If you want to rectify scenes from the same overflight that have overlap areas to each other, there is a way to quicker rectifying them than doing it for each scene individually.
Example: You want to rectify the scenes DS1036-2155DF050, DS1036-2155DF051, DS1036-2155DF052 and DS1036-2155DF053. Instead of collecting GCPs for each scene individually, you can use the overlap area between two scenes to process them quicker. In the following workflow it is assumed that you want to rectify the scenes in the direction from top to bottom (DS1036-2155DF050 to DS1036-2155DF053) - of course it is also possible the other way round.
1) Collect GCPs for the first scene (e.g. DS1036-2155DF050). Set 10-15 GCPs at the top of the scene and 10-15 at the bottom. The GCPs at the bottom needs to be in an area of the image that overlaps with the next scene (in this example: DS1036-2155DF051). Due to little differences in the width of the scenes, which is a result of the flight direction of the satellite, and due to the possibility of poor image quality in the corners of the image you should make sure that you leave a free space at the left and the right border of the scene where you do not set any GCPs (~2,000 pixels at each side of the image).
2) Use the collected GCPs to continue the process at the GCP conversion in 3_gcp_collection.md for the first scene (DS1036-2155DF050).
3) After finishing the rectification process of the first scene (DS1036-2155DF050), you can start off the GCP collection process for the next scene (in this example: DS1036-2155DF051) with already half a set of GCPs: Open the file with the collected GCPs from the first scene (the .points file) and delete all points that were set in the top area of the image. Save this file and open it in the QGIS-georectify window of the new scene (here: DS1036-2155DF051). You now already have the GCPs that belong to the top area of this scene. Those GCPs already have the correct reference coordinates. The x-image coordinates are also almost correct and give a good orientation about the actual position of the points in the image. Only the y-image coordinates are completely wrong. Using the "move" function, the GCPs in the image can now be moved up to their actual position.
4) Afterwards, collect further 10-15 GCPs in the lower image area, which are located in the overlap area to the next scene (in this example: DS1036-2155DF052). Use the collected GCPs to process the geo- and orthorectification of the second scene (DS1036-2155DF051).
For the third scene the same is done as described in steps 1 to 4.
Repeat steps 1 to 4 until you have rectified all the required scenes of the same flyover.
By reusing the points from the previous scene, the processing time of the following scene is significantly reduced. If several scenes of the same flyover are to be rectified, this can lead to great time savings with the same quality of results compared to the individual GCP collection for each scene.