3 
Table I (cont'd) 
C Publication T ; Tolerance, 
ountry scale ype of ground control à 
Netherlands 1: 25,000 Triangulation, trigonometric points, 
and and traverses t0.3 
smaller Levelling 10.05 
India 1:::25, 000 Triangulation and traverses $1.5 
1: 50,000 Triangulation and traverses 21.5 
Israel 1::20,000 Triangulation and traverses 1.0 
1: 50,000 Triangulation and traverses 1.0 
Italy 1: 25,000 Triangulation, traverses, etc. 31.5 
Vertical control $1.0 
Norway 1:,25, 000 Triangulations 1.5 
Trigonometric elevations 1 
1: 50,000 Triangulations 2.5 
Trigonometric elevations 1.5 
Switzer- 1: 25,000 Triangulations - 
land 1: 50,000 
South 1: 50,000 Mostly triangulations +1.5 
Africa Vertical control +0.6 
1:250, 000 Mostly triangulations +4.5 
Vertical control +3.0 
U.S.A 1: 20,000 Horizontal control established by ~0.07 mm 
classical and electronic means publication 
to scale 
1:250, 000 Levelling, trigonometric and ~0.1 of 
barometric elevations contour 
interval 
  
  
As for the use of photogrammetry to extend the ground control, it can be 
  
  
  
  
  
stated with satisfaction that aerial triangulation is being used as the basic method 
by every country that cared to reply to the questionnaire. An exception may again 
be found in some European countries where it is not necessary to have recourse 
to photogrammetric means in the determination of additional control because very 
excellent and dense ground control points already exist. 
In underdeveloped areas, slotted templet methods are used for the estab- 
lishment of planimetric control. In these cases vertical control may be establish- 
ed by radar profiles, by barometric field determinations, or trigonometrically.