Investigation of space-flight and landing conditions necessitates use of finite element human body models (FEHBMs) to simulate effects of loading. Current FEHBMs are developed with nominal geometry;​ there is significant interest in developing models with subject-specific geometry, especially for the spine where most of the loading under axial acceleration occurs. Methods exist for morphing FEHBMs from standardized to subject-specific geometry, but there is little investigation in reconstructing subject-specific spinal curvature. High contrast images of the spine are best obtained through CT scans and most capable machines are restricted to supine postures whereas subjects in crash and aerospace situations are seated. The objective of this study was to develop a transform function for occupants going from supine to seated postures for the purpose of these simulations. Visual observation of existing supine-seated scan pairs indicates a straightening of the spine in seated postures. Twelve human volunteers received supine and seated scans which were analyzed to determine change in vertebral position between postures and develop a transformation matrix that would predict vertebral displacement from supine-to-seated. The study also obtained supine MRIs of astronauts (n=9) and anthropometrically matched them to a corresponding human volunteer subject in order to derive an expected seated posture for the astronauts. Within the human volunteer data, the radius of curvature in the thoracic and lumbar regions was calculated and revealed that radius of curvature for seated subjects is significantly higher in the thoracic region (p=0.033), demonstrating that there is a straightening of the spine.