Establishment of a Unified Country-Wide Plane Coordinate System For Zambia
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Date
2016
Authors
Mulenga, Prosper S
Journal Title
Journal ISSN
Volume Title
Publisher
University of Zambia
Abstract
Planet Earth is approximately spherical in shape, and is three dimensional. To map the Earth on
a flat piece of paper, in two dimensions, a map projection must be carried out. A map
projection is a mathematical technique of how to represent the Earth’s curved surface on a flat
surface. In Zambia, the map projection used for national mapping is the Universal Transverse
Mercator (UTM) in 6 degree zones. Globally UTM zones run from zone 1 to zone 60 with
Zambia falling onto zones 34, 35 and 36, and with central meridians at 21⁰ E, 27⁰ E and 33⁰ E,
respectively. The central meridians and the equator form three separate plane coordinate
systems, with origins at the intersection of the equator and the particular central meridian.
Map projections come with distortions since there is “stretching” or “shrinking” of the curved
surface of the reference ellipsoid or spheroid. In order to compute distortions, a scale factor is
introduced to determine scale errors from the central meridian. For UTM projection the scale
factor at the central meridian is 0.9996. To avoid negative coordinates for the southern
hemisphere and the western part of the central meridian, a false easting and northing of
500,000m and 10,000,000m are introduced, respectively.
The problem with the UTM projection system is that data from different zones cannot easily be
combined to create integrated, seamless maps of geographic features across zone boundaries.
Therefore, in this study, the UTM projection and grid system was modified to cover the whole
country Zambia in a single zone. To achieve this, a computer program was written to determine
the scale factor at central meridian suitable for country-wide mapping. The central meridian
was set to 28⁰ E, and the scale factor at the central meridian was reduced to 0.9984 to minimise
the mean scale error of mapping. A False-Easting of 800,000m was applied to eliminate
negative coordinates, while a False-Northing of 10,000,000m was maintained.
The new plane coordinate system is intended to be used for country-wide, seamless
landcover/use mapping projects such as Task 151 of the Southern African Science Service
Centre for Climate Change and Adaptive Land Management (SASSCAL) project.
Description
A thesis in Engineering
Keywords
Grids (Cartography)--Zambia , Universal transverse Mercator projection (Cartography) , Map projection. , Map projection--Data processing.