(408) 
Many will agree that the use of precision plotting machinery for this type of 
work is inconvenient and time consuming. At the Directorate of Colonial Sur- 
veys it is found perfectly adequate and very much cheaper to break down our 
network with slotted templates, possibly assisted by radar or a small amount of 
subsidiary ground survey, and to survey the 50 or 100 foot contours with multi- 
plex based on spot height control generally obtained by aneroid traverse. Modern 
survey aneroids are nowadays so good that when properly used they can be 
relied on to provide height control sufficiently accurate for contours at these 
intervals, at a very low cost. 
Having dealt with undeveloped countries, let us now see what happens 
when a country begins to develop. The first developments are usually very local, 
and there arises a requirement for small areas of mapping at a larger scale. The 
scale and accuracy of these small surveys is governed entirely by the purposes 
for which the maps are to be used. No standard technique for this work can be 
laid down as there are so many factors to be considered. Precision plotting 
machines are used sometimes but there is no prejudice in favour of Precision 
Plotting machines or anything else. The aim is to choose the cheapest method to 
satisfy the requirements. 
Later, when a country has progressed sufficiently to justify extensive map- 
ping at a larger scale, a closer network of accurately established points must be 
obtained. 
Under these circumstances, it is reasonable to suppose that its general com- 
munications will have improved and it becomes easier for the surveyor to get 
about; this does not mean to say that photogrammetric control extension will 
not be used, but that improved communications may make other methods more 
economical. An attempt must be made to choose the most economical method, 
keeping an eye on future needs, amongst which is the cadastral survey, which 
requires the fixation of a large number of points permanently marked with 
survey pillars on the ground. 
4. General considerations with regard to the use of precision plotting 
instruments. 
In my opinion it is only at the larger scales that the use of precision plotting 
instruments is a technique worth employing. At small scales, the accuracy with 
which these instruments can undertake control extension or delineate the detail 
is unnecessarily great. This would not in itself be a disadvantage, if it did not 
result in excessive slowness of operation. Much more rapid alternative techniques 
are available with less, but quite sufficient accuracy. 
At large scales however, where the majority of the detail is shown to scale 
without conventionalisation, there is no doubt that the precision plotting instru- 
ments provide the most accurate, and where the detail is at all congested also the 
most rapid, basis for detail plotting from air photographs. I would not however, 
go so far as to say that the use of plotting machinery for this type of work is 
justified in all circumstances. Where one is concerned to map property bounda- 
ries which do not conform to physical divisions, or where much detail is hidden 
under trees it must be carefully considered whether it is economically justified 
to use photogrammetric methods for supplying that part of the detail which can 
be seen on the photographs whilst the remaining detail is supplied on the ground, 
or whether it is not more economical to use ground methods exclusively.