Ajuourhållning av ungskogsdata med hjälp av digitala flygbilder
The purpose of this study is to investigate whether it is possible for SCA to update their stand register with use of digital aerial photos photographed with a Zeiss/Intergraph DMC. ?Updating? in this study implies the delineation of stands and estimating stand variables such as average stand height, volume density, stand volume, and tree species composition in order to identify stands which can be of current interest for thinning.
The study also includes how the aerial photo material and experience of the interpreter can influence the quality of the interpreted variables.
The aerial photo interpretations were made by both experienced and inexperienced interpreters. The inexperienced interpreters consisted of staff from SCA with forest knowledge and also Master of Forestry students from SLU.
The experienced interpreters underestimated the average stand height between 1 and 1.3 meters compared with the field inventoried stand height. The standard error from the measurements was between 0.8 and 1 meter. The experienced aerial photo interpreters together measured average stand height with a systematic underestimation of around 1 meter.
The inexperienced aerial photo interpreters had a standard error between 1.2 and 2.4 meters and had a greater distribution compared with the experienced interpreters. All together as a group there was no systematic error in their interpretations.
Conclusions
? The experienced interpreters showed better results when measuring average stand height.
? The experienced interpreters showed systematic errors when measuring average stand tree height. Their errors were relatively small.
? The inexperienced interpreters, as a group showed no systematic errors in their interpretations.
? The two experienced interpreters both over- and under-estimated stand volume, respectively.
? The results from interpreted tree species composition were better in the digital photos as compared to the scanned analog photos.
? Site index was under-estimated by both the experienced and the inexperienced interpreters.
? There was no positive effect from training among the inexperienced interpreters except in the case of interpretation of volume density.
? Photo interpretation made by inexperienced interpreters will probably provide adequate results, with additional training, which can result in a good possibility of updating stand values and furthermore identify potential thinning stands.