Improved Pressure Sensitive Paint Measurement Using Natural Feature Tracking and Piecewise Linear Resection

Wind tunnel Pressure Sensitive Paint (PSP) ratio techniques require accurate registration between wind-on and wind-off camera image pairs. The Piecewise Linear Resection (PLR) method of removing registration due to physical wind tunnel model motion and deformation errors can account for nonlinear deformations and benefits from increased tracking point coverage in the image. This work presents a method to increase the accuracy of PLR by tracking natural features in addition to standard fiducial markers. This is accomplished with Speeded-Up Robust Features (SURF) and a modified disparity gradient filtering technique. This work shows that this method of automatic PLR is feasible on wind tunnel imagery and that the resulting pressure data has reduced mis-registration noise without the need to perform 3D resection using virtual models and pre-defined deformation equations.