Sistema Vertical Clasico Y Moderno

The existing vertical system in Colombia was established with reference to the
Mean Sea Level (MSL) at the tide gauge in Buenaventura on the Pacific Ocean
observed from 1951 to 1968. The firstorder leveling network has an extension of
approximately 26 000 km covering 55% of the country (Figure 1). Although gravity
surveys have been performed, the observed heights have not been corrected forthe
gravity effects. Their relation to the geoid/quasigeoid is thus not realized.
The system presents large inconsistencies due to crustal movements. In some releveled
lines differences from -0,266m to 0,296 m have been found over an interval
of 44 years. Furthermore, it is not compatible with the height systems of
neighboring countries. Recently, the leveling networks of Colombia, Venezuelaand
Ecuador were connected by spirit leveling and by GPS. The connection between the
Ecuadorian and the Colombian height systems (in Ipiales) shows a difference of
0,075 m, while between Venezuelaand Colombia the discrepancies in two different
zones (Maicao and Cucuta, Figure 3) are -0,32 m and +0,32 m, respectively.
The classical height system
The modern height system
The definition ofthe new vertical system for Colombia is developed according to
the recommendations of SIRGAS Working Group III "Vertical Datum":
Type of heights: It includes ellipsoidal and normal heights. Thenormal ones will be used
mainly for practical surveying in applied geodetic developments, while the others will serve
as "reference heights" to satisfy scientific purposes and global networkrequirements.
Vertical Reference Surface: The quasigeoid (GEOCOL2001, Figure 2) was
calculated by Molodensky's method using the EGM96 geopotential model combined
with Faye anomalies and satellite altimetrydata.
Vertical Reference Frame: The stations of the reference network (Figure 3) refer to the
national geocentric reference frame (MAGNA within SIRGAS), they are connected by
spirit leveling, and...