REPORTER 39

olombia
From the ground to the map and then to the land register plan with the
Leica INFOCAM system.
cal restitution systems,
digitising stations and
precision plotters. Previously
on maps, despite great
production expense, it was
often the case that hardly a
course of a river could be
recognised, if it existed at
all, today, detailed contours
and current changes
brought about by building
work can be recorded and
displayed in only a fraction
of the time once needed.
Printing plates in various
scales for the same territory
no longer have to be individually
engraved by hand
but can be produced from
one and the same database.
This combines various
types of information and
contains, for example, not
only the boundaries of parcels
of land but also their
current use, owner etc.
Once the required data is
stored in the database, any
random section of the land
register map can be printed
within two minutes (see picture).
The National Survey
In order to provide maps
with coordinates (geographic
referencing), the
area to be represented must
already contain some
points with known
coordinates which have
already been surveyed. In
the case of national maps,
the National Survey is
responsible for covering the
country with a network of
surveyed points (the
national grid).
In Colombia the IGAC had,
during the Forties in
co-operation with the
former US Defense
Mapping Agency (DMA,
now the National Imagery
and Mapping Agency
NIMA) had already
established such a nationwide
network. It consists
mainly of polygons which
connect astronomically
determined points. Because
of the height of the
Cordilleras, the impenetrability
of the Amazon basin
and the size of Colombia
(about thirty times that of
Switzerland) the work
turned out to be extraordinarily
laborious and
only a heavily built-up part
of the country could be
surveyed. Because the
methods used at that time
(angle measurement with
optical theodolites)
necessitated visual contact
between the points, these
were located mostly on
mountain summits where
access was difficult, thus
Colombian-Swiss co-operation
on the new national survey of
Colombia with Leica GPS.
(Photos: D. Egger)
increasing the cost of
surveying them and
reducing their usefulness.
In the meantime, mankind,
wind and weather have
destroyed more than 50%
of these points of the
national grid. Additionally,
in the course of modernisation,
serious distortions and
irregularities have come to
light. Thus, the existing
National Survey no longer
suffices for the increased
demands made by modern
cartography. In 1994 as a
logical consequence, the
Geodesia section of the
IGAC began the ambitious
project of a new national
survey for Colombia – with
more easily accessible
points, more exact
coordinates and reduced
costs.
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