Legal aspects aside, what is to be achieved by this survey? Is this for internal interest, archive, general placing of the pipeline in the surrounding countryside or more detailed records of the pipeline and the easement itself? Presumably it is not a legally required periodic safety inspection of a petrochemical pipe, is it?
Pipeline surveying is a pretty specialised business; you will achieve little in detail, I'd have thought, from 500', or do you plan to get an exemption? Are you really up to speed on 500'nav, following a feature that may or may not be well defined (older pipelines can be almost invisible), down amongst the fast pointy stuff...
Is the cameraman a Professional, or at least highly experienced? If not he will struggle to do anything useful out of a light aircraft, even if the door is removed which does not sound practical from the info given. Filming video or stills through a window, be it open or closed, is very difficult. I promise you hand held video from 500', even with a proper camera, will not tell you much except how pretty the countryside is, where the camera wobbles allow it to be seen at all. Stills photography form the air is a skill on its own, the light characteristics are not the same as on the ground.
Lots of other things to consider too, thermals, sunlight, contrast, haze, wind (the pipeline will be obscured by the aircraft at some drift angles)
It sounds to me like a job for a professional observer and/or a professional film outfit with a 'Blad and the correct lenses or a broadcast quality camera on a stabilised mount.
Last edited by Agaricus bisporus; 27th August 2008 at 14:12.