The Schottky barrier height of Ti and Pt contacts to Ga0.47In0.53As was measured using Franz Keldysh oscillations detected by electro absorption modulation, and compared to values obtained from the Schottky diode current voltage characteristics. Both methods reveal that the Schottky barrier height for holes in Pt contacts is 50-70 meV lower than in Ti contacts. The obtained barrier heights were used to calculate the specific contact resistance of Pt and Ti to p-type Ga0.47In0.53As. The results agree well with experimental data. A de-correlation method for improving the resolution of electro absorption data analysis is presented. An experimentally obtained correction factor for the measured electric field is introduced in order to account for a discrepancy between electro absorption theory and experiment.