Researchers from the Center of Excellent Research EVA4.0 (SP 5 and 6) of the FFWS of the CZU in Prague researched the possibilities of forest stands scanning using new and generally available technologies such as is an iPad or even an iPhone. The results suggest that practical results can already be achieved in this area.
The introduction of new laser measuring and scanning technologies in the last 20 years has meant a major shift in various areas from archelogy to forest inventory. The scientific team of Dr. Mokroš from the Centre for Excellent Research EVA4.0 at the Czech University of Life Sciences in Prague, together with colleagues from Finland, Poland and Slovakia, therefore organized experimental measurements with new and available technologies.
"Recently, a relatively dense network of 3D data can be generated not only by conventional ground-based laser scanning, but also with the help of smaller devices carried in the hand or backpack. The necessary data can also be obtained with the help of photogrammetry," says Martin Mokroš.
One of the devices that can be used for 3D scanning is also an iPad or iPhone with a special sensor (iPad version Pro, iPhone version Pro and Pro Max). CULS researchers also used their own prototype of a multicam system, a relatively common hand-held scanner and a traditional ground-based laser scanning device (TLS).
Our researchers tested the capabilities of these facilities in eight research areas. "In our pilot experiment, we have focused on the facility's ability to detect individual trees in research areas. From all the technologies used, we were able to generate 3D point clouds, which we then processed using an algorithm developed by us. The results show that the iPad is second best (after traditional TLS technology) in detection of forest cover with detecting rate of 77.24% of trees in the research areas. The manual scan achieved a result of 67.91% and the prototype of the multicamera 64.18%. The results of all devices improved even more when the limit of the enumerated thickness of the tree was moved up to 20 cm. The time during that one research area was scanned is also interesting. For PLS it was 40 minutes. The iPad did the same job in 15 minutes and the handheld scanner in just 10 minutes. With a multi-camera system using photogrammetry, it was then possible to achieve a time of 8 minutes," says Martin Mokroš.
The measurement results show that each device has its strengths and weaknesses. Traditional PLS was able to capture over 90% of defined trees. However, the measurement time is relatively long and the device is expensive. The prototype of the multi-camera system proved to be very fast, but the least accurate in comparison. "Only the iPad is a solution that provides the operator with a point cloud in real time. This advantage is highly usable for forestry practice, where the forester can check the results directly in the field and in case of discrepancy correct the error in an instant. This is not possible with other technologies used, as the data must be processed in the office. On the other hand, data collection must be carried out very carefully so the same areas of the forest are not scanned twice," adds scientist Martin Mokroš.
At present, EVA scientists are developing their research of commonly used technologies in forestry under the leadership of doc. Peter Surový. The mobile application that uses an iPhone or iPad to measure basic forestry parameters (iscanforest.fld.czu.cz) was introduced. From our results and mentioned facts, it is possible to predict, that new forest inventory methods will soon be available to a wide range of forestry and forestry researchers.
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