6 
For highway design purposes, the accuracy of map details can be 
expressed as a fraction of the maximum scale at which the maps are 
compiled using the feasible minimum contour interval, whether done 
photogrammetrically or by using data obtained by surveys on the ground. 
Accordingly, for all maps so compiled and used in the scale range of 
1:300 (25 feet per inch) to 1:12,000 (1,000 feet per inch), the accu- 
racies required for contours and planimetric features are given in 
Table 2. 
TABLE 2 
  
ACCURACY OF MAP DETAILS 
  
Error Not Exceeding 
Proportion of Map Scale 
  
St S 
In Feet to One Inch Denominator of 
for Representative 
Fraction 
  
Details 
Tested for Accuracy 
  
90% of 
Details 
100% of 
Details 
90% of 
Details 
100% of 
Details 
  
Elevations Determined 
from Contours 
S! 
80 
S! 
ho 
m 
3,200 
S 
1,600 
  
  
Horizontal Position of 
Planimetric Features 
S? 
ho 
S? 
20 
1,600 
S 
800 
  
  
  
  
  
  
Wherever photogrammetric methods are utilized in determining the 
X, Y, and Z coordinates of supplemental control points, either by 
analog or aerial analytical triangulation techniques, the accuracies 
should conform to the stipulations recorded in Table 3.  Accuracies 
identified by the numeral (1) are generally essential for precision 
use in metropolitan areas; accuracies identified by the numeral (2) 
are generally applicable in rural areas where land uses are rather 
intense, and accuracies identified by numeral (3) are required where 
land use is not generally intense. Accuracies identified by the 
numeral (4) may be used in rural areas where topography is rugged, 
and land use is small or nil. 
In photogrammetric use of aerial photographs controlled by such 
measurements, the map scales and contour intervals should be commen- 
surate with accuracies required in position staking on the ground of 
the center line, highway structures, rights-of-way boundaries, and 
other details for constructing each highway, also in computing 
volumes of excavation and embankment and other construction quantities. 
For urban areas, topographic maps at scales of from 1:480 or 1:500 to 
1:1,000 or 1:1,200 are used, with contours of 1 foot to 5 feet or 0.3 
of a meter to 1 meter. In rural areas the topographic map scales are 
1:1,000 or 1:1,200 to 1:2,400 or 1:2,500, with contours of 2.5 feet 
to 5 feet or 1 meter to 2 meters.