We present the first application of the 3D cosmic shear method developed in Heavens et al .
( 2006 ) and the geometric shear-ratio analysis developed in Taylor et al .
( 2006 ) , to the COMBO-17 data set .
3D cosmic shear has been used to analyse galaxies with redshift estimates from two random COMBO-17 fields covering 0.52 square degrees in total , providing a conditional constraint in the ( \sigma _ { 8 } , \Omega _ { m } ) plane as well as a conditional constraint on the equation of state of dark energy , parameterised by a constant w \equiv p _ { de } / \rho _ { de } c ^ { 2 } .
The ( \sigma _ { 8 } , \Omega _ { m } ) plane analysis constrained the relation between \sigma _ { 8 } and \Omega _ { m } to be \sigma _ { 8 } ( \Omega _ { m } / 0.3 ) ^ { 0.57 \pm 0.19 } = 1.06 ^ { +0.17 } _ { -0.16 } , in agreement with a 2D cosmic shear analysis of COMBO-17 .
The 3D cosmic shear conditional constraint on w using the two random fields is w = -1.27 ^ { +0.64 } _ { -0.70 } .
The geometric shear-ratio analysis has been applied to the A901/2 field , which contains three small galaxy clusters .
Combining the analysis from the A901/2 field , using the geometric shear-ratio analysis , and the two random fields , using 3D cosmic shear , w is conditionally constrained to w = -1.08 ^ { +0.63 } _ { -0.58 } .
The errors presented in this paper are shown to agree with Fisher matrix predictions made in Heavens et al .
( 2006 ) and Taylor et al .
( 2006 ) .
When these methods are applied to large datasets , as expected soon from surveys such as Pan-STARRS and VST-KIDS , the dark energy equation of state could be constrained to an unprecedented degree of accuracy .