Hi Everyone
Im putting together a UAV for aerial surveying using stereo photogrammetry.
Id like to get some input for the experts before going ahead.
My plan is to buy a high wing trainer coupled with an APM2.
Electric powered with a gyro camera mount.
The software Im using is photomodeler scanner. It can do DSM.
Im quite a n00b when it comes to fixed wing, but I have got a fair amount of expericence on multi-rotors.
Im doing this on a fairly tight budget and need to know a good camera to use.
Any advice would be greatly appreciated and will gladly buy any1 a beer if you're ever in South Africa :)
Thanks!
G:)
Replies
Regarding how we control the Samsung NX200 -
I open the cameras and connect wires to the focus and snap switch lines. The camera is then neatly closed with a mini connector located in the battery compartment. This is then controlled by the autopilot during the photo mission. The flight plan is set for the correct height and photo interval for the correct photo overlap for the required GSD.
The samsung lenses are no good for this application - they are fly-by-wire lenses and will not remain at a manual focus setting when the camera is switched off and of again. In auto-focus mode they are too slow and the time between photos suffers - we go down to 0.7sec between photos and the lens insists on refocusing each time. The Pentax 21mm lense is superb - very low distortion. Used with the Samsung/pentax adapter which has a manual aperture ring, so easy to set aperture and take photos in aperture priority mode.
The downside is the weight - camera plus adapter plus pentax lens is around 500grams...
Pentax lens is around 240grams, the 15mm pentax lense , also a VERY good lens with low distortion, is even heavier.
The best lense for this is in fact the Voightlander 20mm or 15 mm lense with adapter. it is half the weight of the pentax lens, perhaps better quality in photo, and the adapter is 12grams compared to the samsung 66grams...I have not managed to find the Voightlander lense in my part of the world yet - B&H camera in NYC have them at good prices.
Joe
I think there are three important things that must be together to choose the best camera:
weight, sensor size (22 x 14 mm or higher) and barrel distortion.
To see distortion check
http://www.imaging-resource.com/camera-reviews
To more accurate we need the tangential distortion but it isn´t on the database and I think is too hig
@Joe, Could you please tell me how you set and control the Camera (SAMSUNG NX200/210)?. What difference between the Samsung lens and Pentax. I think it has 16mm in the kit.
Cheers,
UAVOZ
I've done a little bit of background work in the evaluation of DEM accuracy for small UAV missions.
Have a look at my 2012 research on UAV derived DEMs.
Got a link that actually shows the research details, and not just abstracts?
Dont waste your time with Photomodeler....Have tried a number of softwares and to date the best performer is Agisoft ( google it) It works exceptionally well and generated full stitched images with very good DTM's and fully orthorectified imagery.
Generates very good outputs for survey grade data and works well for mine applications as well, eg, stockpile volume determinations, etc.
Check my posts on SurVoyeur - we have now flown more than 900linear km of area and processed all the imagery with Agisoft, with survey grade results ( better than 4cm horizontal ground accuracy and 7cm vertical accuracies), and satisfed customers!
Not sure what other posters are implying re CMOS sensors - nothing to do with sensor type as far as vibration, etc. For the best results:
At least a 18Mpixel camera. Samsung NX200 or NX210 is what we use - 20Mpixel, with Pentax 21mm Prime lens - one of the best performers with regard to barrel distortions. 21mm allows reasonable flight heights for good ground resolutions. We are currently evaluating the Pentax 15mm prime lens as well, which may be even better suited. However, I suspect the VoigtLander 15mm lense might be the real solution, it is a bit more than half the weight of the Pentax 15mm lense, with the same performance, it claims.
The Sony NEX seies are more popular than the Samsung NX range, but the NX5 is only 16Mpixel and that is NOT good enough for when used with the 15mm lens - 15mm lenses allow much greate area coverage for a given height, and coupled with high pixels sensors allows down to 4cm ground resolution with ease. The Sony NEX7 is 22Mpixel, BIT is 120grams heavier than the Samsung. Also it is about 1.7times the price!!
Support from Agisoft ( Russian) is VERY good. We fly with 60% forward overlap and 60% side to side overlap in imagery - implies lots of photos to process, but you need that to be able to generate the accuracies in ground resolution needed for survey grade data. Don't let anyone tell you otherwise - if they do , they have never put there data to a true accuracy test!
It is also useful to stablise the camera in the roll axis - any light weight fixed wing plane is more agile in roll than pitch, and this helps the photograph sightline, although this can be compensated for by flying with greater side overlap = just means longer image processing times. We also do road and pipeline surveying, and a roll stabilised camera is very usefull here - the roads and pipelines have 'kinks' that require the A/C to roll - so camera stabilisation helps.
Most important for data accuracy. however, is that you have MANY tie points, ie, photographically visible target, accurately placed with survey grade GPS systems. These are then used by the processing software to 'morph. the skewed photographs into accurate orthorectified data. The more tie points the better.
Hope ths helps..
Cheers.
Joe, The NamPilot, Namibia..
Hello Gareth,
Good to hear someone else using photomodeler scanner. From my research, this is the software I'll be using too. I plan to use ground control points to give scale to the project and improve accuracy. Eventually I hope to use hardware to give precise RTK GPS coordinates of the camera for each picture, potentially negating the need for ground control points. My goal is to make topographic surveys accurate enough for engineer design use. I have not picked a best camera yet, but it will be a mirrorless non-zoom lens camera. Sony is coming out with a new "RX-1" fixed lens mirrorless full frame 24mp camera, but it's not cheap, $2,600. I'm budgeting for a $600 model. I read somewhere else on here that CMOS chip cameras should be avoided, that they do not take good pictures because of the vibration. I do not know if this is true. Most all cameras use this type of sensor. Good luck with your progress. I'll be looking at the forum for all photogrammetry related posts.
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