Aerial Survey - Please help!

[bluesideoops]

Hi,

Survey gurus - please help! On a limited budget, around $3000 USD and need some equipment to take some aerial photography of farmland - Sony Nex-7 and GoPro Hero3 seems to be a good option.

So, please provide some info:


What is the best camera and accessories for this kind of work?
Which option will give best battery life etc?
Which has an internal GPS or some way to refer to the time/position during the flight?
How can it be mounted on the aircraft (e.g. strut or through a removed panel) or is better through removed door so no airworthiness implications?
Any other information that you can provide??
What is the optimum altitude to take photos and is there a simple calculation to figure out what the coverage will be for a given altitude (also is this lense specific)?
What sort of shutter speeds should be used?

I know there are many gurus lurking about out there and I know nothing, so please hit me up with advice or ask more questions so I can clarify any points. One big question everyone probably asks is why not just hire some aerial photography experts, well the problem is we do not have enough budget!


Thanks

[Bye]

The question with all data gathering is what is the data going to be used for.

this will determine what level of equipment is needed to gather the data.

so for example if you want high altitude overall shots of the whole of a farm like on google earth you need a certain set up.

or you may be better off with a good photographer shooting through the open window of a high winger, with a range of lenses to get shots that can be stitched together to make a large collage that can be printed on say an A0 printer as a large picture or in smaller but higher details pictures.

what sort of detail on the shots do you need, ie what resolution will be key so that is your first question, what do you intend to use the pictures for?

if you want large format, very high res overhead as opposed to oblique shots again, you can do it with a good DSLR and the right lenses if you want to busk it and spend plenty of time post processing, or you can pay for pro mapping shots.

re optimum altitude, yes the amount of coverage for shots depends on the lens fitted and of course altitude and will depend on resolution of camera etc, so lots of high res, stitched together would be my advice for high res, but if the finished picture is say for a large display shot to the public the quality may not be up to it,

if its just for some grubby real estate seller, give em nothing.

if its for internal use, then a stitch job may be good enough, as i say your output needs will determine your input process.

[FlightPathOBN]

Make sure that you put targets out there. With a known length and width, the images can be georeferenced by the target. This will also allow the images to be spliced together at the targets.

http://www.state.nj.us/transportation/eng/documents/photogrammetry/images/image020.gif

Plan it out, and place the targets accordingly.

Since you have the GPS location of the targets, you can bring them into any program, Autocad or Google Earth.

I have Autocad Civil 3D, so I can connect them if you would like, just PM me...

you would probably want to fly at about 1000 feet.
http://operationsbasednavigation.com/wordpress/wp-content/uploads/2013/05/GoogleEarth_Image-1-e1369759364606.jpg

[FlightPathOBN]

The Hero 3 has a fixed focal length, reported to be 27.7mm.

The Sony does not have a fixed lens, so you will be able to get a better choice of lenses for the adventure, such as a fixed focal length 85 or 135mm.

It also shoots in RAW mode, which depending on your use, would be very important.

Removed door with simple bubble mount on the camera would probably suffice

Edit: approx field of view calcs

135mm at 1000 feet= 178' (x) and 118' (y)
85 mm at 1000 feet= 282' (x) and 188' (y)

with the Hero 3 you could fly at 400' to get a 300' (x) and 200' (y) but with much more distortion at the edges...

[FlightPathOBN]

If you have the ability to install something like this, they really help..

http://farm3.staticflickr.com/2633/4061018353_22dd15fa76_z.jpg?zz=1

http://content.answcdn.com/main/content/img/McGrawHill/Aviation/f0014-02.gif

Then of course, you should plan the flightpath...give the pilot gps coordinates to fly...

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRg1iqjMc2FCUNobrkSPrSUMNuqdKegsAN0Wh3vfAG OApp-m72_

[bluesideoops]

Many thanks for all the replies and helpful advice - the area we are photgraphing is huge and straightline distance will be about 1600NM, we require quite high resolution to be able to see ground features quite clearly (hence why I am quite keen on the Sony Nex7) and understand what some of you have said about edge-blurring, which leads to another question - is there a calculation for the shutter speed for a given TAS?? or is something like the Nex7 clever enough to be able to avoid such problems. What we may do is get a Hero3 as backup and take video on HD then take still from that - any thoughts?

[FlightPathOBN]

typically, a mosaic is shot with about a 20% overlap to take care of the edge issues...

If you are taking images from the same altitude, the Nex will look quite a bit different that the Hero.

There is the video capability of the Nex as well, but you will need quite a bit of memory.

This adventure is going to take a lot of memory capacity, you need to figure in some of those terrabite backups, many have an SD card reader built in...

[bluesideoops]

Hi FlightPathOBN,

Thank you for sharing your wisdom, you evidently have a huge amount of knowledge here - one last thing, you mention a bubble-mount for the camera, is that something you can buy off-the-shelf or do you have to make it? and is there risk of distortion?

I really want to make a vertical mounting on the aircraft that is:
A) easy to install
B) won't lose the camera
C) will have minimum affect on the camera in terms of vibration/airflow
D) will avoid involving aviation authority/manufacturers as a 'modification'

I am considering the following, if not ridiculously expensive:

CessnaCam Airborne Sensor Pod | Airborne Scientific Inc. (http://www.airbornescientific.com/content/cessnacam)

Cheers

[FlightPathOBN]

Thanks for the kind words....I have been doing this for airport surveys and obstacle assessments for procedure design...

Going low tech, but pretty safe is this approach...(with perhaps a safety line to the camera) make sure the pilot has some input into the clamp system...

http://farm4.staticflickr.com/3237/2768402272_def7fa7b0f.jpg

(but I dont like that hard mount for the camera, use a rubber isolator)

similar to this concept..
http://www.aerovideo.net/images/Bushings.jpg

[BOAC]

Way back I used to fly a 'corporate' Cessna310 for a Forestry Company, and we removed seats as required for survey work to install a Hasselblad and video cam vertically through a belly port. This enabled (Keith) to track (and correct) my flightpath (pre-GPS!) as he shot. Don't forget to make any corrective turns flat while filming to avoid distortion.

[bluesideoops]

Hi,

Really like the idea of this clamp system - does it require CAA approval or can you just go ahead and use it?

Cheers
B

[bluesideoops]

Hi,
Any chance that you can provide a picture of the bubble-mount - also where can we source one?
Thanks
B

[FlightPathOBN]

Well, if you use that clamp, I would just level with a magnetic strip and attach it to the clamp arm...

http://cdn.toolstation.com/images/130125-UK/images/library/stock/webbig/39452.jpg

As far as CAA approval, I wouldnt think so, but I would ask the pilot...its really their call...

The arm looks like it could handle 2 cameras, so you could do stills and video from the same perspective point.

[bluesideoops]

Legendary - thanks a million for your help!:D