Forest resource information is collected using a method that utilizes sample plot measurements as well as laser scanning from an aircraft and aerial photography. In 2020, the second remote sensing-based inventory round covering the whole of Finland began, which is proceeding in accordance with the National Laser Scanning and Aerial Photography Programme. The programme is coordinated by the National Land Survey of Finland.
Laser scanning and aerial photography are both needed for forest inventory. Finland's comprehensive laser scanning will last for six years and the last areas will be scanned in 2025. In the aerial photography programme, the areas will be photographed every three years, that is, the areas will be photographed in the same year as laser scanning and for the second time in the middle of the laser scanning cycle. In northernmost Lapland, the laser scanning and photographing cycle is half as slow.
Laser scanning provides accurate and three-dimensional information about the structure of trees and terrain. Laser scans are performed from an altitude of 1.5–2 km and the point density used is 5 observation points per square meter. In addition, aerial photographs are used, for example, to identify tree species. Aerial photographs are taken from an altitude of 7–8 km and terrain accuracy is 40 cm.
A single remote sensing area has a total area of about 300,000 hectares, of which more than half is forest, depending on where in Finland the area is located. Approximately 22 areas from different parts of the country are surveyed annually and 3.5–4 million hectares of forest are inventoried. The statutory task and the focus of the Finnish Forest Centre’s activities is to collect information on private forests, but basic inventory information is produced comprehensively from all forests.
Information is processed from the inventory data
The collection and processing of forest resource data based on remote sensing takes a year.
In the first spring and summer, laser scanning and aerial photography are performed, and sample plot areas are measured in different types of forests for tree interpretation modelling. From one inventory area, 700–800 circular sample plots or 150–200 new types of larger tree map sample plots are measured. Different plot types can also be combined.
In the autumn, the information required for tree interpretation is pre-processed, and in the winter season, statistical calculation models are prepared, the functionality and the quality of the results of which are ensured by comparing them with the data measured in the terrain. The actual tree stand interpretation is done by specialized remote sensing companies.
The inventory unit for tree stand interpretation is a 16 x 16 m grid square, as in the previous round. The standard grid covers the whole country and is a separate information product. The so-called tree crown bound group of trees is used as a new inventory unit of similar size, and they can be combined to produce tree stand information for forest compartments.
The new inventory round will mainly utilize the existing markings as forest compartments, and this data will be supplemented with new laser scanning and aerial photography data from the point of view of changes and possible errors. If necessary, a completely new marking can also be made. In addition, habitat information is retrieved from the existing data for the figures, and forest management and felling proposals are prepared in accordance with the recommendations. Forest resource information by forest compartments is usually published in the second spring of the inventory.
The Finnish Forest Centre’s nature information comprises data on statutory natural sites and non-statutory natural sites.
Statutory sites are nature destinations as defined in the Forest Act, the Nature Conservation Act, and the Kemera Act. Information on statutory sites is constantly maintained and it is important material for the Finnish Forest Centre’s law enforcement task.
Other nature information consists of data on other valuable habitats, retention trees, dead wood and sites that reflect the potential natural values. In addition, other nature information includes broader spatial data sets the task of which is to describe natural phenomena or features that may affect forest use.
New sites are inspected during field work trips
In connection with the inspection activities of the Finnish Forest Centre related to law enforcement tasks and the preparation of environmental subsidies agreements, information is produced on new habitats of special importance defined in the Forest Act. In connection with the inspection, new nature sites detected in the terrain can be inventoried or the data on the areas previously identified as potential nature sites can be checked by spatial data analysis.
After fellings, the Finnish Forest Centre carries out inspections in the terrain, in which case retention trees and dead trees are measured, the implementation of water protection and the consideration of nature sites are assessed in the inspected area.
The collected data is stored as forest and nature information.
Nature information related to the restoration of forest or aquatic environment is also generated in active nature management projects and in the processes implemented by other operators in the forest sector. For example, the preparation of environmental support agreements is also carried out by other forest sector operators, who submit forest and nature information related to environmental support to the Finnish Forest Centre.
New nature sites can be found by combining materials
Remote sensing and combining different spatial data sets can be used to produce information about possible new natural sites. The sites identified as potential will be assessed during a field work trip in connection with other activities and it will be determined whether this is, for example, a habitat of special importance under the Forest Act. Whenever information is generated that has legal implications for a site, the site is inspected in terrain.
The quality of nature information produced by others is always assessed.
The Finnish Forest Centre also receives nature information on forest habitats from external parties. Spatial data are primarily used to assess the quality of information. The site is inspected in the terrain if the inspection cannot be performed reliably with the help of available spatial data or if section 10 of the Forest Act may restrict the handling of the site. Information on endangered species in accordance with the Nature Conservation Act must be submitted to the regional ELY Centre.
Among other things, the information is obtained from:
- forest owners
- forest operators
- nature enthusiasts
- nature organizations
Other sources of information
The Finnish Forest Centre also utilizes the following materials as part of the production and updating of forest and nature information:
- Nature conservation and wilderness areas (Finnish Environment Institute)
- Decisions concerning habitats (Finnish Environment Institute)
- Supplementary proposal for swamp protection. Southern Finland and the implemented sites of the state (Finnish Environment Institute)
- Natura 2000 sites (Finnish Environment Institute)
- Nature Conservation Programme areas (Finnish Environment Institute)
- Groundwater basins (Finnish Environment Institute)
- Species Information System (Finnish Environment Institute / Species Information Centre)
- Land use plans (Finnish Environment Institute)
- Hawk's nests (Species Information Centre)
- Large birds of prey (Species Information Centre)
- Antiquities (National Board of Antiquities)
- Property boundaries (National Land Survey of Finland)