47 
Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
Airphoto map control with Landsat - An alternative 
to the slotted templet method 
W.D.Langeraar 
Euroconsult. Arnhem, Netherlands 
ABSTRACT: Negative results experienced with the slotted templet method using aerial photographs that are 
tilted and have varying scales, have prompted the development of a more suitable method to produce basemaps 
under field conditions. Using Landsat as cartographic control it has become possible to assemble airphotos 
into geographic basemaps with a mean accuracy of 1.5 mm on a photo scale of 1/20.000. This has been 
empirically determined in south-eastern Irian Jaya using tilted airphotos with varying scales. Comparable 
accuracy could have been obtained had slotted templets been assembled to a control density of one control 
point per 85 accurately flown airphotos. Advantages of this approach over the slotted templet method are: 
* Photo tilt and scale variations do not disturb map accuracy. 
* Field data collected along survey lines can always be located on airphotos and thus integrated in the 
interpretation. 
* No ground control required prior to flying. 
- Landsat control is always evenly distributed, and so 
* Map compilation is much less time consuming. 
In remote areas, the airphoto map control method using 
for the production of an adequately accurate basemap to 
1 INTRODUCTION 
1.1 Purpose 
The purpose of this article is not to provide the 
remote sensing community with another mathematically 
air-tight dissertation on certain geodetic 
considerations inherent to any new mapping technique. 
On the contrary, the purpose is to describe a 
useful cartographic application of Landsat imagery 
and discuss empirical accuracy tests. 
As is the case with many innovations, the approach 
discussed here was born out of a problem situation 
where a practical solution was called for. The new 
method was found to be cost effective and to save 
time, while providing satisfactory mapping results. 
For that reason, I feel that the airphoto map 
control method using Landsat could be a useful and 
beneficial technique for the mapping of remote 
areas. 
1.2 Background 
During the last five years Euroconsult (a Dutch 
firm mainly active in agricultural consultancy) 
has built up considerable experience in integrated 
rural development planning in the south-eastern 
part of Irian Jaya, Indonesia. Euroconsult has 
surveyed almost half a million hectares there, and 
compiled the thematic data into maps with a scale 
of 1/20 000. 
Prior to the study, the Indonesian Government 
made available to Euroconsult blocks of unrectified 
aerial photographs not only as a source of thematic 
information, but also as a basis for mapping. The 
old Dutch maps of the region (scale 1/100 000) are 
reasonably accurate only as far as the location of 
major rivers is concerned. Geographic information 
on the interfluvial areas is completely lacking on 
these maps, which impedes their use as a mapping 
base. Other existing maps are also unsuitable for 
similar reasons. As a result, Euroconsult was 
is map accuracy. 
Landsat is thus found to be the best possible option 
be used for supporting thematic mapping data. 
obliged to produce its own basemaps. Until recently 
the best option open to the consultant to achieve 
this, was to assemble the airphotos into a mosaic 
with the help of the slotted templet method and 
then update the accuracy with the aid of traverse 
measurements. 
2 PROBLEM 
2.1 Orientation on airphotos 
Mapping which includes fieldwork in areas like 
southern Irian Jaya is, at best, a cumbersome 
exercise. Fieldwork areas are very difficult to 
reach due to lack of infrastructure. The 
environment is hostile for a variety of reasons 
such as climate, flora and fauna. 
A more serious mapping constraint follows from 
the fact that aerial photography is flown 
invariably before a start is made with fieldwork. 
As a result, locations of observations in the 
field cannot be readily identified on the 
airphotos. If the consultant cannot correlate his 
field data with the airphoto at all, then his 
airphoto interpretation is reduced to guesswork 
and the purity of his mapping units will suffer 
proportionally. Also, the accuracy of the basemap 
cannot be improved anymore. 
A primary requisite for integrated rural 
development studies is a detailed physiographic 
land-unit map covering the study area, compiled 
from airphoto interpration supported with field 
observations. The individual mapping units should 
be as pure and homogeneous as possible in order to 
serve as ’building-blocks’ for subsequent maps on 
soils, forest resources, land clearing plans, road 
alignments, village structure plans, etc. 
It is, therefore imperative that field 
observations can always be exactly located on the 
aerial photographs. To make this possible the 
airphotos must be assembled into a planimetrically 
correct photo-basemap on. which field observation