SUCCESS STORYUAVUAV Flight Analysis for Wind Measurement
MASC is a small UAV developed for atmospheric boundary layer research. The Ellipse-N has been chosen
to record the UAV position, ground speed, and attitude angles. By taking into account the airflow, windspeed and direction can be accurately calculated.

The Multi-Purpose Airborne Sensor Carrier (MASC) is a small unmanned aerial
vehicle (UAV) developed for atmospheric boundary layer research. It is
designed and operated by the Environmental Physics group at the Eberhard
Karls Universität Tübingen, Germany.

CLIENT

Environmental Physics Group at theEberhard Karls Universität Tübingen,Germany
APPLICATIONWind energy plant site evaluation
using a UAVPRODUCT

Ellipse-N, Miniature Attitude & Heading Reference System (AHRS) withintegrated GNSS receiver
PROJECTUAV position, ground speed, andattitude angles recording

The typical payload for this UAV is ameteorological measurement system,
designed to calculate turbulent fluxes.
Compared to terrestrial systems or aircrafts, the MASC UAV is a cost-effective
and valuable tool for researches suchas wind energy plant site evaluation incomplex terrain.

“IN-FLIGHT” WIND SPEEDCOMPUTATION
In-flight wind computation might betricky because airspeed and incident

angles, measured by the embedded
airflow probe, need to be compensatedby the actual UAV behavior. By subtracting the UAV ground speed and attitude
from the airflow vector, wind speed anddirection can be calculated. Thus, a precise inertial measurement unit is crucial
to perform the UAV flight analysis.

ELLIPSE-N, CHOSEN FOR UAVFLIGHT ANALYSIS
Turbulence plays an important role in
the transport and exchange of energy
in the lower atmosphere. A high data
rate is required to record these very fast
fluctuations in the wind speed. “Wewere looking for a precise inertial measurement unit. Required specifications
were an accuracy in attitude anglesof <1°, and a high data output rate”
declares Uwe Putze, Dr.-Ing. at the“The Ellipse-N was selected because it fulfills all the requirements and provides a unique balance of accuracy, size andweight”
Dr.-Ing. Uwe Putze

SUCCESS STORY - MASC
Eberhard Karls Universität Tübingen.
As the unit had to be mounted in asmall unmanned aerial vehicle, small
size and low weight were also important for the project. “The Ellipse-N was
selected because it fulfills all the requirements and provides a unique balanceof accuracy, size and weight”, adds theProject Engineer. Small-size and lightweight, the Ellipse-N offers more thanattitude and heading measurement. It
fuses inertial data with GPS and pressure sensor information to provide arobust position and an enhanced altitude accuracy. The report showing thesensor dynamic calibration over the fulltemperature range made the team evenmore confident that the system would
meet the announced specifications.

HIGH QUALITY DATAThe Ellipse-N has been easily integrated into the on-board measurement
computer through a serial interface.
While the airflow probe measures airspeed and incident angles, the Ellipse-N
records the UAV position, ground speed,
and attitude angles. Raw data is stored

Sensing GPS + Inertial

AIRFLOW ORIENTATION CORRECTION
Pitch

WIND SPEED DEDUCING
Airflow- Aircraft Speed
Air Flow Probe= Wind Speedin the computer, and can also be displayed in real-time on the ground station, thanks to a telemetry link.
By using this sensor, the system canmeasure wind speed with an accuracy of +/- 0.5 meters per second in all
threes axes, and record speed variation at up to 20Hz. The output rate of
200Hz made any data interpolation
unnecessary.

WHAT’S NEXT?
The measurement system has beentested in several field campaigns. Basedon various results and experience, theEnvironmental Physics Group works on
improving the system and data analysis
tools to further increase accuracy.
As the Ellipse-N performed so wellduring tests, the group is alreadyintegrating the sensor in many otherresearch aircrafts.
 Dr.-Ing. Uwe Putze, Eberhard Karls
Universität Tübingen& Hélène Leplomb, SBG Systems

ELLIPSE-N KEY FEATURESABOUT THE PROJECT»» 0.2° Attitude, 0.5° Heading

The Environmental Physics group is part of theEberhard Karls Universität Tübingen. The fundamental aim of this group is to promote physics
within the context of the environmental sciences.
At the Eberhard Karls Universität Tübingen, turbulent atmospheric flows are mainly studied using
automatically operating unmanned airborne vehicles (UAV). Different classes of automatically operating UAVs are under development, mostly lightand small electrically powered aeroplanes.

»» 2 m Position accuracy»» Accurate attitude even in high G maneuvers»» Precise UTC referenced output and SyncOut
signal»» Automatic magnetic declination and local
gravity»» Integrated Kalman Filter

More information:
http://www.geo.uni-tuebingen.de/umphy

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