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Mt. Kilimanjaro Orthometric Height by TZG08 Geoid Model and GPS Ellipsoidal Heights from 1999 and 2008 GPS Campaigns

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Abstract

Mountain Kilimanjaro is the highest mountain in Africa; it is located in Tanzania on the northern border of Tanzania and Kenya at latitude and longitude.

Several attempts to obtain the exact height of Mt. Kilimanjaro using different survey techniques have been deployed since 1889. Documented results show height range between 6010m in 1889 and 5891m in 1991; differing by as much as 120m. The 1952 result of 5,895m above mean sea level (msl) has remained the official height of the mountain to date. After 1952, two attempts were made to obtain the orthometric height of the mountain using modern approach of GPS levelling; a technique that requires accurate ellipsoidal and geoidal heights. During the two last attempts in 1999 and 2008, accurate ellipsoidal height was obtained by geodetic GPS positioning at Uhuru peak, the highest point on Kibo cap. Due to non availability of precise and accurate geoid model for Tanzania, the 1999 height was obtained as 5892m and the 2008 height was 5891m. The major cause of the significant vertical difference of up to 4m from the official height is attributed mainly to absence of precise geoid model, since the ellipsoidal heights from the two GPS campaigns are essentially the same. Tanzania has now a dedicated precise gravimetric geoid model, TZG08, which was carefully computed to take care of rough mountainous topography, besides it is compatible with Global Navigational Satellite Systems (GNSS) which includes GPS. Evaluation of the four most recent global and regional geoid models for Tanzania using different approaches have all passed TZG08 to be the best gravimetric geoid model for Tanzania for the time being.

The aim of this paper is to compute a more accurate orthometric height of Mt. Kilimanjaro by utilizing the current most precise geoid model for Tanzania,TZG08, together with the 1999 and 2008 GPS campaigns ellipsoidal heights using GPS levelling method.

Result of the GPS levelling using TZG08 gravimetric geoid model and the Kil_1999 and KILI2008 GPS ellipsoidal heights, is that the orthometric height of Mt. Kilimanjaro is 5,894.94m. Therefore the orthometric height of Mt. Kilimanjaro is practically the same as the 1952 official height of 5,895m.

 

Keywords: Mt. Kilimanjaro Orthometric height, Tanzania TZG08 Gravimetric Geoid Model, Kil_1999 and KILI2008 Mt. Kilimanjaro GPS Campaigns Ellipsoidal Heights

References

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Published

2015-10-30 — Updated on 2015-10-30

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Vol. 2 No. 1 (2014)

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