Table. 26 
Estimation of stand mean heights on contact prints. (Errors in metres) 
  
  
Interpreter | IH IV 
| : | : 
scale | Systematic Mean sq. Systematic Mean sq. 
Scale | S I 
| error error | error error 
1:16 900 + 1.0 + 1.60 . 2.0 + 2.20 
1 : 26 000 +11 + 2.04 -21 + 2.27 
| 1 : 33 000 + 0.8 + 204 | — 1.7 + 2.29 
Table 27 
Estimation of timber supply on contact prints. Errors in % of the mean 
value (142 m3/ha). 
  
  
Interpreter IH IV 
Scale | Systematic | Mean sq. Systematic | Mean sq. 
error | error error | error 
1:16 000 + 13 + 27 14 + 34 
1:26 000 +17 + 43 12 + 37 
| 1:33 000 j +18 + 45 9 + 36 
The result is remarkably good. Both interpreters have attained 
a better estimation when using contact prints than was reached 
by means of enlarged pictures. Both estimaters obtained some- 
what better result when using the largest scale. 
One of the interpreters consistently overestimated, the other 
consistently underestimated both height and timber supply. 
In estimation of timber supply also, the largest scale has given 
somewhat better results. 
It might be expected that scale would affect the accuracy in 
the estimations more than is the case. The material is not suf- 
ficiently extensive, however, to allow of reliable conclusions. All 
the interpreters state, in fact, that contact prints at 1: 16 000 
are decidedly better than enlarged pictures at 1: 15 000 from the 
same negative. Probably the enlargement process impaires the 
pieture quality. Light reflected from high glossed pictures dis- 
turbs the interpretation work. 
34