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The methods of surveying and calculating.
The second National Survey of the forests of Finland was carried
out, as already mentioned in the preface, during 1936—1938. The
detailed plan of work was published in volume 22 of the publications
of the Forest Research Institute.
The survey was made by the line-survey and circular sample plots
method. Survey-lines were drawn across the country from SW to NE
(see map on p. 8). In South Finland and Central Finland the
intervals between them were 13 km, up to about 65° N. lat., further north
26 km and on Ahvenanmaa (Åland) 10 km. Along these lines a separate
survey was regularly made for each land figure and forest stand
crossed by the line, and at the end of each kilometre a sample plot was
measured and studied in detail. The sample plots were limited to 10
ares and were circular in shape with a radius of 17.844 m.
The total length of the survey lines was 24 619.35 km and the
number of complete sample plots measured on the lines 14 058. The
number of land figures and forest stands on the survey lines was
177 309, and the number of survey forms employed as material for
study was consequently the same. The original material also
consisted of 14 058 forms representing as many sample plots studied in
detail and 1 971 similar forms of sample markings, besides several
thousand research forms for studying the periodicity of growth. The
research material was worked up and the results were calculated
partly during the intervening winters, but the work was only fully
under way after the last summer of field work in October 1938.
The line survey forms were drawn up from the very first with a
view to making the calculations to be based on them as far as possible
by the »punched card system» on Hollerith statistical machines. All
the numerical data contained in the 177 309 survey forms were recorded
by the punching machines on punched cards, the number of which
was consequently also 177 309. This work was checked by
controlling machines and it was only after this that the survey material
was ready for further use. The next task was to group the cards
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