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Environmental Studies |
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Introduction to our work with satellite telemetry |
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Telemetry with the Global Positioning System (GPS) is an efficient and often cost effective method to monitor the movements of animals as well as being the most accurate in determining spatial and temporal locations. Since the investigation areas only have to be entered once to outfit the animals with a GPS collar, this method also promotes environmental protection. In addtion the instruments can be re-used several times. The investigated animals should be encumbered as little as possible by the collars which are adapted in size and weight to the body weight, anatomy, and gaits of the respective animals. We work together with the company VECTRONIC Aerospace which makes GPS collars and continuously improves them. All statements relating to GPS collars are based on instruments from this company. Development of own investigations: Our projects in chronological order present a history of the
technical development of GPS collars. The prototypes developed in 1994 by VECTRONIC Aerospace (then Engineering Office Schulte) were relatively large, up to 1.8 kg heavy, and constructed in such a way that they
stored certain localizations of the animals and subsequently transmitted these via the communication satellite TUBSAT-A (Technical University Berlin Satellite) to the ground station in Berlin. A relatively
great amount of energy was needed for this data communication so that the collars were correspondingly heavy. The instruments were also protected by a special plastic covering to withstand environmental
conditions (Fig. 1 on the right).
Fig. 1: The first GPS collars developed by VECTRONIC-Aerospace in 1994 for monitoring the
movements of red deer prior to use (left picture) and after two years in the field (right picture) The telemetric investigation of red deer begun in the winter of 199/95 were among the first worldwide to be conducted with GPS collars on wild animals. In order to investigate the spatial-temporal behaviour of European wild sheep and reindeeer smaller and lighter instruments had to be developed in the following years. Such an instrument is presented in Fig. 2. The GPS receiver and the satellite antennae are housed at the top of the collar, the electronics, the batteries, and radio transmitter are at the bottom. Both casings are connected with a cable running through the collar. This collars are used in 1996-1998 in tracking studies
Fig. 2: GPS collar Model 2TDD by VECTRONIC-Aerospace The projecting wire is an antenna that can send signals from the radio transmitter as well as position coordinates to the ground station. The weight of the GPS collars depends mainly on the number of batteries used which provide the energy for the localizations. The depicted instrument weighs 700 g and can record up to 4800 position coordinates for which the rhythm of data collection can be adjusted to the desired time period.
All data are stored permanently in the GPS collars and can be directly read through an interface from a personal computer. Data evaluation with a GIS: The locations of the animals are stored as Cartesian coordinates. For further evaluation the data are converted to Gauss-Krueger coordinates and transferred as dBase files to a geographical information system. For the construction of the GIS various thematic maps of the investigation areas are digitalized and overlaid with the position coordinates of the investigated animals. The data is analyzed using the software ArcView (Company ESRI ) and Animal Movement Analysis ArcView Extension (Alaska Biological Science Center). Calculation of ranges: The range of an animal is defined as the area it frequents during a
given time period for the fulfillment of its normal activities such as feeding and reproduction. In our studies the range sizes were calculated using the Convex-polygon Method. In this method
all locations of an animal are graphically depicted, and the outer position points connected in such a way that a convex polygon is produced (Fig. 3).
Fig. 3: Determination of the size of a range (blue area) according to the convex-polygon method. Localization points of European wild sheep Nr. 53 connected in chronological order (n=1224)
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