
15.20
15.10
15.00
120.00
120.10
120.20
120.30
120.40
120.50
120.60
120.70
120.80
120.90
121.00
2
Using the given data of a contour map, it was plotted as shown in page 2. It
was done in the computer using the software of a contour mapping. In addition,
it was tried to plot in a grapping paper by manual although it is difficult and time
consuming.
Comparing the two methods of mapping between manual and the use of
computer, the use of computer is highly appreciated because of its accuracy.
Also, it is easier and faster than the manual method.
The possible location of a drainage canal was determined and a line as shown
in the map presented it. The selection of the drainage canal was based on the
elevation. You can recognize the elevation if you know how to read this kind of
map.
IV. CONCLUSION
The two methods of contour mapping were learned and practiced by us. We
gained experience on how to plot a certain map given the longitude and latitude,
and elevation of each stations.
Furthermore, the knowledge and skill we got from this activity might be used
in designing fishponds, cages and other aquaculture structures.
V. REFERENCE
a) http://en.wikipedia.org/wiki/Contour_line
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