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Figure 4. Equalized histogram of M4.DAT image.
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Figure 5. Display of M4.DAT equalized image.
GIS Lab # 8. PERSPECTIVE DRAWING
Write a computer program and make a perspective
presentation of the given digital terrain data
which are in a matrix form 21-rows by 27 columns
and reside in the file LAB8.DAT. Those data have
been obtained from a solid waste disposal site in
the area of Lemonou. The perspective form will be
obtained by assuming that a camera with focal
length equal to one is taking a picture of the ter-
rain.
Given data will be (see also Fig. 1): (a) The digi-
tal terrain data in a matrix form (b) The XL, YL,
ZL coordinates of the camera station (c) The angle
s of the camera axis and a horizontal plane (d) The
azimuth Az of the principal plane. The photo-coor-
dinates x, y of all grid nodes will be calculated
from the following projective equations.
DX = X-XL, DY = Y-YL, DZ = Z-ZL
DX.cos(Az) - DY.sin(Az)
DX.sin(Az)cos(s) * DY.cos(Az)cos(s) - DZ.sin(s)
DX.sin(Az)sin(s) * DY.cos(Az)sin(s) * DZ.cos(s)
DX.sin(Az)cos(s) + DY.cos(Az)cos(s) - DZ.sin(s)
135
Figure 6. Stretched histogram of M4.DAT image.
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Figure 7. Display of M4.DAT stretched image.
Note that the equations above are derived from the
tilt, swing, Azimuth collinearity equations of
photogrammetry (swing = 180, s = 90 - tilt) as
shown in Fig. 8.
(Xi M1) Camera. Station
Figure 8. Perspective view parameters.
