Figure 6: Perspective view of the DTM. The ortho-image is overlayed in this projection.
With the GPS profile addressed above the opportu-
nity is given for the first rigorous evaluation of the
MOMS potential for DTM generation. Therefore, the
present investigation focuses on this profile. In fig-
ure 7 the height profile is plotted as a function of the
profile length. Even though precisely the ellipsoidal
height difference with respect to a reference point is
shown, we just want to refer to this height difference
as the profile height.
35
œ
©
UA. A Rp ;
Yo po i dapes
7 Y |
= M
5 |
0 2500 5000 7500
N
Cc
-—
a
GPS height [m]
N
©
|
NY
GES
©
| |
10000 12500 15000
profile [m]
Figure 7: GPS profile.with 3228 DTM check points
The first look at the data shows an extremely flat ter-
rain of less than 25 m height difference on a length
of more than 16 km. The profile is resolved with a
5 m spacing interval which delivers 3228 DTM check
points. To get an impression on the undulation of the
terrain the first derivatives are calculated (figure 8).
Apart from one point (at profile length 2000 m) the
height gradients are below 0.5 m, i.e. the slope is
even locally less than 10 %.
0.5
Me
GPS gradients in height [m]
©
4
=
-1
0 2500 5000 7500 10000 12500 15000
profile [m]
Figure 8: Gradients of height profile
The DTM evaluation profile was recorded with a rov-
ing GPS antenna. The 3-D profile data have been
collected in a kinematic mode of GPS surveying. For
that purpose the antenna was mounted on a Land-
cruiser and the vehicle was slowly driven parallel to
the fence along the track. Projection of the 3-D pro-
file into all three channels using the given orientation
shows nearly perfect straight lines. For a closer look
at each of these lines, straight lines are fitted to the
data. The deviations of the projected image lines
from the straight lines are plotted in figure 9 for all
three channels.
-2.5
0 200 400 600 800 1000 1200
row [pixel]
Figure 9: Deviation of the projected 3-D profile from
straight lines.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
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