Current issue: 56(2)
Under compilation: 56(3)
In connection to the Third National Forest Inventory of Finland, two survey strips in the northernmost Finland were photographed on scale 1:15,000. Infrared films and a yellow filter were used. For the present experiment a total length of 66 km of the strips was photographed. The strips were surveyed visually from the ground by stands. Sample plots were measured at kilometre intervals. The aerial photographs were surveyed the distances covered in the ground. The work was aided by stereograms which showed 16 large-size sample plots localised on aerial photographs.
The main groups of land identified along the survey line were productive and poorly productive forest land, wasteland and another land, in addition, peatland and firm land were distinguished. Although some differences were noted, the two survey methods provided fairly similar results. For an estimation of the tree species composition the material is one-sided since the district is mainly Scots pine. The principal tree species was successfully distinguished on aerial photographs in 78 out of 82 comparable pairs.
The mean of ground observations of dominant height of the stands was 10.9 m, that of observations on aerial photographs 11.2 m. The result of stand volume estimates reveals a distinct correlation between the various methods of estimation.
In an earlier study it was shown that it is possible, using a stand volume table based on characteristics revealed in aerial photography, to create a general idea of stand volume on the southern half of the country. A few additional factors, of interest for the stratification necessary in forest inventories, were also studied. A distinct correlation was observed between the results of aerial and ground survey for all the characteristics discussed. The present experiment showed that the prerequisites for stratification through aerial photographs do exist. Further investigation is needed into the most appropriate methods for stratification in each situation.
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