Appendix 
Survey Methods 
Area 
Estimates of forest land were determined partly 
by complete survey and partly by sampling (table 
2). Complete-survey technique was used for the 
area west of the Continental Divide, four counties 
east of the Divide, and other areas east of the 
Divide which are reserved, such as national parks. 
For the State as a whole, approximately 54 percent 
of the total area was classified as nonforest zone by 
reference to aerial photographs or by field recon- 
naissance. ‘Iwenty-seven percent was covered by 
complete surveys; 19 percent by sample surveys. 
TABLE 2.—Area of Montana forest land surveyed, by class of 
land and survey method 
Class of land Complete | Sampling | Factored Total 
survey survey out! 
Thousand | Thousand | Thousand | Thousand 
Forest: acres acres acres acres 
Commercial....... 9, 882 5 81 Lill velorereterere tats 15, 756 
Noncommercial... 2,629 BEF Ae aaceencarcc 4,076 
Reserved......... D527. isc: cravecocarorcse'| wrote (elaveelssexe 23527. 
Total ev rsistcelersce 15,038 75 B2V a | riciocvvicnare 2251359, 
Nonforesticksisters'orole-e ate 10, 230 10, 828 50,225 71, 283 
Total, all classes....... 25,268 18,149 50,225 93,642 
TU) was clirtsared: trom cia Saver areaiun. coeanivor faecal (okaeae eps 
and field examination to increase sampling efficiency. 
For the part covered by complete survey the 
determination of forest area was as follows: Cover 
types were delineated and designated by symbols 
on transparent overlays fitted to the latest base 
maps in township units on a 2-inch-to-the-mile 
scale. Intensive private and public timber cruises, 
county land classifications, cutting records, fire 
records, and aerial photographs provided informa- 
tion for the preliminary classification of most of the 
area into nonforest and forest land, the forest land 
into 10 types as characterized by tree-species com- 
position, and into 4 stand-size classes (saw timber, 
pole, seedling-sapling, and deforested) . ‘This office 
information was checked and adjusted in the field 
in connection with the mapping of the cover in 
areas for which such information was lacking. 
All forest land was further classified in the field 
into commercial and noncommercial: the com- 
mercial into 3 stocking classes, 10 age classes, and 
5 site classes. Black and white maps made from 
office tracings of the completed overlays were 
colored to emphasize type, commercial character, 
and stand-size classes. Other subclasses were dif- 
ferentiated by symbol only. A vellum overlay de- 
lineating 8 ownership classes was fitted to the 
colored base. From this combination the area of the 
various cover classes within each township was 
determined either by the use of zylonite shields 
lined in 10-acre subdivisions or by planimeter. The 
area determinations were tabulated by sections and 
checked against official Land Office totals for sur- 
veyed areas. For unsurveyed areas the summations 
were checked against the planimetered area of ideal- 
ized townships as indicated on the lastest base maps. 
For the area sampled, the population was classi- 
fied on Jl-inch-to-the-mile base maps into three 
sample categories: (1) parts inside national-forest 
boundaries, (2) parts outside national-forest bound- 
aries for which aerial photographs were available 
at less than $2 per sample, and (3) parts outside 
national forest boundaries either not covered by 
aerial photographs or for which photo costs ex- 
ceeded $2 per sample. 
The three sample categories were further stratified 
into blocks of approximately 16, 49, and 100 square 
miles, respectively, by marking Land Office section 
corners (or idealized section corners in unsurveyed 
areas) at 4-mile intervals in class 1, 7-mile inter- 
vals in class 2, and 10-mile intervals in class 3. ‘These 
marked section corners or control points were trans- 
ferred to aerial index maps from which photographs 
were selected to give detailed coverage for a 2,560- 
acre segment (4 sections) centered on each control 
56 Forest Resource Report No. 5 U. S. Department of Agriculture 
