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1.2.2 Mixed quarry 
The mixed quarries are characterised both from open fronts 
and from the superficial and the deep stratum. For the first one 
we remand to the last paragraph, only adding that is difficult to 
determine the fronts of discontinuity nearly to the immersion 
under the water, hi this case due to the high influence of the 
relevant under water part, which is more regularly than the 
open parts, the decrease of the accuracy of the volume 
estimation with the decreasing of the density of points is lesser 
respect to the case of total open quarry. 
In this case the optimal grid is attested on a 20x20m grid. A 
grid of 5x5m describe sufficiently the volume of extraction. 
For the under water sectors we remand to the following 
paragraph. 
Fig. 7 The detail survey of a mixed quarry (Cemusco sul 
Naviglio). 
1.2.3 Under water quarry and sectors 
hi the case studio it has been surveyed 58933 points. 
For these cases is necessary to use a quality bathymeter: once 
guaranteed the accuracy on the measure of the deep , the 
problem is the georeferentiation of the data in the global datum 
of the quarry that is the national Gauss-Boaga datum RM40. 
Is fundamental to synchronise the bathymetric measure with 
the topographic measure of position. Particularly the 
bathymetric systems (in which is acquired in continuous the 
measure of the depth interpolating the position by the 
supposition of constant velocity of the ship along the course) 
are not reliable. The instrumentation considered optimal and 
then tested in the survey in the stratum is represented by an 
integrated system GPS-bathymeter that allows a regularly 
distribution of the points surveyed. In this case are used two 
antennas GPS, one positioned on 
a vertices of the fundamental network and the second on the 
ship. To survey the distance between the two antennas it isn’t 
requested the mutual visibility. Once defined the direction 
along which to trace the bathymetric sections, the system 
guides the course of the ship calculating in automatic the new 
courses in function of the density requested in the project of 
the survey. 
A PC allows to visualize in real time the points surveyed, the 
depth and the course traced shown by an arrow. 
The suggested characteristics of the instruments. The GPS 
modality adopted is the so called RTK (Real Time Kinematic), 
it has large diffusion, it is made by a Master station in 
correspondence of one vertices of the fundamental network and 
by a mobile antenna (Rover) positioned on the ship in 
correspondence of the bathymeter or in a position out of the 
centre but known. The only limits is the necessity of the 
mutual visibility of at least 5 satellites actually guaranteed 
during the day at our latitude. Tire two antennas are connected 
by a radio-modem and this allows to the rover receiver to 
calculate the position respect to the master and to the global 
datum in real time. Once predetermined the equidistant 
courses (5m for the interesting areas and 10 meters for 
remaining 
Fig. 8 The detail survey of an under water quarry (Peschiera 
Borromeo). 
areas) and introduced the data of the course in the navigation 
programme is obtained on video the directions which the ship 
has to follows in real time with GPS. Contemporary has been 
acquired the data position fixed in number of 2 per second and 
the data of the depth (obtained by the average of 5 observation 
of the echo sounder which measure every 2/10 of second. 
With this methodology it has been surveyed in the case studio: 
58933 points for the precedent case 
25396 points for the quarry totally under water. 
2. The DTM and the calculation of the volume 
The calculation of the volumes has been obtained building 
Digital Terrain Model (DTM) and interpolating the detail 
points surveyed for each quarry: 50.000 surveyed points tor the 
under water quarry and 15.000 points for the open quarry. The 
DTM can be obtained interpolating the height of the points to 
obtain a regular grid or a TIN network. The Software Surfer 
has been used to build the DTM (ver. 6.01 Golden Software) 
through Kriging standard interpolation. On the DTM are 
obtained the contour line (2m equidistant) to describe the 
orographic shape of the terrain.