PiCUS Tree Motion Sensor 3

The Wind-Reaction-Measurement with PiCUS TMS is used for in depth tree inspections to obtain information about a tree’s stability, defined by its root anchoring force in the ground.


PiCUS TMS 3 – consistently innovative

Bluetooth-communication – control via mobile phone
New inclination measurement – quick and simple installation
Small and stealthy – Even you will have trouble finding it!

Wind-Reaction-Measurement – the method

The Wind-Reaction-Measurement records the dynamic sway motion of a tree in naturally occurring wind, by measuring the root plate tilt.

The reaction of a tree is measured directly, including all environmental influences.
These include tree specific parameters (size, form of the crown etc.), wind strength and wind exposition (buildings and other trees in the vicinity).

In contrast to this the tree pulling test (Wessolly & Erb, 1998), an established method for assessing root defects, uses an artificial wind replacement load. However, an estimate for the correlation between actually occurring natural wind and the artificial wind replacement load is rather difficult because of the previously mentioned environmental influences.


Typical applications for Wind-Reaction-Measurements

Confirmation of stability
If trees only show a small root plate tilt, even in strong wind gusts, one can assume a stable root system.

Identification of trees with root anchorage problems
After measuring tree groups comparing the results can identify trees with conspicuously large root plate tilt.

Combination with static tree pulling test (TreeQinetic) with regards to stability
If a tree with increased tilt angles has been identified, it is often meaningful to follow up with a static pulling test to measure the trees reaction to a known force.

Addition to sonic tomography (PiCUS Sonic Tomograph) and resistance tomography (TreeTronic3)
Trees with large defects in the lower stem area (with assumed root defects) should additionally have their stability tested in natural wind

Surveillance of trees near construction
Sustained changes in a tree’s tilt angle during groundworks (e.g. placing of sheet pile walls) can be detected with the PiCUS TMS.

Long term monitoring of trees
Trees suspected of having root anchorage problems can be inspected in regular intervals to check whether:

  • The root plate tilt in wind decreases (tree grows new and stronger roots)
  • The root plate tilt in wind increases (roots are dying off or get damaged otherwise)
  • The reaction remains constant

Technical data of the PiCUS TMS Systems

Parameter PiCUS TMS 3 PiCUS TMS
General characteristics    
colour  grey  black
weight  73 g 270 g
dimensions  61 mm x 41 mm x 20 mm 100 mm x 80 mm x 75 mm
protection  Completely sealed against water and dust  Protected against rain and dust 
min. livetime 5 years  5 years
Accuracy tilt measurement  0,03 ° 0,03 °
Measurement interval  0,05 s (20 Hz) 0,05 s (20 Hz)
Type of tilt measurement  3D measurement 2D measurement
Sensor orientation  arbitrary  horizontal 
Accuracy temperature measurement  1 °C 1 °C
Temperature range  -20 – +50 °C -20 – +50 °C
Battery capacity and runtime 250 mAh; > 14 days 2900 mAh; > 20 days
Charging  wireless Micro USB cable 
Charge duration  approx. 2 h  approx. 6 h
recommended charging temperature  5 – 35 °C 5 – 35 °C
Memory type    MicroSD memory card 
Memory size  256 MB Up to 32 GB
Memory runtime  20 days > 130 days (1 GB memory card) 
Standby- and measuring mode  Bluetooth Low Energy 4.0 Micro USB cable 
Data download  Bluetooth Classic 2.1 MicroSD card reader 
TMS power on Magnetic key  Electrical switch 
Outdoor-handling BLE-capable mobile phone (Android, iOS)
+ TMS 3 App
Electrical switch 
Data download and analysis  PC with Bluetooth Classic
+ TMS 3 Control software (direct sensor interaction)
MicroSD card reader
+ TMS PC software 
PiCUS TMS-case    
Power supply  230 V AC, 50 Hz (adaptor)  230 V AC, 50 Hz (adaptor) 
Number of TMS-chargers  10 (wireless charge bays)  10 (MicroUSB cable charger) 
Maximum number of TMS  20 20
weight, filled (screws, cables, 10 TMS)  5,5 kg 11 kg
Maße  48 cm x 35 cm x 15 cm 60 cm x 45 cm x 17 cm

Important software features:

TMS PC-Software

  • Visualisation of raw data (tilt angle and direction)
  • functions for identifying and analysing of tilt events
  • direct comparison of tilt values from different PiCUS TMS (typically base and control sensor on the same tree)
  • Automated data analysis and Wind Tipping Curve calculation

PiCUS TMS 3 only

  • App for PiCUS TMS 3 control:
    • Status display
    • Input of tree data in preparation of a measurement
    • Live-measurement mode
  • Extension of the PC program:
    • Automated read out of PiCUS TMS 3 measurement data
    • Automated structuring of all tilt and wind speed data by project (data base creation)
    • Direct comparison of all PiCUS TMS 3 measured tilt values (on the same tree)
    • Direct comparison of Wind Tipping Curves from different trees
    • Automated read in and processing of wind measurement data (recorded with TMS Wind Measurement System)

Application of Tree Motion Sensors

Wind causes tilting of the root plate and bending in the tree’s trunk. 
The PiCUS TMS are inclinometer which dynamically log changes in root plate tilt over hours, days or even weeks.


  • Wind gust speeds > 45 km/h

Implementation of measurements:

  • Mount sensors before a wind event, end measurement after the wind calmed down (minimum measurement duration 2h)
  • 2 PiCUS TMS per tree:
    base sensor on the trunk base – direct measurement of root plate tilt
    control Sensor in 2-3m height – for filtering out ambient noise sources (e.g. road traffic) and for identifying actual wind events
  • Comfortable analysis in your office, minimized on site time

If the base sensor shows tilt while the control sensor doesn’t, it is ambient noise.
On an actual wind event the value of the control sensor has to be higher than the base sensors, because the upper sensor not only measures the root plate tilt but also the superimposed bending of the tree trunk.

Analysis and interpretation of measurement data

The included PC software creates diagrams showing the relationship between wind speed and root plate tilt - the Wind Tipping Curve. Wind speed can be measured either on site (TMS Wind Measurement System) or it can be read and added manually from external sources (eg.windfinder.com). 

The ability to extrapolate tilt, for wind gust speeds 10 to 20 km/h above the ones measured, allows predicting the tree’s performance at said wind speeds.

Below are wind tipping curves from three Douglas fir measured during hurricane Xaver (wind speeds of up to 93 km/h, measured by a weather station approx. 9 km away).


The red curve is from a Douglas fir which has both a large defect in the trunk base and strong root swellings (see PiCUS sonic tomogram). The other two curves are from neighbouring trees without defects in the trunk base. It can be seen that the Douglas fir with defect shows even less root plate tilt than the reference trees.

The Douglas fir reacted to the internal defect by growing stronger roots.

Application examples

  • Comparative analysis of grouped trees
    All trees in an alley of acer were fitted with PiCUS TMS. This allows fast and simultaneous testing of all trees with little effort. The comparing analysis identified trees that show unusually high tilt values, compared to others in the same group. 

    In a direct comparison of the Wind Tipping Curves it is clearly shown that acer 5 has a significantly higher tilt compared to the other four. Therefore, this tree should be inspected much more thoroughly (with other commonly used methods)

  • Single Tree analysis
    The tomogram shows a large defect in the trunk base (tilia with Kretzschmaria deusta). 

    Point 1 – Root plate tilt in wind speeds > 90 km/h already 0,7° (defoliated)
    Point 2 – tilt extrapolation for a wind speed of 110 km/h: 1,4°

    The Kretzschmaria deusta already affects the root stability of the tilia. According to the Generalized Wind Tipping Curve (by Sinn / Wessolly / Erb 1998) a tree pulled to a tilt of 2-4° will fall down without further increasing the applied force (uprooting force). Therefore, the tilia will not yet tip in wind speeds of 110 km/h.

Anemometer (optional)

The TMS Anemometer is a wind speed and wind direction data display and recorder. It consists of an anemometer for the wind speed, a wind direction sensor and a data logger. In addition, a 10 m mast is available on which this equipment can be mounted.

The advantage of using the anemometer is that the wind data is collected in the immediate vicinity and thus can achieve particularly good correlations of wind and inclination data. Furthermore, the recorded wind data with high measuring frequency is available. These advantages are particularly noticeable where the network of publicly accessible measuring station is thin or geographic peculiarities permit a limited transfer of regional wind data to the subject trees.

A unique feature of the anemometer is the direct data import into the TMS 3 Control software. The data logger uses a file format that can be used with further intermediate steps with the data of the PiCUS TMS 3 sensors. While foreign file formats cause additional work and are prone to errors because they have to be adjusted by hand, the direct connection of the data logger can be opened with just a few clicks and the data transfer can be started.

Data logger - technical data  
supply voltage 3,6 V via built-in LiPo battery
current consumption < 1 mA
interface USB 2.0 for communication with PC
temperature range -10 °C ... 60 °C
dimensions (LxWxH) 110 x 60 x 35 mm
current consumption during charging 350 mA
charging time ca. 4 h
running time ca. 30 days
Anemometer - technical data  
supply voltage 5 V DC
current consumption < 0,01 mA (5 V power supply, without external load)
signal output

voltage pulse input near the supply

(16 pulses/revolution, loadable max. 5 mA)

measuring range Anlauf < 0,3 m/s, bis 50 m/s
temperature range -20 °C ... 70 °C
dimensions 135 x 135 mm
Wind direction sensor - technical data  
electricl outlet voltage 0 ... 5 V DC
suplly current < 20 mA
measuring principle Hall effect absolute value encoder
measuring range run-up 0,2 m/s, 0 ... 360°
temperature range -25 °C ... 80 °C

height 140 mm

turning radius of the flag 150 mm

resolution 1024 (10 Bit) / 4096 (12 Bit)
update rate 1,0 ms
output load > 10 kΩ

Mobile Apps

To work with the new TMS 3 sensors it is necessary to download the associated App from the app store. Please click on dedicated store button or scan QR Code below.