Flightpath outside the defined polygon

You can do this by selecting the Connectionless mode. In the Active Connection mode that is shown here images are only taken inside the polygon while the aircraft is at the prescribed speed. Having all the images taken while travelling the same speed will yield better results. You can use the Connectionless mode but the images will be taken at mixed speeds. 

https://support.dronesmadeeasy.com/hc/en-us/articles/217006946-Connectionless-Mapping