Application of Aerial Photographs in Forest Management in Croatia

U uređajnoj inventuri šuma u Hrvatskoj koriste se isključivo te­restričke metode prikupljanja podataka, koje iziskuju velik utrošak vremena i radne snage, a samim time i značajna novčana sredstva. Primjenom metoda daljinskih istraživanja smanjuje se terenski rad, što otvara mogućnost ušteda vremena i novca. Iako su posljednjih tridesetak godina provedena različita istraživanja o mogućnostima primjene daljinskih istraživanja u šumarskoj praksi, klasične fotogrametrijske metode nisu našle širu praktičnu primjenu u uređivanju šuma. Razvojem digitalnih aerofotogrametrijskih kamera i digital­nih fotogrametrijskih stanica ponovno je otvoreno pitanje mogućnosti pri­mjene fotogrametrije u praktičnom uređivanju šuma. U radu je dan pregled dosadašnjih istraživanja i rezultata primjene aero­snimaka na poslovima uređivanja šuma u Hrvatskoj. Prikazano je trenutno sta­nje razvoja tehnologije na području digitalne fotogrametrije, te nekoliko odabranih istraživanja u kojima se opisuju mogućnosti i ograničenja primjene suvremenih fotogrametrijskih metoda u uređivanju šuma u Europi i svije tu. Cilj rada je pružiti doprinos u određivanju smjernica za primjenu aerosnimaka u praktičnom uređivanju šuma u Hrvatskoj. Jedno od područja gdje se ponaj­prije može očekivati primjena aerosnimaka u uređivanju šuma u Hrvatskoj su područja privatnih šuma, za koja još ne postoje programi gospodarenja.In forest inventory, in Croatia, data acquisition is performed using exclusively terrestrial methods which are costly and time consuming. With application of remote sensing methods, the need for the field work is re­duced which might open the possibility of reducing costs. In the last thirty years various research about possibility of applying remote sensing methods in practical forestry in Croatia were conducted. But, practical applications of data obtained by remote sensing methods were limited mainly to their use for the orientation in the field. Classical photogrammetric methods were one of the methods that were te­sted, but also did not find wider application in practical forest inventory. Ho­wever, development of new digital image acquisition and processing technology has encouraged us to reconsider the application of digital photo­grammetry in the forest inventory. The aim of this work is to give contribution in determining the guidelines for application of aerial photographs (digital images) in practical forest management. In the last thirty years photogrammetry developed from analogue, over analytical to digital photogrammetry. Film based aerial photographs are still used in analogue and analytical photogrammetry, and photointerpretation is performed with analogue or analytical stereoinstruments. In digital photo­grammetry film based aerial photographs are replaced with digital images, and photointerpretation is preformed using specialized computer 3D monitor. In the last decades, digital aerophotogrammetric camera (Figure 1) and digi­tal photogrammetric workstation (Figure 2) became the most important tools of digital photogrammetry, especially in geodesy. In this paper we presented the overview of the past research and results of application of aerial photographs in forest management in Croatia. Research of stand delineation, tree and stand attributes, and other application of aerial photographs in forest management are presented. Most of those researches were carried out with photointerpretation and photogrammetric measure­ments on film based aerial photographs with analytical stereoinstruments. However, several pioneering researches using digital image analysis were re­viewed here as well. We presented the current state of the technology in the field of digital pho­togrammetry. Also, a review was given of several selected research from Eu­rope, which described the possibility and limitations of application of modern photogrammetric methods in forest management. Overview of domestic and foreign literature indicates that an application of digital images of high spa­tial resolution, which can be obtained from digital aerophotogrammetric ca­mera for use at digital photogrammetric workstations, are insufficiently explored, especially for application in forest management. One possible area of application of digital photogrammetry in Croatia is in the management of private forests. Because of the lack of proper management and of inventory data for private forests, we can assume that digital photogrammetry could prove useful in this area of forestry. This could lead to reduction of the requi­red field work and related costs in creating forest management plans. In addi­tion, when obtained, high resolution digital images of forested area are an important document that could be used in future (research and monitoring of growth, forest health, harvesting, etc.). Should costs in data acquisition for fo­rest inventory by employing digital photogrammetry prove to be lower (or in worst case only slightly higher) that those employing classical methods, this should be a strong sign to the forestry community in Croatia to consider the use of digital photogrammetry in forest management