Data collection
Data are collected by two different methods: aerial photo interpretation and field inventory.
Aerial photo interpretation
The composition and structural changes in the landscape are large scale events that are hard to detect from the ground, but that can easily be interpreted from infrared aerial photos. A general interpretation and digitizing is made of the NILS plots. Many different types of landscapes are registered in order to give a general picture of the structure and composition of the landscape. Within a kilometer square (1x1 km), a more detailed interpretation with digital readings of landscape elements and biotopes is made. Interpretation and analysis of historical aerial pictures and maps makes it possible to follow the historical development.
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Field inventory
Field inventory crews document the central 1 km x 1 km squares. The field inventories are performed to supplement the aerial photo interpretation, but also to specifically monitor objects, structures and species that cannot be detected or interpreted frpm the aerial images. About ten two-person crews take part in the the fieldwork, which is performed between May and September.
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