Background and purpose: The main goal of this paper is to inform forestry community about the latest developments in digital photogrammetry, as well as to present its possible application in forest management. For this purpose, the current state of technological development of the main tools of digital photogrammetry (digital aerophotogrammetric cameras and digital photogrammetric workstations) has been presented. Furthermore, two adjusted methods of manual digital photogrammetry for application in forest management, namely: method for strata delineation (i.e. creation of forest management division), and method for measuring stand structure elements have been developed and presented here. Material and methods: Research was carried out on the selected part of multi-aged, privately owned forest of ''Donja Kupčina-Pisarovina'' management unit which includes 6 compartments and 24 subcompartments and covers total area of 480 ha. After conducted aerial survey of research area, acquired digital images were processed, and digital terrain model and digital elevation model were derived. Digital aerial images of ground sample distance of 10 cm, topographical maps, digital terrain model and digital elevation model, as well as the digital photogrammetric workstations with appropriate software (PHOTOMOD, Global Mapper) were used for developing methods for strata delineation and stand structure elements estimation. Developments of both methods were carried out in the stereomodel of colour infrared digital aerial images in PHOTOMOD StereoDraw module. Additional data processing was conducted in Preliminary communication ArcGIS 9.1. (for strata delineation) and in Global Mapper (for stand structure elements estimation) software. Discussion and conclusions: This research has showed that PHOTOMOD Lite and Global Mapper software packages in combination with the used materials (digital aerial images, digital elevation model) and digital photogrammetric workstation completely satisfy the needs for strata delineation and stand structure measurements. The PHOTOMOD software enables simple creation of projects of digital images, easy manipulation of multiple digital images, and many other features that facilitate photogrammetric measurement and photo-interpretation, but its free version PHOTOMOD Lite has limited capabilities in terms of number of images and quantity of vector data that can be processed. If digital images of high spatial resolution are used (e.g. 30 cm or better), as was the case in this research, stereo-effect experienced by the operator and the quality of photo-interpretation are very good. That enables clear determination of vegetation types and as well as single tree species, more accurate pinpointing of tree tops and more accurate delineation of tree crowns. As long as automatic procedures are not available, digital photogrammetry has to rely on manual methods. Allometric relation between variables measured with photogrammetric method and desired variables need to be developed. An attempt to address this issue, at leas...

Urban Heat Island (UHI) is a phenomenon specific to urban areas where higher air temperatures manifest in the city area in relation to its surrounding rural landscape. Currently, UHI is one of the most dangerous environmental conditions for cities as well as their residents. It is expected that the intensity of UHI will increase with climate change. This work presents an analysis of the UHI phenomenon for the City of Zagreb, Croatia in the summertime period 2013–2022. In order to explore UHI, Land Surface Temperature (LST) was calculated using Landsat 8 (OLI TIRS sensor) satellite imagery. After the delineation of UHI, calculated temperatures were put in relation to NDVI (Normalised Difference Vegetation Index) and NDBI (Normalised Difference Built-Up Index) indices for the study area. Results show the similarity of mean temperatures over the observed period. However, the influence of external variables on UHI’s spatial expression was observed. Forest-covered areas and other green parts of the city’s infrastructure express the lowest temperatures, while built-up sites are the hottest points in cities. Results confirm the importance of urban green infrastructure for resilient cities and present the results of a long-term UHI observation in a Southeast European city.

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Negativne posljedice propadanja šuma nastoje se umanjiti provođenjem gospodarskih mjera i praćenjem zdravstvenog stanja stabala, odnosno procjenom oštećenosti krošanja. Utvrđivanje zdravstvenog stanja šuma provodi se, osim terestričkim načinom, i metodama daljinskih istraživanja – interpretacijom infracrvenih kolornih (ICK) aerosnimaka. Inventarizacija oštećenosti šuma pomoću aerosnimaka temelji se na ustanovljavanju stupnja oštećenosti pojedinačnih stabala (krošanja), uz kvalitetno izrađen fotointerpretacijski ključ. Na temelju provedene fotointerpretacije infracrvenih kolornih (ICK) aerosnimaka, mogu se odrediti pouzdani statistički podaci o oštećenosti šuma. Inventarizacije oštećenosti šuma na ICK aerosnimkama do sada su se provodile fotointerpretacijom analognih aerosnimaka na analitičkim stereoinstrumentima. Napretkom tehnologije analogne snimke su zamijenjene digitalnim, analitički stereoinstrumenti - digitalnim fotogrametrijskim stanicama, a interpretacija se obavlja u programu na zaslonu računala. Osnovni cilj istraživanja bio je usporediti rezultate procjene oštećenosti krošanja na analognim i digitalnim ICK aerosnimkama istoga područja, zbog čega je bilo potrebno aerosnimke iz 1989. godine skeniranjem prevesti u digitalni oblik, te digitalne snimke iz 2008. godine prevesti u analogni oblik. Za dio gospodarskih jedinica Josip Kozarac i Opeke, provedena je interpretacija analognih i digitalnih aerosnimaka iz dva perioda snimanja (1989. i 2008. godina). Na svakoj točki rastera 100x100 m procijenjena su 4 najbliža stabla (krošnje) te izračunati pokazatelji oštećenosti (O, SO, IO, SO₁) za pojedine vrste drveća, za sve interpretirane vrste zajedno, po prugama snimanja, te ukupno za područje istraživanja. Na temelju izračunatih pokazatelja oštećenosti, dobivenih interpretacijom analognih i digitalnih snimaka iz 1989., te 2008. godine, utvrđeno je da između rezultata ne postoji značajna razlika s obzirom na procjenu zdravstvenog stanja stabala (oštećenosti krošanja). Time su poboljšane postojeće metode procjene zdravstvenoga stanja i ukazano na mogućnosti primjene digitalnih ICK aerosnimaka u šumarstvu.

© iForest -Biogeosciences and Forestry IntroductionThe narrow ecological niche and the extensive exposure to pollution makes silver fir (Abies alba Mill.) a highly endangered species. It is currently the most damaged tree species in Croatian forests (Prpić & Seletković 2001, Potočić et al. 2008. In addition to insects and fungi, fir is increasingly attacked by mistletoe (Viscum album L. ssp. abietis [Weisb.] Abrom), which physiologically weakens the tree by its remarkable consumption of water (Fisher 1983, Lamont 1983, Ehleringer et al. 1986) and mineral nutrients (Watson 2001), thus predisposing the host to pest and disease attacks. Mistletoe is also considered an indicator of existing stress (Atzberger & Werner 1998, Smith et al. 2004, Moorthy et al. 2008, Wang & Li 2012. It has been reported that an excessive number of shrubs may even cause tree death (Plagnat & Brossier 1969, Cervera & Villaescusa 1977, Zuber 1983, Chéret et al. 1987, Tsopelas et al. 2004, Olivia & Colinas 2007. Morevover, mistletoe-infected trees have lower increment than uninfected trees (Klepac 1955, Uščuplić 1992, Uščuplić & Dautbašić 1998, Noetzli et al. 2003, Barbu 2009) and should therefore have a cutting priority as long as their timber still retains its commercial value. A high correlation between fir infestation and mistletoe distribution has been reported (Hofstetter 1988, Idžojtić et al. 2008, Barbu 2009) with an almost exponential trend in the mistletoe population increase (Noetzli et al. 2003). An increase in the intensity of mistletoe infestation was also noted, favoring its spread to healthy trees (Idžojtić et al. 2003). Tree health status can be determined in two ways: by ground and by remote sensing observations, of which color infrared (CIR) images are particularly important (Pernar 1997, Pernar et al. 2007a. In Croatia, forest damage over large areas has been assessed by means of CIR aerial imagery since 1988, though mistletoe could not be detected based on these images. Preliminary pilot tests aimed at assessing fir damage using multispectral digital images have been carried out in (Pernar et al. 2007b), confirming that mistletoe could be successfully detected using a high-resolution multispectral digital camera. In contrast, standard field methods for mistletoe detection are generally based on visual survey (using binoculars) of edge trees along roads or in clearings, from which only the upper crown is visible (Idžo-jtić et al. 2005), and therefore do not often reflect the real conditions in the field. For example, Diminić et al. (2011) suggests that ground analyses of mistletoe presence in the crowns of standing trees are not fully reliable.The limitations of standard field methods call for new approaches to assess tree health and quantify mistletoe infestation. The importance and efficiency of high-resolution multispectral and hyperspectral imagery for the goals mentioned above have been highlighted by Entcheva-Campbell et al. (2004), Somers et al. (2010) and Cho et al. (2012). By recording a high number of narrow ban...

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Svi objekti reflektiraju, apsorbiraju ili emitiraju elektromagnetsko zračenje ovisno o sastavu, stvarajući jedinstvene uzorke koje zovemo spektralni potpisi ili endmemberi. Čisti spektralni uzorci definiraju se u idealnim terenskim ili laboratorijskim uvjetima, gdje je spektar refleksije dobiven uporabom spektroradiometra fokusiranog na jednu površinu. Prema istraživanjima, većina spektralno čistih uzoraka odnosi se na istraživanja minerala. Spektralni potpisi vegetacije, za razliku od spektralnih potpisa minerala, su dinamični (u spektralnoj, prostornoj i vremenskoj rezoluciji), znatno zahtjevniji za prikupljanje i dokumentiranje, te ih treba s oprezom ugraditi u spektralne knjižnice. Postoji nekoliko spektralnih knjžnica (većih i manjih) koje su organizirane po poglavljima, a sastoje se od uzoraka koji imaju dovoljan broj analiza i dokumentaciju za utvrđivanje kvalitete spektra. U ovome istraživanju izdvojeni su spektralni potpisi za nekoliko vrsta u Hrvatskoj: hrast lužnjak (Quercus robur L.), običnu bukvu (Fagus sylvatica L.), običnu jelu (Abies alba Mill.), običnu smreku (Picea abies L.), bijelu imelu (Viscum album L. ssp. Abietis (Weisb.)) i žutu imelu (Loranthus europaeus Jacq.). Svrha istraživanja je bila uspostaviti spektralnu knjižnicu za buduća istraživanja primjene hiperspektralnih skenera pri detekciji vrsta drveća. Za prikupljanje spektralnih potpisa korišten je hiperspektralni linijski skener ImSpector V9, koji snima vidljivi i bliži infracrveni dio spektra od 430 do 900 nm. Osim njega korišten je i senzor sunčevog zračenja FODIS, kako bi dobili prosječnu vrijednost sunčeve insolacije u trenutku snimanja. Snimanje je provedeno u kontroliranim uvjetima. Uzorci su postavljeni na kružnu podlogu sa naznačenom podjelom za svakih 45 stupnjeva točno u centru optičke osi skenera, te su rotirani kružno. Spektralne snimke su zatim obrađivane u softveru ImageJ gdje su izdvojeni podaci za daljnju analizu. Nakon obračuna srednjih vrijednosti po vrstama napravljene su usporedbe između vrsta. Dobiveni rezultati pokazali su preklapanja u vidljivom dijelu spektra, dok u bližem infracrvenom dijelu spektra vrste diferenciraju jedna od druge, odnosno rezultati pokazuju kako postoji razlika između spektralnih krivulja uzoraka. Provedenim istraživanjem definirani su postupci uzimanja uzoraka i dobiveni spektralni potpisi za istraživane vrste (endmemberi). Spektralni potpisi postali su dio spektralne knjižnice, a najznačajniji rezultat istraživanja je mogućnost primjene za detekciju vrsta na hiperspektralnim snimkama.