Fakopp DynaTree User manual

Manual for the
DynaTree dynamic root evaluation system
2018.
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Table of Contents
Introduction......................................................................................................................................2
The pulling test................................................................................................................................3
The DynaTree dynamic root evaluation system..............................................................................4
How does DynaTree wor ?.............................................................................................................5
Some considerations concerning the measurement.........................................................................7
The distance between the measured tree and the anemometer...................................................7
Wind velocity..............................................................................................................................7
Statistical approach.....................................................................................................................7
Multiple measurements...............................................................................................................8
Advantages and disadvantages....................................................................................................8
System components.........................................................................................................................9
Anemometer................................................................................................................................9
Dual axis inclinometer................................................................................................................9
Extensiometer............................................................................................................................10
DynaTree software....................................................................................................................11
Operation guide..............................................................................................................................12
Inclinometer setup.....................................................................................................................12
Anemometer setup....................................................................................................................14
Extensiometer setup..................................................................................................................14
Transferring data from the SD card to a different device..........................................................15
Analysis using the DynaTree software......................................................................................39
Transferring data wirelessly on Windows.................................................................................43
Footnotes..............................................................................................................................44
Introduction
The stability of urban trees is a ey question that affects everyone. Diseased and unstable urban
trees pose much ris for everyone, and are a serious liability for municipalities in case of an
accident. Tree stability assessment is therefore of the utmost importance. In the meantime it tends to
be much neglected in many areas.
At present, there is only one accepted method for tree stability assessment. The pulling test, while
well established and accepted, has several drawbac s, both in terms of reliability and ease of use.
Dynamic root stability determination is based on real life wind loads, and is therefore more
appropriate for assessing real life ris s. It is also much simpler to carry out than the traditional
pulling test, with the only drawbac being that it requires windy weather to carry out.
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The pulling test
Figure 1: Schematic of the pulling test.
The pulling test is based on affixing a cable at approximately mid-height on the tree to be evaluated,
and applying a moderate load, while measuring the inclination at the base of the trun . The induced
inclination is very moderate (less than .25 degrees), to ma e sure that the test itself does not damage
or start uprooting the tree. Based on the measured load, it is possible to extrapolate to the
approximate torque required to uproot the tree. The maximum torque that may arise due to adverse
weather conditions can also be calculated based on the crown surface, aerodynamic drag factor and
the maximum wind velocity li ely to occur in the area. The ratio of the two values is the safety
factor (SF) of the given tree. If this value is above 1.5, the tree is declared safe, while a SF below 1
signals high ris . In-between these two values, the safety of the tree is considered uncertain.
The advantage of the pulling test is that it is a fairly straightforward, well-researched and
established method. On the other hand, the applied static load approximates the real life situation,
where trees are subjected to dynamic loading, rather poorly. It is also quite cumbersome; requires
heavy equipment (high capacity cable and ratchet) and a ladder to be carried to the test site, lengthy
preparation and physical exertion during testing. The pulling cable has to be fastened to some well-
secured object on the ground (li e another tree trun or stump) that may or may not be readily
available.
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The DynaTree dynamic root evaluation system
It would be much simpler to use the loads that arise from the actual wind rather than a loaded cable,
to assess the tree’s safety in a high wind situation. There are, however, two interrelated problems
that ma es this very complicated:
1. Trees consist of a complicated networ of trun , major, minor branches, twigs and (in the
summer) leafs. This situation is not unli e a multiple pendulum that reacts to loading in a
very unpredictable, erratic manner, when the load is not applied directly to the trun (as is
the case in the pulling test).
2. As a result, there is no direct relationship between the wind load (wind velocity) and the
immediate response of the tree, i.e. no correlation between the load and the inclination of the
trun (see Figure 2).
Figure 2: Two-dimensional time series plot of inclination and wind velocity.
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The behavior of a tree in the wind is highly sensitive to the initial conditions. Small differences in
initial conditions yield widely diverging outcomes for such dynamic systems (a situation popularly
referred to as “the butterfly effect”). It is impossible to predict the behavior of such systems on the
long run. A definite relationship exists between the wind velocity and the inclination of the tree, but
it is a complex relationship, not one of immediate cause and effect. One way to evaluate such
systems is using statistical parameters of the data ta en over longer intervals. There is no immediate
relationship between the wind velocity and the inclination at any given moment, but there is a
relationship between their averages and other statistical parameters observed over a longer interval.
The DynaRoot system ta es advantage of this statistical relationship.
How does DynaTree work
Figure 3: Components of the DynaTree system
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The DynaTree system consists of four components (see Figure 3):
1. Anemometer: an instrument for measuring wind velocity at or near the tree to be evaluated.
The closer to the better, but, depending on wind velocity DynaRoot may provide reliable
data even with measurements ta en several ilometres / miles away. The anemometer
provides wind velocity data of sufficient frequency, Ideally the anemometer should be clear
of buildings or other objects that may obstruct the wind, at a height of at least 10 m.
2. Inclinometer: an instrument affixed to the root collar that measures the inclination of the
trun in two different directions. The instrument provides very accurate inclination data with
sufficient frequency.
3. Extensiometer: an instrument attached to the trun for measuring the micro elongation of the
trun
4. Evaluation software: a PC software for evaluating wind velocity, x and y inclination. The
data, recorded over a period of several hours, are transferred from the anemometer and
inclinometer on memory cards or wirelessly via Wi-Fi. The software brea s the data down
into shorter intervals, and calculates statistic parameters for each interval that are used for
the tree stability evaluation.
The Safety Factor calculation is not unli e the one used for the pulling test, except, in this case,
wind pressure is used instead of force, and statistical parameters used instead of the momentary
wind pressure and inclination values. There is a tangential relationship between the wind pressure
and the inclination of the tree, and the critical wind pressure can be calculated from the curves (see
Figure 4).
Figure 4: Relationship between the wind pressure and the inclination
This critical value is used for calculating the SF, which is interpreted much the same way as the one
calculated from the static pulltest.
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Figure 5: An important condition for DynaRoot to be applicable is a sufficiently large wind speed.
Some considerations concerning the measurement
The distance between the measured tree and the anemometer
The intensity of the wind gusts may be different from location to location, even within a relatively
small area. The relationship between wind intensity and inclination is obviously closer if wind
velocity is measured close to the tree. Nevertheless, fairly accurate correlations can be achieved if
the anemometer is located within 1.5 m (1 mile) of the tree, and meaningful data has been
collected when the distance was as high as 5 m (3 miles), unless wind gusts originate from
localized weather events (li e a tornado). It is, of course, best to set up the anemometer close to the
measured tree, but this may not always be possible due to the terrain constraints. It is also possible
that we want to assess multiple trees, or we want to use data from a nearby weather station (possible
if they can provide at least one wind velocity reading per second). As long as wind data is collected
reasonably close, the evaluation is possible.
Wind velocity
The most important condition for the application of this technique is windy weather. The higher the
wind, the better the accuracy of the measurement. The minimum requirement is a wind speed of at
least 25 m/h ~15 mph (see Figure 5).
Statistical approach
As mentioned before, instead of using momentary wind velocity and inclination data, values are
collected over a longer period, and several minutes’ worth of information is evaluated statistically.
The accuracy of the data (the tightness of the correlation) depends on the time interval (see
Figure6).
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Figure 6: Relationship between averaging time and the resulting correlation coefficient
The time interval may be specified in the software when evaluating. 10 minutes provides the best
results; however, this also means that long measurement periods are required to collect enough data
points. 5 min (default setting) or even 2 min measurement intervals offer more data points without
seriously compromising the accuracy of the measurements, if wind velocity is measured nearby. (If
wind velocity is measured more than 1.5 m or 1 mile away, we recommend long collection periods
and using 20-minute intervals for the statistics.)
Multiple measurements
The efficiency of the DynaRoot system multiples when measuring several trees simultaneously.
This is possible, because – unli e in the case of the pulling test – the operator doesn’t have to
supply the pulling load for each tree. The only thing required is a relatively inexpensive
inclinometer mounted on each tree to be evaluated, while the same anemometer can provide the
wind velocity data for each tree (within a radius of several ms or miles). There is no theoretical
limit to the number of trees to be assessed simultaneously.
Advantages and disadvantages
The DynaRoot system offers inclination measurements under real life wind load conditions, which
is a better approximation of the actual situation that eventually leads to the uprooting of a tree, and
therefore may be a more reliable measurement than the pulling test. It is also easier to set up and
carry out; no need for heavy equipment, ladders and physical exertion during the test. There are
only two disadvantages to this measurement. One is that sufficiently high wind velocities (at least
25 m/h or 15 mph) are required, which may be a problem when urgent results are expected. The
other issue is that the measurement is more time consuming than the traditional pulling test.
However, it does not require constant monitoring – after setup, the system can be left alone for the
several hours required to collect the data. It can also be more efficient then the traditional test when
measuring multiple trees simultaneously. Table 1 compares DynaRoot to the traditional pulling test.
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Issue Pulling test DynaTree
Required equipment Cable, ratchet, load cell, ladder,
inclinometer (approx. 50 g)
Anemometer, inclinometer,
extensiometers (approx. 10 g)
Load Static Realistic
Time required 1-3 hrs / tree 3 hrs / several trees
SF calculation Crown area, drag factor and
critical wind speed required
Only critical wind speed required
Weather conditions Wind speed < 25 m/h Wind speed > 25 m/h
Table 1: Comparison of DynaRoot and the traditional pulling test
System components
Anemometer
• Dual axis ultrasonic wind velocity meter
• Sampling rate: 1 Hz
• Measurement range: 0-150 m/h
• Accuracy: 0.2 m/h
• Integrated GPS
• Data storage capacity: 8 GB (SD card)
• Best location: open field, 10 m height,
undisturbed by buildings or other large
objects
• Completely weather proof
Dual axis inclinometer
• Measurement range ±2 degrees
• Resolution: 0.001 degree
• Temperature compensated
• Sampling rate: 10 Hz
• Integrated GPS
• Data storage capacity: 8 GB (SD card)
• Mounted by a single screw
• Operating voltage and current: 12V, 20 mA
• Completely weather proof, IP65
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Extensiometer
• LVDT extensiometers
• Dimensions: 30x30x270 mm (closed)
• Span: 250 mm
• Sampling rate: 1 Hz
• Resolution 0.3 μm
• Power source 2 pcs. of 9 V batteries
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DynaTree software
• Simple yet efficient software for
determining the safety factor
• Automatic merging of wind
velocity, extension and inclination
data
• Diagram, critical wind pressure,
correlation coefficient and safety
factor calculation
• Runs under MS Windows.
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Operation guide
DynaRoot system should be used on days with at least 25 m/h (15 mph) wind gust velocities.
Setting up the measurement involves mounting the inclinometer(s) on the tree(s) root collar to be
assessed, and erecting the anemometer in the vicinity of the trees.
Inclinometer setup
• attach the mounting plate using a screw to the tree collar (as close to ground level as
possible.)
• use the ball head to level the mounting plate (using the two leveling tubes) and set it in the
horizontal position.
• slide the inclinometer onto the mounting plate, and secure it with the bolt.
• connect the High Precision Inclination Recorder or the High Precision Inclination and
Deformation Recorder. Chec the leds as shown on figure 7.
Figure 7: Indicator leds on the High Precision Inclination Recorder
• connect the wires to the external battery (12 VDC). Ma e sure not to reverse the polarity!
• wait for the OK LED to light up. This may ta e a few minutes depending on the quality of
GPS signal reception.
• when the OK LED is lit, you may press SD START on the control panel located on the side
of the instrument box (see figure 8). Use the provided magnetic stic to operate the buttons.
Once pressed, the OK led starts blin ing. A few minutes later the OK led turns down to be
less noticable.
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Figure 8: Buttons of the control panel
• record data for a suitably long period of time (the longer the better. The minimum is 1 hr, but
3 hrs are recommended.)
• hit STOP on the control panel and wait for the recording to finish. (approx 1-2 s, until the
SD led (3) goes off).
• transfer the data from the SD card to a different device for further processing (see subsection
7.3 for more instructions).
• remove the power cable.
The instructions above should be sufficient to get you started with data acquisition. However, under
some circumstances the above mentioned procedure might partially or completely fail. Fortunately,
the 7 led indicators on the High Precision Inclination (and Deformation) Recorder (see figure 7)
provide us information concerning the operating conditions. Below we give a more detailed
description about how to interpret the combination of signals. At the moment of powering up the
device, all leds are on for the duration of a second. The boot process is the following
• if the BA led turns on, you won't be able to use the instrument for data recording. Replace
the battery with a sufficiently charged one.
• If power supply was found to be appropriate, the process continues with chec ing the GPS
signal. This process ta es at most 3 minutes, but may finish as early as 30 seconds if the
reception is good. There are 3 possible outcomes:
• if the GP led turns off, it means that both time and position was received
successfully.
• if after 3 minutes the GP led is blin ing, it means that time was received but position
was not.
• if after 3 minutes the GP led becomes continuous, it means that neither time nor
position was received. In such cases ma e sure that nothing bloc s the reception of
the satellite signals, disconnect the wires of the battery and restart the boot process
by connecting it again. If after rebooting you don't end up in any of the previous 2
cases (and there won't be other failures during the boot process), you will still be able
to use your device but you have to use an external cloc to note down the time when
the SD START and STOP buttons were pressed and contact us for further assistance.
• if the SE led stays on, then there is a problem with reading out data from the inclinometer
therefore registration won't be possible. Try to reboot by disconnecting then reconnecting to
the battery. If it doesn't help, contact us for further assistance.
• if the SD led stays on, it indicates that the SD card has an error and registration won't be
possible. Replace your SD card with an intact one.
To summarize it, if either the BA, the SD or the SE leds stay on, then you won't be able to use your
device for registration. If the GP led stays on (either continuously or blin ing), you can use your
device but have to note down the time when the measurement was started and stopped manually. If
all the lights goes off except the OK light then it indicates that everything went well and registration
can be started.
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Anemometer setup
Assemble the anemometer tower, attach the anemometer on the top, and erect the tower. Wind
velocity readings are sent to, and data is collected at the instrument box located at the bottom of the
tower. Starting and stopping the data collection, recording and transferring data happens much the
same way as described above at the inclinometer. The instrument box contains the same control
panel (including start and stop buttons) as that of the inclinometer. Do not forget to press “Tara”
button inside the instrument box before raising the anemometer. Cover the sensor by a plastic bag to
stop wind in the sensor area while performing “tara” function. After pressing “tara” please remove
plastic bag.
Warning! Ma e sure that you setup and start the anemometer before the inclinometer(s),
otherwise you won’t be able to evaluate the part of the inclination data recorded before starting the
anemometer!
Extensiometer setup
Mount the first extensiometer on the tree trun . Try to select the wea est region (based on visual
inspection.) Screw in the top (2) and bottom (6) screws without releasing the securing jaws. Then
loosen the thumb screw (4) and slide up the collar (3) to release the jaws (5) and thus allow the
extensiometer to move freely.
Mount the second extensiometer in 90 angle to each other. Both of them should be paralell to the
direction of the trun itself.
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Connect the extensiometer cables to the dual elastometer unit, and connect the unit to the High
Precision Inclination and Deformation Recorder.
Switch on the units, and press “Tara” on the load cell.
Transferring data from the SD card to a different device
During the data acquisition phase, several files with the extensions txt or csv are created on the
SD card of your inclino- or anemometer. The number of csv files created are roughly equal to the
hours of operation in the case of the inclinometer and three times the hours of operation in the case
of the anemometer. The DynaTree evaluation software will automatically now how to interpret the
format of these files so there is no need to do any preliminary conversions. After the data
acquisition phase you need to transfer the data stored on the SD card in the instrument box to your
mobile device or your PC for further analysis. At the moment there are two possible ways to
accomplish this:
1. Opening the instrument box and removing the SD card manually.
2. Putting the instrument into Wi-Fi mode and downloading/deleting data from the SD card via
FTP without opening the case.
The first method should be straightforward and won't be detailed here.
Warning! Always ma e sure that the OK LED on the High Precision Inclination (and
Deformation) Recorder is continuous. If it's blin ing instead, then it indicates that registration and/
or the data saving is still on and it needs to be stopped first by pressing the STOP button on the
instrument. If you remove the SD card while the green OK light is blin ing it may results in data
loss or damage to your card.
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Since this method has the slight disadvantage of having to open the case of the instrument, Fa opp
Enterprise offers a second solution that utilizes wireless communication technology. Transferring
data wirelessly to an external device with a wireless networ interface consists of
1. putting the instrument into WiFi mode,
2. connecting to the wireless networ of the instrument from the external device and
3. downloading data to the external device via FTP protocol.
In order to establish wireless connection to your device, it should be set into Wi-Fi mode by
pressing the WIFI START button.
Warning! If the green indicator light labeled OK on the High Precision Inclination (and
Deformation) Recorder is still blin ing then it indicates that registration/data saving is still on and
it needs to be stopped first by pressing the STOP button prior to activating Wi-Fi mode.
If Wi-Fi mode is successfully activated, then the white indicator light labeled WF on the High
Precision Inclination (and Deformation) Recorder is continuous and the device is ready to accept
connection requests from any sort of devices which has a wireless networ interface (such as a
laptop, a mobile device or even a des top PC). The SSID of the networ to connect to always has
the form of DDAR-XX:XX:XX:XX:XX:XX, where the part of SSID following the hyphen is a
valid MAC address unique to the purchased instrument instance. The connection uses the WPA
security protocol for authentication, for which the passphrase is Ddar-123. In the following we
are going to illustrate this process under Android OS. The steps needs to be ta en are very similar
on other platforms.
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Figure 9: Go to Settings / Wi-Fi to see the available Wi-Fi networ s. Select the networ with SSID
DDAR-XX:XX:XX:XX:XX:XX, where the part after the hyphen is a unique MAC address. In the
concrete example shown on the picture below, it is the sequence 5E:CF:7F:1B:43:52. Evidently, if
you purchased two different HPI recorders, then both will have different SSIDs associated to them.
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Figure: Enter the passphrase Ddar-123.
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Figure 11: The status message 'Obtaining IP address...' should appear below the networ name.
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Figure 12: When the connection is successful, then the previous message changes to 'Connected'.
Once the connection to the WiFi networ of the instrument is established, we are ready to
transfer/delete files using a suitable FTP client. We are going to demonstrate this process on
Android platform using the FTP client program named Turbo FTP 1. The required steps are as
follows.
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