VTOL drone WingQuad 3 used for improving efficiency in forest inventories
What is a forest inventory?
A forest inventory is a systematic compilation of forestall information, to evaluate and analyze several factors and characteristics of the forest. Among the reasons for executing a forest inventory, is to provide complete information about the state and dynamics of the forest, accomplish a strategic and management plan, estimate the value and possible uses of the wood, determine the risk of fire and environmental variations, determine environmental values of the forest such as carbon pools, biodiversity, among others.
The main tasks that must be done in a forest inventory, is to measure and take note of the type of species found, the chest diameter height, the total height of the trees, health condition, among others. With this information, it can be estimated the number of trees per hectare, the basal area, the volume of trees in a certain area, and the value of the wood.
To execute a forest inventory, manual methods have been generally used. Among the instruments used for the purpose are the following: Biltmore stick, diameter tape, tree caliper, relascope, clinometer, cruising rode, increment borer, among others. While it is true that these methods can be very accurate and precise, when it comes to big extensions, those methods may not be the more effective nor efficient ones.
Graphic 1. Live photography of the flight of the autonomous vehicle Wingquad 3
Therefore, disruptive technology has been introduced to achieve and cover greater forest inventories in a more efficient way. Among the innovative technology that has been adapted for the inventories are UAV´s (Autonomous vehicles-drones). For making our forest inventories, it has been used several types of drones, but the most efficient for the task is the autonomous vehicle Wingquad 3. This drone is a VTOL model, meaning Vertical Take of and Landing. It has flight autonomy of 60 minutes and can cover up to 500 hectares per flight. Therefore, it has been efficient when the forest inventories cover hundreds to thousands of hectares.
The forest inventories that we have realized with the Wingquad 3 consist in aerial photo acquisition of the whole area for its subsequent interpretation and analysis, to obtain the dasymetric data of the species that are identified by remote sensing. The methodology of gathering information allows covering all the extension of the study in a geo-referenced manner, including those areas that can be omitted in fieldwork.
The following are the procedures that were used to realize the forest inventories with the autonomous vehicle Wingquad 3. First of all, it was developed the flight planning of the drone, taking into account the shape of the terrain, the heights of relevant elements, to organize and plan the flights. Then, it was selected and located the control points, depending on the scale and the purpose of the inventory. Afterward, by using the Wingquad 3, it was taken the aerial photography acquisition. With the data obtained from the flight, it was processed the aerial photography, getting relevant results such as the digital terrain and surface models (MDT and MDS).
Graphic 2. Digital surface model
Graphic 3. Digital terrain model and contour lines
With this information, it could be made the plant cover classification and the extraction of areas of interest.
Graphic 3. Selected areas of interest
After, it was realized the accounting for species, through geometry segmentation techniques, optimizing the tolerance threshold. Then, it was applied algebra of maps between de MDT and MDS to obtain heights of species. Through the generation of algorithms, it could be determined the dasymetric data of trees (Baseline DAP, number of logs, commercial heights). These results were calibrated with field data, and finally, the result tables were generated.
The following is a table of results that were obtained from one of the forest inventories realized with the autonomous vehicle Wingquad 3. With the procedure previously described, there were obtained the data from the table. The main information displayed in the table is circumference of the trees, total and commercial altitude of the trees, the commercial volume of the trees, and finally the monetary value that could be obtained from the wood. All the information presented has been obtained with a combination of fieldwork and the acquisition of photos from the drone.
Table 1: LAS-ECOSERV Forest Inventory, 2018
Autonomous vehicles are an excellent option when it comes to executing forest inventories, due to their efficiency and precision of the results obtained. With Wingquad 3, it has been possible to achieve several environmental projects such as forest inventories. The main advantages of it are the flight autonomy, 60 minutes approximately and the capacity of carrying any sensor needed for the inventory. Therefore, by combining the flight and capture of data with the autonomous vehicle Wingquad 3, and by doing the precise fieldwork, we have been able to execute several forest inventories, achieving precise results in the more efficient way possible.