Overview of Changes in Forest Heights web map

Changes in forest heights using the lidar sensor of the Estonian Land and Spatial Development Board

Since 2008, the Estonian Land and Spatial Development Board has carried out regular survey flights to collect orthophotos and lidar data. Estonia has been surveyed 3 times in almost 10 years, which creates a good basis for identifying changes. One such example is the detection of anthropogenic and natural changes in the height of vegetation cover.

The Estonian Land and Spatial Development Board's lidar device (aerial laser scanner) collects data consisting of billions of survey points, which are collectively called a point cloud (also point swarm). Each such survey point has location and elevation information, which can be used, for example, in calculating a vegetation height model. The vegetation height model characterizes the height of vegetation above the ground.

If vegetation height models calculated from lidar data flown at different times are compared, places where vegetation height has changed can be found. The vegetation height change layer published by the Estonian Land and Spatial Planning Board has adopted the following criteria: the vegetation height must have decreased by more than 5 meters between two lidar survey flights and the minimum area size displayed must be at least 2500 m2. When calculating this layer, only the decrease in vegetation height was considered, not the increase.

If you click on the area displayed on the map layer, an information window will appear, showing the area size in hectares and the dates between which the change was detected.

In the example given, the date of the first survey refers to the date of an earlier flight in 2017 (April 6, 2017) and the date of the second survey refers to the date of a later flight in 2019 (June 5, 2019). Thus, the change has occurred between these two dates, approximately 2 years. In the example given, the vegetation cover in the height model calculated based on lidar data collected during the 2017 flight was at least 5 meters higher than the vegetation cover in the height model calculated based on lidar data collected during the 2019 flight. Since 2016, the Land and Space Administration has been using a new aerial camera (Leica ADS100-SH100), which allows it to fly higher and cover a larger area at once, but to take an image of equivalent quality as before. Since aerial imaging and laser scanning are performed simultaneously, the lidar data in 2016 had a lower survey density and were not suitable for calculating the vegetation cover height model. Therefore, the identification of changes in vegetation height based on the 2016 data has not been done.

The Land and Spatial Planning Board would like to emphasize that this is not official logging statistics, but an informative data layer calculated as a result of automatic processing, which contains errors and inaccuracies. The inaccuracies and errors are due to the lidar data collected under different conditions and the specific nature of the data processing (data classification, filtering and smoothing).

To get information about an area, click on the area in the application. An information window will appear, where you need to select "Forest changes" and click on it. A layer will open, showing the area size in hectares, the times of the first and second survey flights.

To get a better overview of which area a map layer covers, the cartograms below will help. For example, the 2012 map layer covers Western Estonia and the entire coastal area of ​​mainland Estonia, and the 2017 spring flight area covers Saaremaa, Pärnu and Viljandi counties. Therefore, there are places where the map layers overlap and the areas displayed in the application also overlap.

Additional information: Sulev Õitspuu, sulev.oitspuu@maaruum.ee

Estonian Land and Spatial Development Board, Department of Geoinformatics, Head of Bureau of Geoinfosystems