Geodesy deals with the precise size, shape and gravitational field of the earth. The actual physical
surface of the earth is very irregular. A more uniform surface is the geoid which is the equipotential
surface which coincides with mean sea level (MSL). This too is irregular in shape in the sense that it
cannot be represented by a finite mathematical formula, due to variations of gravity. In dealing with
precise dimensions and the shape of the earth it is necessary to adopt a reference surface on which
mathematical computations can be carried out and variations of the geoid from this reference surface
could be indicated by elevations and depressions, termed Geoidal undulations above and below the
reference surface.
The mathematical surface which best fits the geoid is an ellipsoid of rotation.
The dimensions of the ellipsoid vary according to the one selected by each country and for Sri Lanka
the dimensions of the semi-major and minor axes are 6377276.345 meters and 6356075.413 meters
respectively which is the Everest 1830 of the Earth used in the Survey of India. Observations of angles and distances for surveying are carried out on the earth's physical surface. They
have first to be reduced to the ellipsoid before computations commence. Computations are done
using the dimensions of the ellipsoid adopted and appropriate formula. The first control
network or principal triangulation of Sri Lanka was carried on Everest 1830. The principal triangulation of Ceylon began in 1857 with the measurement of the Negombo
(Kandawala to Halgastota) baseline. The triangulation observations were made on pillars at
Kandawala and Halgastota (See photographs below, at present known as Landesi Kuluna)
with 8-inch and 13-inch vernier theodolites, and were completed in 1885. This triangulation
was subsequently connected to the Indian Triangulation in 1887 by a long, narrow triangulation
chain running roughly through Batticaloa, Trincomalee, Manar and Delft. The Ceylon network was
recomputed with some additional observations in 1890 due to inconsistencies occurring mainly
in the minor triangulation station.
M.Sc. in GIS and Remote Sensing(Uoj, SL)
Higher Diploma in Surveying (ISM, Diyatalawa, SL)
B.Sc.in Physical Science (UoJ, SL)
M.Sc. in GIS and Remote Sensing(UoP, SL)
Higher Diploma in Surveying (ISM, Diyatalawa, SL)
B.Sc.in Surveying Sciences (ISM, Diyatalawa, SL)
Diploma in Computer Science (NIBM)
Advanced Diploma in Surveying (ISM, Diyatalawa, SL)
B.Sc. in Surveying Sciences (ISM, Diyatalawa, SL)
B.Sc. in Surveying Sciences (ISM, Diyatalawa, SL)
B.Sc. in Surveying Sciences (UoS, SL)
B.Sc. in Surveying Sciences (UoS, SL)
B.Sc. (Hons) in Surveying Sciences (ISM, Diyatalawa, SL)
B.Sc. (Hons) in Physical Science (UoR, SL)
a). Establish control points using GNSS.
b). Maintain control points and geodetic network of triangulation.
c). Primary, Secondary and teritary Levelling.
d). Maintain Level network and fundamental Bench marks.
e). RTK survey for sporadic work and construction works.
f). Issue Geodetic coordinates of control GNSS points.
g). Issue MSL heights.
h). Check and approve GNSS coordinates which are submitted by private organizations.
i). Calibration of EDM instruments.
Link to Control Point Data Portal
