Difference between revisions of "Snow height - ultra sonic sensor"
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Starting a measuring cicle in the SR50 from the DL2E was difficult, because the pulse generated in the DL2E was too long. In the end a solution using a micro controller was found. | Starting a measuring cicle in the SR50 from the DL2E was difficult, because the pulse generated in the DL2E was too long. In the end a solution using a micro controller was found. | ||
| + | The measurement of snow depth is an important parameter for the measurement of the snow cover in the terrain. Its formation is subject to strong variance, based upon time and space factors. Influencing factors here are the development of snow cover, under the influence of further climatic events (air temperature, wind, global radiation), the characteristics of the land, as well as the spatial distribution of precipitation in an area. Because of these factors, the selection of a suitable location for measurement is decisively responsible for whether this is representative for an area or not. | ||
| + | ==Selection of the Measuring Location:== | ||
| + | The right selection and positioning of the measuring location is of very great importance. The field of measurement to be recorded should be most preferably flat, protected from wind and secured against avalanches. Steep hillsides, hollows, terrain edges or large rocks in the immediate vicinity of the measuring location should be avoided. Steeply sloping fields of snow harbour the danger that the snow cover could begin to slide, thereby falsifying the measuring results. To ensure a problem-free measurement, the sensor must be aligned parallel to the ground. A minor incline of the ground can be compensated for by a correct alignment of the sensor, using the holding fixture provided. Furthermore, the expected snow depth at the | ||
| + | location should be estimated, in order to assure a suitable mounting height for the sensor. | ||
==Links== | ==Links== | ||
Revision as of 14:10, 7 October 2008
Parameter to be measured:
Snow height
Method:
Ultra sonic sensor
Equipment:
Ultra sonic distance sensor: e.g. Campbell Scientific SR50 or USH-8 from company Sommer
Logger: Campbell recommend their loggers. But it can be connected to other loggers, e.g. a DL2E from Delta-T
Advantages:
- Continous measurement
Disadvantages:
Measurement principle: The velocity of an ultrasonic signal in air depeding on the air temperature. For an accurate measurement of the snow height the puls length wich is proportinal to the distance has to be calibrated by the airtemperature. Sensor Campell SR50 use an external temperatur sensor and calculate the temperature compensation in the Campell data logger. The Sommer USH-8 use an internal temperature compensation and outputs the already compensated snow height to any data logger.
Measuring during snow fall is quite dificult because every snow flake produce additional reflected ultrasonic pulses. High-end sensors like, Sommer or Campell, can handle such additional reflections and measure reliable also during snow fall.
- Expensive high end sensors
- While the sensor itself without control electronic is cheap (about 10$ for robotics) connecting it to a logger requires quite some knowledge about digital electronics and programming. The signal from the sensor is usually a puls with a length proportional to the distance. Therefore, the more expensive (> 1000$) sensors from scientific instrumentation companies are usually used.
Problems/Questions:
Starting a measuring cicle in the SR50 from the DL2E was difficult, because the pulse generated in the DL2E was too long. In the end a solution using a micro controller was found.
The measurement of snow depth is an important parameter for the measurement of the snow cover in the terrain. Its formation is subject to strong variance, based upon time and space factors. Influencing factors here are the development of snow cover, under the influence of further climatic events (air temperature, wind, global radiation), the characteristics of the land, as well as the spatial distribution of precipitation in an area. Because of these factors, the selection of a suitable location for measurement is decisively responsible for whether this is representative for an area or not.
Selection of the Measuring Location:
The right selection and positioning of the measuring location is of very great importance. The field of measurement to be recorded should be most preferably flat, protected from wind and secured against avalanches. Steep hillsides, hollows, terrain edges or large rocks in the immediate vicinity of the measuring location should be avoided. Steeply sloping fields of snow harbour the danger that the snow cover could begin to slide, thereby falsifying the measuring results. To ensure a problem-free measurement, the sensor must be aligned parallel to the ground. A minor incline of the ground can be compensated for by a correct alignment of the sensor, using the holding fixture provided. Furthermore, the expected snow depth at the location should be estimated, in order to assure a suitable mounting height for the sensor.
Links
Projects that used the above equipment
- http://brandenburg.geoecology.uni-potsdam.de/projekte/malalcahuello/index.php
- http://brandenburg.geoecology.uni-potsdam.de/projekte/opaque/index.php
Other related web sites