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.