The present study deals with stereo digital image correlation (stereo-DIC) measurements associated with rigid body tests performed within the temperature range of polymer thermoforming. Indeed, stereo-DIC is recurrent in photomechanics to measure kinematic fields. However, in the presence of a thermal haze in the optical path, any change in the refractive index of the air causes distortion of the optical images and consequently a lack of precision in the measured displacements. The proposed procedure aims to quantify and then filter out systematic errors and noise induced by natural thermal convection. The measured displacement vectors were first used to evaluate the effect of temperature and the effect of rigid-body displacement speeds on the systematic errors and the noise of a pre-calibrated stereo-DIC system. Then, a post-processing procedure was proposed to filter the measurement errors. An application case was suggested to demonstrate that temporal filtering of systematic errors with consideration of the thermal haze corresponds to an approximate gain of 44%. The found results constitute an essential step towards the instrumentation of a thermoforming process