Browsing by Author "Polojarvi, Katja"

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    GPS collars in studies of cattle movement: Cases of northeast Namibia and north Finland
    (2011) Polojarvi, Katja
    The deployment of the US Global Positioning System can be seen as a mega-engineering project in itself. This GPS system consists of 24 satellites and has been operational since 1978; in 1984 the system has been open for civilian use. Spin off from this new technology has been a whole industry based upon GPS-navigation. This together with the advances in Geographical Information Systems (GIS) software has created industries based upon location based knowledge. We can give exact locations to any object, person or process on the surface of the earth, enabling us to produce real time spatial databases. How to incorporate traditional and indigenous knowledge into GIS-data is a fascinating problem. People’s memory of time and place is not exact, but there are markers in space and time which can be used to relate indigenous knowledge with more exact forms of data. Allowing for traditional forms of land use in a world dominated by other more advanced and intensive forms of land use is probably a very demanding task. There will be a need to integrate traditional knowledge with exact data on land use, wildlife, conservation, environment and management. This is definitely an important issue in engineering earth and the environment
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    Land use practices in Caprivi’s changing political environment
    (University of Namibia, 2013) Colpaert, Alfred; Matengu, Keneth K.; Polojarvi, Katja
    This paper presents an account of developments that led to present land use practices in the eastern parts of Caprivi and the eff ects these practices have on the ecosystem. In the pre-colonial period (–1890), the early inhabitants of east of the Kwando River were hunters and gatherers. Climatic and hydrological conditions enabled the fi rst Bantu communities to practice settled subsistence agriculture in the 18th and 19th centuries, a time when the Lozi and the Kololo kings ruled this area. Its location between perennial rivers made eastern parts of Caprivi good and easily defensible grazing area. Peripheral location and prevalence of malaria and cattle diseases made the area less tempting for European and South African farmers, but also made the colonial administration of east of the Kwando River diffi cult for Germany 1890–1915 and South Africa 1915–1990. The paper reviews published works and government documents, which is combined with fi eld observations and aerial photos of the area. In particular, our analysis focuses on Salambala conservancy because of its successes and many controversies. The analysis shows that indeed, enactments of law did not address land use in the manner that would have led to fulfi lment of the needs of subsistence farmers until Namibia’s independence in 1990. Nowadays, almost the whole area is still intensively used for small-scale subsistence farming and agricultural practices have remained traditional. The article describes the eff orts of previous administrations and outlines several factors that accounts for present-day land use practices. This account concludes that intensifi cation of grazing and clearing
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    Reduction of location error in GPS collar tracking data of bovine cattle by using data screening
    (University of Namibia, 2012) Polojarvi, Katja; Colpaert, Alfred; Matengu, Keneth K.
    Global Positioning System (GPS) telemetry enables tracking of an individual animal over a long period of time and can provide researches with accurate information on animal movement. However, various environmental factors influence the satellite signals received by a GPS collar, potentially deteriorating accuracy of position. We tracked Caprivi Sanga cattle using Televilt Tellus Basic GPS collars in North-East Namibia in 2006 and 2007. Locations obtained during the night, when the cattle are gathered inside livestock enclosures, revealed that a significant proportion of the locations are inaccurate. We used data of seven GPS collars for testing different data screening options as a way to reduce location error. Basic analysis showed that simple measures of accuracy like dilution of precision (DOP) and figure of merit (FOM) are not sufficient to remove erroneous locations from the data. We removed the inaccurate locations with the following condition: 2D location with DOP >6 or 0< altitude <850 m or altitude >1050 m or DOP ≥10 or FOM ≥10 or walking speed of the animal over 4.5 km/h. This data screening option eliminated 75% of the most erroneous locations (>300 m from the livestock enclosures) retaining 97.2% of the locations correctly located inside the livestock enclosures. Before data screening, 95% (1372) of the night-time locations that were located outside the livestock enclosures were located 71-406 m from the enclosures. The maximum error was over 10 km. After data screening, 95% (485) of the locations were 54-298 m from the enclosures; the maximum error was 4.4 km.