Surveying of parks for tree inventories

Terrestrial Laser Scanning is a method of high-precision collection of spatial information about trees and green spaces using stationary laser scanners installed at ground level. During scanning, the device captures millions of points, forming a three-dimensional cloud that reflects in detail the structure of trunks, branches and crowns.

This method is particularly effective in the inventory of urban plantations and natural monuments, where a high level of detail is required. However, the limited coverage area and the need to move the equipment make it less convenient for large-scale surveys.

Various models of scanners are used for green space inventory by terrestrial laser scanning. Among the most popular are:

• Leica: BLK360, RTC360
• Trimble: X9, X12, SX12
• FARO: Focus

Mobile Laser Scanning is a 3D data collection method where a scanner is mounted on a moving platform, such as a vehicle, ATV or operator's hand or backpack.

One of the key breakthroughs in mobile imaging has been the use of SLAM (Simultaneous Localization and Mapping) technology, which allows the scanner to simultaneously map its surroundings and determine its location without the need for a GPS signal. This is especially important for green space inventory in dense urban areas, parks and forests where satellite navigation signals may be unstable or unavailable. SLAM scanners provide high-speed operation, make it easy to avoid obstacles and collect data in real time, creating accurate 3D models of trees and the environment even in complex areas.

ALS (Airborne Laser Scanning) is a remote sensing method in which lidar is mounted on an airborne platform: an airplane, helicopter or drone. During flight, the laser beam repeatedly scans the surface of the earth, forming a highly accurate three-dimensional model of the terrain and objects, including trees and greenery.

One of the key advantages of ALS is its ability to collect data over large areas in a short period of time, as well as its ability to penetrate tree crowns, creating detailed models of both the upper tier and the undergrowth structure. This technology is widely used for forest inventory, monitoring forest resources, estimating biomass and analyzing vegetation changes.

The diameter of the tree trunk is measured at a standard height of 1.3 meters from ground level, which corresponds to the generally accepted international practice (DBH - diameter at breast height). A special tool is used for measuring - a measuring tape or a large caliper (dendrometer).

When using laser scanning, the diameter of the tree trunk is determined by a point cloud in special software. At a height of 1.3 meters from the ground, a horizontal cut is made in the cloud. The trunk diameter is then measured as the distance between opposite sides of the tree crown.

This approach allows to measure the diameter with high accuracy even for trees with irregular trunk shape. If the trunk is deformed, the average diameter is recorded or several measurements are taken in different directions.

A tree inventory report is a tabular document that systematizes all the data collected during fieldwork about each tree, shrub or group of plantations in a certain area.

The structure of the report may include columns such as:

• No. - serial number of the object
• Species name - name of a tree
• Breed - deciduous or coniferous plant, ornamental form, variety
• Age group - young, middle-aged, mature, old-aged (can be assessed by methods, e.g. trunk diameter)
• Trunk diameter - at 1.3 m (DBH standard - diameter at breast height)
• Height - total height of the plant.
• Crown - size in meters (crown width) and shape (spherical, oval, etc.)
• Coordinates - latitude and longitude of the object for binding on the map
• and other