GVII-72 
PHOTOGRAMMETRIC ENGINEERING 
statistical methods in evaluating geologic maps. It is the purpose of this paper 
to present the general procedures for evaluating photo interpretation in terms 
of the accuracy of the designation of a map unit, and the accuracy of the loca 
tion of the boundary lines between map units. 
Methods 
Descriptions of the map symbols, type of photography, soil type photo 
patterns and field checking methods have been omitted purposely to avoid 
complicating the presentation of procedures involved in the quantitative 
evaluation of photo interpretation and map accuracy. Principles and procedures 
will vary for different types of photo interpretation studies. The five general 
phases in the preparation of an engineering soils map* * of the Bangor Quadrangle, 
along with the collection of data necessary for the evaluation, are as follows: 
A. The making of a field reconnaissance with photos in hand to determine 
the significance of various soil patterns and photo elements in order to 
develop a set of diagnostic features. 
B. The delineation of soil type boundaries by photo interpretation in the 
office. 
C. The field checking of the soil type designations and the accuracy of the 
location of the boundary lines. 
D. The transference of photo detail to a base map. 
E. The spot checking of the map in the field to determine the accuracy of 
the final product. 
While in the field (Step C above) a record was maintained of the photo 
interpretation classification and the field classification of 449 sampling locations 
(Table II), and interpretation errors in designation and location of boundary 
lines were rectified. For this study, the number of areas of each soil type was 
Table I 
Engineering Soils Information, Bangor Quadrangle, Maine 
Map Unit 
Total Acreage 
Number of Areas 
Av. Acreage/Area 
R 
14,050 
493 
28.5 
BG 
14,770 
131 
112.7 
B 
48,200 
152 
317.1 
G 
3,280 
135 
24.3 
F 
34,200 
96 
356.3 
S 
7,970 
294 
27.1 
P 
5,400 
43 
125.6 
wt 
6,630 
11 
602.7 
134,500 
1,355 
t Signifies water which does not appear in other tables and in the discussion. 
counted and the acreage of each type was determined by use of a dot grid with 
16 dots to the inch. Data for the Bangor Quadrangle, Maine, an area of 134,500 
acres or approximately 210 square miles, are summarized in Table I. Map unit 
symbols represent soil types recognized in the Maine Reconnaissance Engineer 
ing Soils Classification System. Minimum area mapped for this study was five 
acres. 
* The Maine Reconnaissance Engineering Soils Classification System was developed by E. G. 
Stoeckler as a part of a photo interpretation project financed by the Maine State Highway Com 
mission in cooperation with the U. S. Bureau of Public Roads.