Picture of compact distrometer

Intelligent Sensor Unit

Indoor User Terminal
(click on the screen to get a feeling about the User Interface)

Indoor User Terminal

Figure 1:The 2D-Video-Distrometer

The 2D-Video-Distrometer is a precipitation gauge, working on the basis of video cameras.
It has been developed by
JOANNEUM RESEARCH in cooperation with ESA/ESTEC (European Space Agency / European Space and Technology Centre) for research purposes. Students of the Graz University of Technology / Austria have also contributed to the work presented.

This homepage presents information on the instrument and on measurement results.

'Tall' standard version of 2DVD with raingauge

What does the 2D-Video-Distrometer do?

Originated in the area of weather radar and propagation research, the 2D-Video-Distrometer is now suited for all kinds of applications where details on precipitation are of interest.

In the left part of Figure 1 the outdoor part, consisting of the Sensor Unit (SU) with the Outdoor Electronics Unit (OEU) closeby is shown.

The new design shown in the middle of Figure 1 only consists of a Sensor Unit (SU) equipped with intelligent cameras doing the data processing and compression.

The Indoor User Terminal (IUT) is actually a standard PC / Laptop, the right part of Figure 1 shows screen, mouse and keyboard.

Figure 2 presents the IUT main screen of the Indoor User Terminal, summarizing the features of the 2D-Video-Distrometer.

Of each single hydrometeor reaching the measuring area the front- and the side view and the vertical fall velocity are measured and recorded. Online as well as offline the following displays are available:

rainrate vs. time, dropsize distribution, vertical velocity vs. equivolumetric diameter, horizontal velocity, oblateness vs. diameter.

These five displays, an oblateness distribution diagram and the single hydrometeor display may be selected for full screen representation with additional information and further menu choices. A top view of the measuring area is drawn in the middle of the main screen.


What are the specifications of the instrument (Compact version)?

Loughing face

Advantages of the measurement principle:

Alignment sketch

About data rate and precision of alignment:

The raw data rate of each of the two high-speed line scan cameras is 40 MByte per second, resulting 80 MByte of data per second processed.

Alignment precision requirement: in the order of 1 foot per 1 mile.

Sample drop

Here are some selected samples of data:

First of all a series of 9 water drops with approx. 1 mm diameter steps is given.

Then four different precipitation situations are presented: widespread rain, storm, melting snow and snowfall. The shapes of hydrometeors, their fall velocity and size distribution indicate quite clearly the kind of precipitation.

Figure 3 represents a widespread rain event, confirming very well the relationships v(D) taken from literature. Figure 4 presents the measurements of an even smaller number of drops than in Figure 3, being widely spread around the mean values expected. A thunderstorm is recognized. Drop shapes in storms differ quite significantly from the Figures given in the literature. In Figure 5 the influence of heavy horizontal wind forces is clearly recognized. The drop passes the side view camera (blue shape) from the right to the left side at an angle to the vertical of around 45 degree, obviously being accelerated by the wind or by turbulences near to the ground and therefore flattened at the right side. The front view camera (red shape) records the drop moving downwards at an angle of around 45 degree directly into its face with a shape differing not much from the expected figure. In this case the front view is not as oblate as it would be expected in situations without any horizontal forces. For comparison in Figure 6 the views of a drop in stagnant air are shown.

Figure 7 and Figure 8 identify melting snow. In the vertical velocity versus diameter diagram (Fig. 7) it is recognized that small particles are completely melted yet, they follow the theoretical values closely. The bigger particles are still mixtures of ice and water, they have not reached the terminal fall velocity of raindrops and they show quite irregular shapes. Figure 8 gives an example.

Finally snow data shall be presented. Figure 9 clearly indicates, that snowflakes of any size are hardly faster than 2 m/s in fall velocity.

Snowflakes present totally irregular shapes to the camera, Figure 10 give an example. Such data provide detailed information and allow unprecedented investigations on snowfall, [e.g. Hanesch et al., 1998; Barthazy et al., 1998; Vaxevanakis, 1999], its interaction with electromagnetic waves and also of growth and structure of the snow cover.

DSD diagram

Samples of analyses

Figure 11 shows a Rainrate vs. Time diagram for a short convective event on June 18, 1997, 17:00 - 19:00 in Graz / Austria with rather moderate rainrates (not exceeding 30 mm/hr). The DSD for the most intense period of this event (17:54 - 18:00) clearly indicates drops of more than 7 mm in equivolumetric sphere diameter. Distrometer-derived reflectivities show considerable differences, based either on the rainrate or on DSDs.
Tropical DSDs frequently present a contrary behaviour in comparison with moderate climate storms.
Canting angles of axially symmetrical particles may be determined. Before however distortions of horizontally moving particles, introduced by the line scan camera measurments, have to be corrected. Figure 16 shows a distorted image, the approximate and the precise correction. Further samples of canted raindrops are shown.

2DVD in hail chasing van

A mobile employment in a hail chase van has been done!

One 2D-Video-Distrometer has been mounted in a hail chase van for the Field Campaigns 1995 and 1996 of Colorado State University (CSU). The campaigns were managed by Prof. V.N. Bringi. The CSU Chill Radar was employed, one electricity and two hail chase vans and the T28 aircraft of the South Dakota School of Mines and Technology (contact person: Dr. Andrew Detwiler). Several storm events have been recorded, allowing detailed comparisons of radar reflectivities with in-situ measurements. As examples the front- and side view of two hailstones are presented in Figures 17 and 18.

2DVD with avalanche research project

Avalanche Research in the Alps

For enhanced avalanche warning systems research activities were carried out in the Alpine Mountain range not far from Graz / Austria. The 2D-Video-Distrometer data used for detailed investigations of the structure of the snow cover. Installation took place in November 1999.

Drop oscillation experiments Jauntal

Drop oscillation and canting angle experiments

At an 80 meter railroad bridge (Jauntalbrücke) near the village of Ruden in Carinthia / Austria an experiment to study drop shapes, their oscillations and canting angles was carried out. The experiment was initiated by Prof. Bringi, Colorado State University. For several days a fire brigade water hose was used under calm wind conditions to create significant artificial rainrates.

Special thanks to Jauntal Bungy Adventure ( http://www.bungy.at/en/ ) and to the Fire Brigade Untermitterdorf (http://www.ff-untermitterdorf.at/) making possible the experiment with their voluntary and generous support !

2DVD for industrial measurements

A tool for meteorologists only?

The excellent possibilities of the 2D-Video-Distrometer do not only address meteorologists and persons interested in precipitation, but also scientists working in different fields.

Contact us and we will be pleased promptly to send you our proposal solving your measurement tasks.


A commercial product, used all over the world

Cf. end of table of customers / partners

Here is a list of our customers/partners:

Logos Organisation / Enterprise and (relevant) link  
ESA Logo European Space Agency
Logo of Papua New Guinea University of Technology Papua New Guinea University of Technology
(Papua New Guinea)
see pictures
Logo of Colorado State University Colorado State University
see pictures
Logo of Iowa Institute of Hydraulic Research University of Iowa
Logo of ETH Zürich ETH Zürich
Logo of NOAA National Oceanic and Atmospheric Administration (NOAA)
see pictures
Logo of Institute of Atmospheric Physics of the Academy of Sciences of the Czech Republic Institute of Atmospheric Physics of the Academy of Sciences of the Czech Republic
(Czech Republic)
see pictures
NASA Logo National Aeronautics and Space Administration (NASA)
see pictures
Logo of the National Central University (Taiwan) National Central University
see pictures (unit #6)
see pictures (unit #9)
Logo of the National Observatory of Athens/Greece

National Observatory of Athens

see pictures
Logo of CRL Japan National Institute of Information and Communications Technology (NICT)
(former CRL, Japan)
see pictures
Logoof National Chiao Tung University Taiwan National Chiao Tung University (NCTU)
see pictures

National Center for Atmospheric Research (NCAR)

see pictures
Shimane University
see pictures
Hokkaido University
see pictures
USDA Forest Service
see pictures
We have to commit that we were not able to keep this table up-to-date during the last months.
We apologize to our valuable customers that are not contained in this list and will update a.s.a.p. after getting the permissions to do so.

And who did the work?

References (including some downloadable documents in PDF format)

Links to other sites dealing with the 2D-Video-Distrometer

Remark: Clicking on certain links within distrometer.at or any of JOANNEUM RESEARCH's hosted sites will take you to other Web sites for which JOANNEUM RESEARCH takes no responsibility.

Search for Video Distrometer

Photograph of Dr. Schönhuber

For more information please contact:


DIGITAL - Institute for Communication and Information Technologies
Space and Communication Technology

Steyrergasse 17
A-8010 GRAZ
Austria (Europe)
Tel: ++43 - 316 - 876 - 2511
Fax: ++43 - 316 - 876 92511
e-mail: Michael.Schoenhuber@joanneum.at

Last update of this homepage: 2013-09-24

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