Geodetic measurements of deformation at Long Valley caldera provide two examples of the application of principal component analysis. A 40-line trilateration network surrounding the caldera was surveyed in midsummer 1983, 1984, 1985, 1986, and 1987. Principal component analysis indicates that the observed deformation can be represented by a single coherent source. The time dependence for that source displays a rapid rate of deformation in 1983-1984 followed by less rapid but uniform rate in the 1984-1987 interval. The spatial factor seems consistent with expansion of a magma chamber beneath the caldera plus some shallow right-lateral slip on a vertical fault in the south moat of the caldera. An independent principal component analysis of the 1982, 1983, 1984, 1985, 1986, and 1987 leveling across the caldera requires two self-coherent sources to explain the deformation. -from Author