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Inch Calculator and Personal Laser Scanners (PLSs), thanks to a reduction
in sensor size.
MLSs do not require stationary positioning during data
acquisition, enabling integration with aerial vehicles or processor

harvesters, while PLSs can be handheld or worn in a backpack.
Both allow faster data acquisition over larger areas within
the same amount of time compared to static TLSs but have
of damage was similar among assessment methods. lower accuracy (centimetre-level) and increased acquisition
Computer vision and deep learning techniques were also noise. Nonetheless, comparisons between mobile and static
employed by Niknejad et al. on stereo images to determine instruments have reported similar results.
stem diameter as well as branch diameter and angle in More recently, image-based solutions have gained more
loblolly pine trees. and more attention due to their affordability, portability, and
Comparison with manual measurements indicated sufficient easy-to-use devices for data acquisition (typically a camera),

accuracy in stem diameter measurement, while branch coupled with the availability of automated, user-friendly software
assessment was affected by the small size of objects to be for data processing and rapid algorithm advancements for
detected, resulting in values only suitable for determining size data computing.
classes (small, medium, and large) due to insufficient accuracy. Another advantage of photogrammetry is the capture
of realistic images, which facilitate rapid, easy, and intuitive
Future Directions validation of the collected information.
Initially focused on measuring inventory variables like tree However, being a passive sensing technique, photogrammetry

dimensions and biomass, lasers or image-based techniques is highly influenced by variations in light and atmospheric
have expanded to include parameters linked to wood quality, conditions, which impact image quality. Additionally, the success
such as stem form and branch characteristics. of 3D reconstruction relies on factors like picture angle and
Studies have shown these methods to be capable of overlap. Therefore, for all these reasons, the development of an
providing versatile, quantitative measurements. However, acquisition protocol could help the user optimise the results.
despite promising results, widespread adoption is hindered While data acquisition in photogrammetry is relatively
by the need to balance the advantages and disadvantages fast thanks also to easy mobility in field measurements (like
of each technique. for PLSs), its accuracy is lower than laser-based techniques
Currently, static TLSs serve as a reference for point but still adequate for operational requirements. Though direct

cloud-based inventory measurements. One advantage is its comparisons between photogrammetry and TLSs remain
capability to quickly and automatically detect tree attributes limited, initial results suggest good agreement between the
with millimetre-level detail. two techniques.
However, most sensor devices are very expensive, and Finally, it is worth mentioning the research aimed at
the technique demands substantial computing power for data combining the two technologies. Since both have strengths
processing along with expert personnel to extract numerical and weaknesses, their combination can lead to more effective
variables. results compared to using them individually.

To mitigate some of these drawbacks, low-cost TLSs have The fusion of laser scanning with optical imaging has
entered the market, alongside Mobile Laser Scanners (MLSs) been applied in various fields, as reviewed by Zhang and