Sajama and Illimani, Measurements and Ascents. During 1994, in conjunction with the Military Geographic Institute (IGM) of Bolivia, I conducted differential GPS surveys of the mountains Sajama and Illimani. The purpose was to measure the heights of Bolivia's highest mountains. We used Trimble GPS 4000SSE Geodetic Survey receivers with geodetic antennas. The base stations were set up over first-order bench marks as close to the mountains as possible. The other receivers were carried to the summits and 30 minutes of satellite data were collected simultaneously with the base station receivers. The data was then sent to Karl Feaux at the University Navstar Consortium (UNAVCO) in Boulder, Colorado for processing. The software used to calculate the heights was the BERNESE GPS data processing package using the Ohio State University World Geoid Model by Dr. R.H. Rapp. The height calculated for Sajama is 6548 meters above MSL. The altitudes do not vary greatly from the generally accepted altitudes. The summitter of Sajama was Kyle Bohnenstiehl (AAC) who reached the top and operated the receiver in extremely high winds. He summitted by the southwest route. The summitters of Illimani were Gregorio Mamani and Donato Mamani of the Club Andino Boliviano, Hal Rundle and myself. We climbed the Normal Route. The base stations were manned by Sgt. Limache and Pablo Beltran from the IGM.

Liam P. O’Brien