Evaluating the need of cleaning using 3D point clouds derived from high resolution images collected with a drone

Management of young forest stands is important for the future economical outcome. Cleaning is a way to control the competition between plants and a total of 1 443 000 ha are in need of cleaning in Sweden. The cleaning is usually performed when the trees are 2 – 6 m high and the most common is to remove deciduous trees to favor coniferous species. To handle the amount of forests in need of cleaning there is a need for efficient inventory and planning of these areas. Remotely sensed data can be used to make these processes more efficient. Earlier studies have shown that variables that are commonly used for forest management planning can be accurately estimated when using photogrammetry with aerial images. In this study the use of 3D point clouds as an aid for field inventory when planning for cleaning has been evaluated. This was done by studying field inventoried sample plots and a 3D point cloud derived from high-resolution images collected with a drone in the county of Västerbotten. The need of cleaning was predicted with logistic regression with an overall accuracy of 82 %. Field attributes; average height, stem number and ΣH2 was predicted using linear regression with a relative RMSE of 43.9 %, 44.4 % and 76.2 %, respectively. The results show that it is possible to estimate cleaning need and field attributes using 3D point clouds derived from high-resolution images collected with a drone. Cleaning need can be predicted with high accuracy. The method is time consuming, hence evaluations regarding costs and time compared to manual field inventory is required if the method is to be implemented in practical use

Wildland urban interface in Sweden : a study about wildland urban interface with the fire in Sala as an example

Skogsbränder har historiskt sett varit ett naturligt inslag i den svenska naturen men idag är de starkt kontrollerade. Branden i Sala år 2014 är den största branden i Sverige i modern tid och orsakade stor materiell skada och mänskligt lidande. Wildland urban interface, det vill säga kontaktzonen mellan bebyggelse och brännbar natur, är ett stort problem i framför allt Nordamerika och Australien. Tidigare forskning kring detta för fram flera nyckelfaktorer till varför vissa konstruktioner löper större risk än andra att antändas. I denna studie har ett antal objekt studerats för att kartlägga nyckelfaktorer som kan förklara varför konstruktioner skadades eller inte vid Salabranden. Studien har baserats på en visuell analys med hjälp av flygbilder från Lantmäteriet, foton tagna av Försvarsmakten dagarna efter branden samt Skogsstyrelsens karttjänst ”brandkartan”. Samtliga studerade objekt hade mycket nära till omgivande skog och merparten hade naturliga spridningshinder i brandens spridningsriktning. Den mest avgörande faktorn för om en konstruktion skadades av branden var om en gräsmatta fanns intill byggnadens fasad. Om gräsmattan var skött runt hela byggnaden var det endast i enstaka fall som konstruktionen skadades. Förebyggande bevattning visade sig också vara ett effektivt sätt att undvika skador på byggnaden. Byggnadernas material var däremot inte avgörande för utfallet. Studien är den första av sitt slag i Skandinavien och kan ge en inblick i hur områden med liknande förhållanden som de i brandområdet i Västmanland kan komma att påverkas av skogsbränder, samt vilka förebyggande åtgärder som kan vidtas.Forest fires have historically been a natural disturbance in Sweden but today they’re strictly controlled. A forest fire in Sala 2014 was the largest forest fire in Sweden in modern time and caused great material damage and human suffering. The burnt area covered 14 000 ha and 71 buildings were destroyed. Wildland urban interface, where settlements intermix with wildland fuel, is a serious problem that applies to North America and Australia in particular. Earlier research displays many key factors determining whether some constructions are more ignitable than others. In this study a number of buildings have been studied to survey key factors on damaged and undamaged constructions during the forest fire in Sala. The study is based on a visual analysis of aerial photos from Lantmäteriet, photos taken by the Swedish armed forces shortly after the fire and the Swedish forest agencies map service “brandkartan”. All objects that have been studied are closely located to forest. The main factor determining the outcome for the construction was if a lawn was present close to the facade. Few constructions were damaged if a managed lawn surrounded the construction. Irrigation was also shown to be an effective way to avoid damage on the building. The type of building material was by contrast not a determining factor regarding the outcome. This study is the first of its kind in Scandinavia and can give an insight into how forest fires can affect areas with similar environment as the fire area in Västmanland and how to prevent damage to constructions