DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu
| ŠUMARSKI LIST 7-8/1966 str. 15 <-- 15 --> PDF |
4. Sa istog stajališta treba izmjeriti elevacione kuteve na sredinu visinskog prirasta (ßi) i na sredinu letve (ß~>). Kod toga se može upotrebiti svaki jednostavniji padomjer (npr. hipsometar Blume-Leiss ili Haga). B. Rad u laboratoriju 1. Izraditi kopije slika vrha i letve sa istim povećanjem. 2. Fotografija letve može se sada koristiti kao mjerilo kojim treba izmjeriti fotografiju visinskog prirasta. Kod toga treba namjestiti mjerilo tako da sredina letve koincidira sa sredinom visinskog prirasta. C. Obrazloženje (Vidi sliku 1) Budući da su veličine slika jednake (tj. slika od a jednaka je veličini slike od b. jer smo sliku letve upotrebili kao mjerilo), to su i vidni kutevi jednaki tj. m — a-2. Prema tome COS2/Jl COS2/?2 COS2/?2 a = b = a = b — 1 1 COS2^! Veličinu visinskog prirasta (a) dobit ćemo tako da fotografijom letve izmjerimo fotografiju visinskog prirasta i tako odredimo b, te taj iznos pomnožimo sa faktorom cos2/?ä/cos2/?i. Primjeri: vidi slika 2. A PHOTOMETHOD FOR THE MEASUREMENT OF HEIGHT INCREMENT Summary Some forest tree species form each year one whorl. The distance between tv\o consecutive whorls is identical to the one-year height increment. This increment can optically be measured by precision instruments (e. g. with the theodolite or Lilienström´s dendrometer), but working with such instruments is tedious and time-consuming and therefore expensive, while the instruments themselves are dear. By means of the pnotomethod it is possible tc simplify the work in the field and to make it cheaper (although a little more laboratory work is needed). A. Work in the field 1. By means of a binocular (or with the naked eye) it is necessary to choose a tree whose top and several whorls (i. e. the height increment of one or several years) are visible. 2. A centimetre or decimetre graduated rod should de loaned against the stem, so that it stands in the vertical line with the tree top. 3. With a miniature camera (24 24 mm or 24.36 mm) equipped with a slightly longer focal length (e. g. Leica-size 24´36 with telephoto lens f = 13,5 cm) it is necessary to take a picture separately of the tree top (the top with some whorls i. e. an increment of several years) and separately of the rod leaned against the tree base, from the same position. 4. From the same position it is necessary to measure the elevation angles towards the middle of the height increment (ßi) and towards the middle ot the rod (ßi). In this work any simple clinometer (e. g. Blume-Leiss or Haga hypsometers) can be used. Laboratory work 1. To make a copy of the pictures of tree top and rod with the same enlargement. 2. The photograph cf the rod can now be used as a measuring scale by which the photograph of the height increment should be measured. In so doing the measu |