steep slope (Verano Brianza). 
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. In 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 (Cernusco sul 
Naviglio). 
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. The 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 
1.2.3 Under water quarry and sectors 
In 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 
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 for 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