66 
periodical adjustment of the instrument required about 20 hours extra time which 
could have been saved if it had been possible to perform the instrumental work at 
one time. 
4. Quality of the Ground Control Points and The Test Points. 
A considerable number of test points could not be identified with sufficient re 
liability. A glance at the available sketches of the ground control points and test 
points shows part of the trouble. These sketches are in some cases rather poor. Also, 
the fact that the descriptions of these points are in French caused some identification 
errors due to the fact that the knowledge of the French language of the personnel 
performing the block triangulation is rather limited. 
A certain number of test points were off or could not be identified and were, 
consequestly, omitted (designated as N1), while for other test points the identification 
was considered as questionable (designated as IQ). 
N1 points (omitted points) are: 
16, 23, 44, 45, 46, 57, 58, 71, 74, 75, 76, 93, 110, 114, 115, 116, 117, 138, 151, 152, 
185, 195, 196, 197, 211, 232, 233, 234, 235, 247, 250, 253, 260, 266, 269, 270, 285. 
For some other test points the measurement of the elevation could not be com 
pleted with sufficient reliability. Therefore, no elevations were recorded for these 
points. 
Points with non-recorded elevation are: 
51, 64, 66, 67, 70, 81, 86, 94, 96, 102, 111, 149, 163, 172, 215, 268. 
IQ points (questionable points) are: 
9, 13, 14, 24, 27, 29, 60, 68, 126, 136, 142, 167, 207, 290, 291. 
The identification was considered as poor for a considerable number of other 
ground control or test points. The resulting « smaller identification errors » could 
be avoided if well identifiable or signalized ground control and test points would be 
available. These smaller identification errors certainly affected the accuracy of the 
block triangulation « Massif Central » and it is to be feared that the determined errors 
of the test points do not reflect the inherent accuracy of the block triangulation method 
applied. 
The fact that the identification for many test points was found as poor was also 
the reason for the selection of a much larger number of ground control points used 
for the block adjustment (see Fig. 1) when compared with a similar block triangulation 
with well identifiable ground control points. It was anticipated that the use of such 
a large number of ground control points for the adjustment of the block triangulation 
would reduce the effect of the errors due to poor identification upon the block trian 
gulation. 
5. Experience of the Personnel. 
As in most scientific and technical operations the performance of a block trian 
gulation i. e. its quality and accuracy depends to a considerable extent, on the degree 
of experience of the personnel involved. If the degree of experience is classified as 
« little », « average », and « extensive », then the personnel who performed the block