131 
OPERATOR 
Translation 
Scaling/rotation 
Intersection 
Number of points 
Point of closest proximity 
Overlaps? 
Overlaps to left? 
Overlaps to right? 
Distance between 
Left of? 
Is below? 
Is right of? 
Is above? 
Intersect or overlaps 
Is horizontal? 
Is perpendicular? 
Length or circumference 
Is vertical? 
Is parallel? 
Contained or on 
Center of 
Same as 
Table 13 - The POSTGRES geometric operators 
REFERENCES 
AA.VV., 1994, International School for determination and 
use of the geoid - Lecture Notes International Geoid 
Service - DIIAR - Politecnico di Milano. 
Barzaghi R, Brovelli M. A., Manzino A., Sguerso D, Sona 
G., 1996, The new Italian quasi-geoid: ltalgeo95, 
Bollettino di Geofisica e Scienze Affini, anno LV, 1: 57-72. 
Biagi L., Brovelli M.A. , Salemi G., 1998, Tecniche GIS 
per la gestione e rappresentazione dei geoidi, Atti della II 
conferenze nazionale ASITA, Novembre 1998, pp. 317- 
322. 
Biagi L., Brovelli M. A. and Salemi G., 1999, Geodetic 
Data Management with GIS and DBMS Techniques, 
I.Ge.S. Bulletin n. 8. 
Burroghs P. A. , 1986, Principles of Geographic 
Information Systems for land resources assesment, 
Oxford University Monographs on Soil and Resources 
Survey, n. 12, Oxford, Uk:Clarendon Press. 
Clamons S. F: and Byars B. W: , 1997, GRASS 4.2 
Programmer’s Manual, Baylor University GRASS 
Research Group. 
Codd E., 1970, A relational Model of Data for Large 
Shared Databases, CACM, June 1970. 
Healy R.G., 1991, Database Management System in 
Geographical Information Systems (M.F.Goodchild, D. 
Maguire, D. Rhind eds.) , Longman Scientific & Technical, 
voi. 2, pp. 251-267; 
FUNCTION 
DESCRIPTION 
box(point,point) 
Convert point to box 
Area(box) 
Area of box 
Isopen(path) 
TRUE if this is an 
open path 
Isclose(path) 
TRUE if this is a 
closed path 
Circle(point,float8) 
Convert to circle 
Polygon 
(npts, circle) 
Convert to polygon 
with Npts points 
center(circle) 
Center of object 
radius(circle) 
Radius of circle 
area(circle) 
Area of the circle 
Diameter(circle) 
Diameter of the circle 
Table 14 - The POSTGRES geometric functions 
Jones C., 1997, Geographical Information System and 
Computer Cartography, Addison Wesley Longman 
Limited, Essex, England. 
Laurini R. and Thomson D. , 1992, Fundamental of 
Spatial Information Systems, The Apic Series,San Diego, 
Ca. 
Pennywitt K.E., Barrett P.J., Ray M.M., 1992, GRASS-to- 
DBMS interfacing : a survey of current research effort with 
recommendations for future GRASS enhancements, 
Report of the Project no. A-9110-000, Computer Science 
and Information Technology Laboratory Georgia Tech 
Research Institute. 
Stonebraker M .R. and Rowe L. A., 1986, the Design of 
POSTGRES, Proc.ACM-AM-SIGMOD Conf. On 
Management of Data Int. Conf.on the Mgt. Of Data. 
Stonebraker M. Anton J. And Hanson E., 1987, 
Extending a Database System with procedures, ACM 
TODS, September,!987. 
USACERL, 1993, GRASS 4.1 User’s Reference Manual, 
Champaign, Illinois, United States Army Corps of 
Engineers Construction Engineering Research 
Laboratories. 
Yu A. and Chen J„ 1995, The POSTGRES95 User 
Manual, Regent of the University of California.