This study focuses on forest monitoring at landscape level on the basis of a methodology combining satellite data mapping and image morphological processing. It aims to contribute to reporting on trends of forest fragmentation and connectivity, by using forest spatial pattern metrics. The Carpathians were selected as a study area.
For five case study areas single-date forest - non-forest maps derived from Landsat images acquired in the 1980s and 2000s were an input for the post-classification change detection. Morphological image processing was applied then to map forest spatial pattern into six classes (core, patches, edges, perforation, connectors and branches). Further, connectivity and fragmentation processes were assessed on the basis of the proportion of forest pattern classes.
We found a general trend of forest increase over the last decade. An increase of forest fragmentation and connectivity was noticed for four case study areas and a decrease for one case study area. The increase of forest cover may indicate the decline of importance of mountain agriculture, while changes of forest fragmentation and connectivity are probably related to the transformation of forest management practices in the 1990s in the region. We conclude, that the proposed methodology allows assessing trends in forest fragmentation and connectivity at approximately 1 ha minimum mapping unit.
A Graphical User Interface (GUI) based software package has been designed to detect and statistically analyze illicit oil spills in European Seas. The first part of the tool allows for reading and processing of multiple formats of SAR satellite data for edge detection and shape analysis and stores the spill features in a database. The second part of the tool is used to display and perform statistical analysis on the previously established database.
The method combines the use of a standard radiative transfer code (UVspec) and various sources of information on the influencing parameters to map surface UV radiation. GOME, TOMS or TOVS data are used for the total column ozone. The cloud optical thickness is estimated using METEOSAT/MVIRI data. Other influencing factors taken into account include tropospheric aerosols, snow cover and surface elevation. The resulting products are maps of surface dose rates and daily doses, covering Europe with a spatial resolution of 0.05 deg. Because the method is using METEOSAT the cloud optical thickness can be estimated every half-hour. This allows quantifying how well doses can be reconstructed from one or a few cloud images per day. The method is now being used to reconstruct the surface UV conditions during the last 10 to 15 years, in particular to support a study on the effects of UV radiation on marine biology in the Northeast Atlantic. Initial results for the month of March, from 1990 to 1999 are presented. Their validity is discussed with respect to the consistency of the input data during this period. A scheme to deal with drifts in METEOSAT sensitivity is presented.
The interpretation of the reflected radiation measured by wide angle instruments or in off-nadir directions requires the knowledge of the bi-directional reflectance distribution function (BRDF). By using atmospheric radiative transfer calculations we demonstrate how several vegetation indices are influenced by the BRDF and by the atmosphere. We present two methods to retrieve the leaf area index (LAI) using bi-directional reflectance factors in the near infrared spectral domain. Firstly we use a newly defined Off-Nadir Vegetation Index (ONVI) and a multiple regression analysis. The method was tested on a synthetic data set with a LAI varying between 0 and 10. We achieved a root mean square error of 1.54. Secondly we trained a neural network with synthetic data computed with the BRDF model of Roujean et aL Using observations in backward scattering direction the root mean square error for LAI retrieval was 1.2. To obtain more comprehensive information on the characteristic and stochastic properties of the BRDF a new measuring method was developed. It employs a rotating CCD-line camera mounted on an extendible boom. The data of our field campaigns together with the measurements performed by other groups are arranged in a BRDF catalog.