Särtryck ur Svensk Lantmäteritidskrift nr 3 1964
519
Photogrammetry in the Tropics
By Dr. Percy Tham, Stockholm*)
Abstract
In tropical Africa, the photogrammetrist will meet with particu
lar difficulties in the performance of aerial photography. The quite
special meteorological conditions as the desert »harmattan» wind will
cause problems when a first-rate photograph is required. Rather often,
the infrared film is the only way to master these meteorological obstac
les.
The photographic definition will be decisive of the recognition of
typical landmarks required as control points for the photogrammetric
mapping. Within the African rainy forest-region along the equator
the villages as well as the single huts in the dense bush are normally
the most identifiable landmarks with the huts glaringly contrasting to
the sandy ground.
But a hunter’s hut, for instance, often being the only available land
mark in the bush will be overgrown and get rotten in a couple of years
if not frequently used.
On the other hand, very old villages considered to be derived from a
period of some 200 years have been discovered by stereoscopical
interpretation.
As a summing up, it may be emphasized that, on the one hand,
villages are obliterated in a period of only 4—5 years leaving no trace,
while, on the other hand, old villages of some 200 years are brought
into relief in the stereoscopical image.
This fact I would like to characterize in some measure as a paradox.
1. Introduction
In the Tropics, the leader of a photographic expedition has to face
conditions that make special measures necessary. The aircraft has to
work in an exceptional heat and humidity, the laboratory will meet
with particular difficulties to temper the developing and fixing baths,
and the camera-man will get troubles when trying to master the compli
cated atmospheric conditions.
*) Mapping Consultants Ltd (AB Ivartkonsult), Stockholm.
This paper has been published by courtesy of LAMCO Joint Venture.