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alignment af the laser beams has been obtained with an error of
about 0.1 mrad, corresponding to 0.3 m for a distance of 2 km.
The second problem regards the collimation device. For the first
measurements, a manually driven mirror, having a diameter of
0.4 m, has been used. Due to the telescope configuration
(Cassegrain type), and the presence of the detector in the focus,
it is difficultous to control the collimation line. Two graduated
circles allow to roughly read azimuth and vertical angles of the
beams.
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Figure 8: Coelostat
The results of a set of angular measurements, obtained using the
HeNe laser beam, showed standard deviations equal to about
one sexagesimal degree.
To obtain a better accuracy, and to drive remotely the laser
beams, a coelostat has been deigned and realized (See Figure 8).
It will be mounted on the existing iron framework on the roof of
the laboratory.
Two motors allow the rotation of the whole coelostat around the
vertical telescope axis, and of the second mirror around a
horizontal axis. The movements are geared down, to have a fine
collimation, and the motors are computer driven.
DEVELOPMENTS
In the next months, some measurements are foreseen, using
vapour targets (exhaust on the chimney of a thermal power
plan).
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998
A set of measurements is also foreseen, to check the angular
accuracy of the coelostat.
A mobile system has been designed and will be realized,
allowing a mapping of large zones and measurements in peculiar
sites (thermoelectrical power plants, factories, etc..).
A positioning system, using GPS and an inertial system, will be
set up. The results of the measurements will be used to set up a
GIS for the atmospheric parameters.
CONCLUSIONS
To check the geometric accuracy of the DIAL station at the
University of Calabria, both range and angular measurements
have been realized, and the results have been compared with
total station measurements. The geometric accuracy of the DIAL
system is generally sufficient for the range measurements,
whilest the angular accuracy can be improved. A new coelostat
has been built and will be mounted, to ensure a better angular
accuracy.
REFERENCES
Barbini R., Colao F., Fantoni R., Palucci A., Habel R., Cappai
M., A.Sollai, Bellecci C., Artese G., De Donato F., Frangella G.,
Zupo M.S., Giardini Guidoni A., Morone A., Snels M., 1991.
Una iniziativa integrata di telerilevamento laser in Italia. II
' Nuovo Saggiatore, 7 (4), pp. 30 - 37
Bellecci C., Artese G., De Donato F., Zupo M.S., 1991. Tecnica
DIAL per il telerilevamento di parametri atmosferici di interesse
ambientale. Proceedings of the IV National Congress of the
Italian Society of Echology, Cosenza, Italy.
Bellecci C., De Donato F., Gaudio P., Valentini M.,1993. The
CO2 LIDAR/DIAL facility at the University of Calabria for
atmospheric pollution remote sensing. Proceedings 1st National
Symposium on Environmental Physics, Brescia, Italy.
Measures R.M., 1984. Laser Remote Sensing. John Wiley and
Sons, New York.
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