Trees are an essential part of our cities. They provide shade, cool urban spaces, support biodiversity and contribute to people’s well-being. Yet, when a tree loses stability, pedestrians, vehicles and nearby infrastructure security are put at risk. Understanding how trees respond to external forces is therefore an important part of urban tree management.
Traditionally, assessing tree stability relies on visual inspections and, when necessary, specialised instrumental tests. These methods provide valuable information, but some require costly equipment and experienced professionals. Could smaller, more affordable sensors help make these assessments more accessible?
A recent study published in Forests explores this question by evaluating a low-cost inclinometer based on Micro-Electro-Mechanical Systems (MEMS). The researchers investigated whether the sensor could measure small changes in tree inclination reliably, first under controlled laboratory conditions and then during field tests on a standing tree.
The results offer promising evidence that this technology could complement existing tools for assessing tree stability.
Why Does Tree Stability Matter?
A tree’s stability depends on the interaction between several elements: its trunk, branches, root system and the soil surrounding the roots. Wind and other external forces can cause the trunk to bend and the root plate to rotate. How a tree responds depends on its structure, its condition and the characteristics of the ground in which it grows.
Visual inspections are an important first step in identifying potential problems, such as cracks, decay, damaged roots or changes in the tree’s structure. However, visible signs do not always provide a complete picture of how a tree will respond to an applied force.
Instrumental tests can provide additional information. During a static pulling test, for example, a controlled force is applied to a tree using a cable and winch while instruments record its mechanical response. Measurements of inclination, combined with other relevant information, can help professionals investigate how the tree and its root–soil system respond to loading.
These tests require appropriate equipment, trained operators and careful interpretation. Developing more affordable measurement technologies could help broaden access to instrumental assessments, provided that their accuracy and limitations are properly understood.
What Is a MEMS Inclinometer?
These technologies combine very small mechanical structures and electronic components on a chip. They are widely used in devices such as smartphones, where they help detect movement, orientation and changes in acceleration. An inclinometer uses measurements of orientation relative to gravity to estimate an object’s tilt. In tree stability research, this principle can be used to record small changes in trunk inclination when external forces are applied. The sensor performance was compared with theoretical inclination values in the laboratory and with a professional high-precision inclinometer during field tests.
The key question was not simply whether the sensor could detect movement. It was whether it could measure small changes consistently enough to be useful in a demanding application such as tree stability assessment.
From the Laboratory to a Real Tree
The researchers tested the sensor in two stages. First, in the laboratory, they attached it to a steel beam and tilted it by known amounts to check whether its measurements matched the expected angles. They also explored how the time spent collecting measurements affected accuracy. Averaging readings over longer periods helps reduce small, random variations, although it takes more time. Under laboratory conditions, averaging measurements over 120 seconds reduced the absolute error to approximately 0.005–0.015 degrees.
Next, they tested the sensor on a real tree, placing it alongside a professional high-precision inclinometer. During controlled pulling tests, both instruments recorded how the trunk tilted at two different heights. Rather than comparing absolute angles, the researchers focused on whether both devices detected changes in inclination in the same way. The results were promising: both instruments detected almost identical changes in the tree’s inclination. Even when the trunk moved by very small amounts, the low-cost sensor was able to follow its movements closely, producing readings that differed only slightly from those of the professional instrument. This suggests that a more affordable device could provide useful measurements of how a tree responds to applied forces. The results suggest that MEMS technology could offer an affordable way to measure changes in tree inclination during controlled stability tests, although further research is needed to assess its performance under a wider range of field conditions.
What Could This Mean for Urban Tree Management?
The potential value of a low-cost inclinometer lies in making useful measurements easier to obtain. A wireless, battery-powered sensor with relatively simple data processing could offer a practical complement to more expensive professional equipment. For example, such sensors could potentially support repeated or scheduled measurements during controlled pulling tests. Measurements taken at different heights along a trunk could also help researchers investigate how deformation varies along the stem.
In the longer term, more accessible sensing technologies could contribute to data-driven approaches to urban forestry. When combined with professional inspections, information about tree condition, local soil characteristics and environmental conditions, instrumental measurements may help managers make better-informed decisions about which trees require closer examination.
However, a measurement of inclination is not the same as a prediction of tree failure. A sensor can record how a trunk responds to an applied force, but that information alone cannot establish whether a tree is safe or unsafe. Assessing stability requires the interpretation of measurements within an appropriate technical framework and consideration of the wider tree–soil system.
What Still Needs to Be Tested?
The study provides a preliminary assessment, and several questions remain open.
The tests were limited to specific conditions and measured changes in the tree’s inclination in one direction. More research is needed before the sensor can reliably assess overall tree stability or determine whether a tree is at risk of falling. Further research is needed to assess performance across different tree species, sizes, soil conditions and environments. Long-term operation introduces additional challenges, including temperature sensitivity, sensor drift and ageing. These factors must be investigated before the technology can be relied upon for extended monitoring.
Finally, low-cost sensors should be evaluated not only in terms of price, but also in terms of reliability, maintenance requirements, data quality and how effectively their measurements support professional decisions.
Towards More Accessible Tree Stability Assessment
The study by Incollu and colleagues demonstrates how a relatively small sensor can provide useful measurements of tree inclination when appropriately calibrated and used under defined conditions. Its close agreement with a professional instrument during the reported field tests is an encouraging step towards more accessible measurement technologies. The next challenge is to establish how robustly these results translate to different trees and real-world operating conditions.
For TREESURE, research of this kind illustrates an important principle: improving tree safety is not simply a matter of collecting more data, but of developing reliable tools that help professionals understand risk and make informed decisions. Low-cost sensing technologies could become part of that effort, complementing established assessment methods while further validation continues.
Read the original scientific study: Preliminary Metrological Characterization of Low-Cost MEMS Inclinometer for Tree Stability Assessment: From Laboratory to Field.