+ à 
These surveyors, who depended upon surface transport, 
established map control for about 25 per cent of the Island, and 
the surveyors of the Army Survey Establishment for about 5 per 
cent. In addition, a helicopter-equipped party of Topographical 
Survey was employed for two months in 1951 and four months in 
1952 and during these periods secured map control for approxi- 
mately two-thirds of the Island. 
Surveys by the Hydrographic Service, undertaken in con- 
nection with charting activities, proved a valuable addition, and 
the great advantage and satisfaction of being able to start map- 
ping control from triangulation stations of the Geodetic Survey 
was an important factor in this project. 
When map compilation commenced in October 1949, the 
Topographical Survey was engaged in training personnel with the 
right type of eyesight to operate its recently acquired multiplex 
units. Since these were the first stereo-plotters employed by 
the Survey, it is not surprising to find that as the work pro- 
gressed many changes were made in photogrammetrical and 
associated compilation techniques. These changes in procedures 
were introduced in stages as experience and confidence were 
gained. Much useful information, freely given by those engaged 
on similar work in the United States, was assimilated. The 
history of these developments can be foilowed best by explaining 
the methods used on the different blocks of maps compiled. 
The first map sheets to be compiled consisted of a block 
of ten in the Bonavista-Trinity Bay area. Initially, the work 
was complicated by a change in the method of plotting co- 
ordinates, the old system of plotting by geographical position 
being superceded by the rectangular co-ordinate system. The 
advantages of this new system with Transverse Mercator Co- 
ordinates soon became apparent, and these maps were plotted 
by the conventional multiplex bridging method at a scale of 
1:16,000. Horizontal control was required at each end of the six 
or seven overlap bridges, and vertical control at both ends and 
in the middle. After adjustment on the multiplex tables, the 
operators plotted map detail in pencil on gridded paper plots. 
These plots were subsequently inked, mounted on metal sheets 
and photographically reduced to 1:40,000 scale. Contact paper 
positives were then mounted with rubber cement on gridded paper