ad 
2 
| Table I lists the field survey methods used in the determination of ground 
É control points and the accuracy required in this work. Some countries may have 
/ regions in varying stages of development for which accuracy specifications are 
different. Further, the density of ground control for the basic map scales of 
i 1:25,000 and 1:50,000 varies greatly and ranges from several points ineach stereo- 
pair to only one point in several overlaps. To the first category belong European 
countries that are covered by dense third- and fourth-order triangulation nets. 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
sien a 
  
  
  
   
  
  
  
  
  
  
  
  
i Table I 
|| Cosi Publication 5 ; ; Tolerance, 
| li ountry scale ype of ground contro tü 
| I Belgium 1: 15,000 Triangulation and closed traverses +1.0 
1] 1: 25,000 Levelling and trigonometric elevations +0.3 
j (Congo) 1:100, 000 Triangulation *2.0 
1 1:200, 000 Trigonometric elevations +1.0 
i Barometric elevations £5 to 17 
i (Congo) 1: 20,000 Triangulation +1.0 
d Trigonometric elevations 10.5 
I 
il England Fk» i255, 000 TfiangWffati etri e ions - 
| 1: 50,000 " b = a 
| barometric elev - 
Finland 1: 20,000 Triangulation 10.3 
Traverses $3.0 
| Levelling *0.1 
| | Barometric elevations +1, 0 
1 n 1:"20,000 (Planimetric points as above) 
A E 1250, 000 | 
-H I 1:100,000 Trigonometric elevations 30.3 
31! 
| 
n. | France 1: 20,000 Triangulation 2.0 
EN Trigonometric elevations 0,3 
| | 1: 50,000 Astronomical determinations 50.0 
I Barometric elevations 3.0 
i li 1:100, 000 Trigonometric points 4.0 
: 1 | Trigonometric elevations 2,0 
P 
HI 1:200, 000 Astronomical determinations 50.0 
EHI Radar altimeter 3.0 
3 i Levelling 1.0 
5 
E 
4 West 1: 25,000 Triangulation, traverses, etc. - 
1 Germany 
1 
il