41
a simplification
iy a sufficient
5 the research
=ct with regard
implemented.
i, it is possible
structural, wall
¡orations etc...,
ted ones, of
¡rvation of the
jcture that, for
ts of the lines
the transverse
been set in the
>m each of the
ie have been
¡nt ones have
lination.
ie measuring
dence of the
ol that in this
neasurements
> the accuracy
nic theodolite
res enabling it
anithal angles
with accuracy of ± 1 cc , overlapped by diastimeter DISTO,
that is able to measure the distances with accuracy of ± 3
mm + 1 p.p.m.. The capacity of the instruments configured
in that way reaches 100 m considering characteristics of
the reflecting surface. As it is already well-known, a
diastimeter without reflectors performs the measuring over
the area determined by the intersection between emission
cone of the signal and the reflecting surface. That area,
then, increases in proportion to the distance and varies
from 6 mm to 60 mm for the distances between 10 and
100 m.
The correct collimation of the points is being marked by a
small laser tracer of Class 2 fixed on the side of DISTO.
A limited distance (approx. 15 m) between the vertices of
the measuring stations and the elements to be measured
has imposed a need to work with a very small zenithal
angle.
For the presumed values, moreover, the propagation of
the variance within measure of the azimuthal angles, has
failed to produce negative practical effects notwithstanding
very inclined visibility distances and the negative effect of
the residual error of vertical position.
The measurement of the profile, as it has already been
said, repeated independently from two nearby measuring
stations (half of a profile from each station) has enabled to
verify a result and exclude the arising of the systems.
With well-known expressions:
AO = k sen z+ D cos z
AX = - k cos z sen a + D sen z sen a
A V = -k cos z cos a + D sen z cos a
where a and z are the values of the measured azimuthal
and zenithal angle, D is an oblique distance measured
from diastimeter and k is a distance between collimation
axis of a theodolite and an axis of a diastimeter, the value
of the coordinates of the measuring points have been
determined reduced to a unique reference system.
In total, 1800 points (fig. 4) have been measured that,
thanks to a simple calculation program, have been
transformed into a DXF file, structured at different levels. In
that way, it was possible to visualize the results of the field
work through the graphic symbols of different colours, each
corresponding to the respective measuring station where
from the points have been acquired; that have made
immediately obvious the correspondence of the profiles.
Figure 5
Transverse section obteined with
topographic data.
Figure 6
The same section integrated with data
achieve from digital image rectification.
Figure 7
An example of image rectification aimed
to survey plain surfaces.