Adding photos and aligning stereographic pairs is the first most important step, and is influenced a lot by the quality of the images and the overlap

Creating mesh can be useful in adding ground control points as it better estimate the location of the GCP.

This step is recalculating the camera parameters, transforming the scale and rotation of the scene.

This step is useful for more accurate orthorectification process. There is a tradeoff between computational time and accuracy.

The final step where the images are compiled into an orthorectified mosaic. If the DSM has gaps this can be substituted with DSMs from other sources (e.g. ALS)