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Author Topic: Accuracy (round N)  (Read 20134 times)

fpbv

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Re: Accuracy (round N)
« Reply #15 on: December 20, 2012, 11:20:23 PM »
Lumix LX5 - very simple stuff tho :)

but 24 mm angle, which is quite good

George, this a very very very good camera and your problem is not the lens.
One problem is that not a full frame camera because has the some conversion lens factor.
I would suggest you use the some DSLR like Canon 5D MK II/III or Nikon, and use a fixed focal lens.
Zoom lens didn?t work as good as fixed ones.

If you want to know more pm.

 

ju523m

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Re: Accuracy (round N)
« Reply #16 on: December 21, 2012, 12:07:00 AM »
Hi all,

George, what options did you check in the optimization dialog? I had similar problems with various scene reconstructions and in the end I came to the conclusion NOT to check the skew and aspect option in the optimization dialog. For the camera setup I used, the things improved a bit, though the error was not completely eliminated.

Cheers

George

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Re: Accuracy (round N)
« Reply #17 on: December 21, 2012, 09:25:18 AM »
I check all 3 available options tho. Do you think it is related to the camera?

George

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Re: Accuracy (round N)
« Reply #18 on: December 21, 2012, 09:40:22 AM »
Hi Fabricio,
thanks. Do you use these cams?
G


George, this a very very very good camera and your problem is not the lens.
One problem is that not a full frame camera because has the some conversion lens factor.
I would suggest you use the some DSLR like Canon 5D MK II/III or Nikon, and use a fixed focal lens.
Zoom lens didn?t work as good as fixed ones.

If you want to know more pm.

fpbv

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Re: Accuracy (round N)
« Reply #19 on: December 21, 2012, 03:24:35 PM »
Hi George

The camera adds to the problem. The zoom lens is not recommended because their internal construction do not keep the distance focal all the way through.
Beyond that, you have the crop factor this kind lens have, so you do not have the real distance focal.
So, a profissional camera with a full frame sensor - without crop factor - and a fixed lens will give you a better results.
You can use a 24, 28, 35 or 50 mm fixed lens, it depends how higher you will flight and which are your purposes.
I?ve been using a Canon EOS 5D MK II with 21 megapixel with a 28 and 35 mm fixed lens.
I am looking for a new Nikon D800 with 36.3 megapixel or the new 5D MKIII.

I hope to helped you.

Fabricio

George

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Re: Accuracy (round N)
« Reply #20 on: December 21, 2012, 03:32:26 PM »
yeah cool. That sounds really cool!
Does it matter if all my zoom options are disabled at the camera settings?
Could you share some imagery of yours and may be a DEM as well if you can, please?
What kind of UAV do you have?

George

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Re: Accuracy (round N)
« Reply #21 on: December 21, 2012, 03:50:12 PM »
this is now the third round of optimization
Dark green - delta between DEM and DTM is just about +- 10 cm (perfect)
Light green - delta +- 20 cm (good)
Blue - +- 50 cm
Yellow - +- 1 meter
White and Black a vegetation
Red are strange patterns, since at the aerial imagery these are mostly exposed areas but the resulting delta is much bigger there, however, it should not exist there :(
I will go for more points and 4th round. Will see then

fpbv

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Re: Accuracy (round N)
« Reply #22 on: December 22, 2012, 01:39:57 AM »

Does it matter if all my zoom options are disabled at the camera settings?
 

You can do that, use zoom at minimum and do not use auto focus.
But still you can have some focal distance range, unfortunaly the lens geometry is not rigid for zoom lens for use in photogrammetry.
I still do not use UAV, I saw some here in Brazil but we are dealing with some legal issues to use it properly.
I think you could change your camera for this new mirrorless digital like Nikon N1, Samsung NX 1000 or Sony Alpha NEX 7, etc.

George

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Re: Accuracy (round N)
« Reply #23 on: December 22, 2012, 07:14:38 PM »
The optimization round number 4 gave an error of 2-5-10 cm. Will share the picture later! Cool!

piste

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Re: Accuracy (round N)
« Reply #24 on: December 23, 2012, 05:15:58 PM »
Hi guys...
I have George's same problem!
We use a canon G10 mounted on an UAV.
Photos are taken with minimum zoom and, obviously, with AF activated.
My workflow is the following:
  • Import photos
  • align them (without control point because we haven't yet camera coordinates available)
  • Edit > Gradual selection: delete points with a reprojection error greater than 1.0 (twice or three times maximum until reprojection error of chunck is low). I optimize the point cloud after every deleting operation (uncheck "Fit aspect" and "Fit skew").
  • Create geomoetry
  • Edit marker > Import .csv ot .txt file of control points
  • Optimize point cloud with control points imported (after placing them in the correct position = green flag )
  • Create Texture
  • Export

Following this workflow I have obtained results that seem very fine!! (error of 0,06 meters and 0,2 pixels).
Photos have been catched from 100 meters on terrestrial surface...
When I have exported point cloud and compared it with the terrestrial laserscanner one I observed an error on Z-value till about 50cm...
It seems too high according with what I have obtained in Photoscan...
why this?
Thanks for future replies and
Merry Christmas to all.
David

George

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Re: Accuracy (round N)
« Reply #25 on: January 09, 2013, 02:08:49 AM »
David hi,
if you have an error of 50 cm but it is more or less evenly distributed at the most of a DEM than I think it's just the matter of correction at GIS software. More odd when the delta varies in the range between -2 m and +2 m and absolutely unevenly.

I remember that recently you dwelled on comparision between LIDAR and PS for a castle roof. As far as I remember  you reported (finally) good results +- 20 cm.
What did you do there to improve results?

I, personally, do not experience the problem at the sites like e.g. fields but when it comes to a more complex areas, e.g. densely forested areas, my models get distorted mostly at the edges and at different spots inside the model (randomly). To a degree I account it for GCPs placement, which is not an easy task in the forest (vegetation issues etc. - i.e. it's hard to find a bare or true ground level).
On the other hand, I have also noticed a problem that PS sometimes doesn't reconstruct individual (or groups of individual) trees, which is also a pain and may cause additional problems.

Have you resolved your problems with model distortion.
George

P.S. Btw, what a UAV do you have?

George

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Re: Accuracy (round N)
« Reply #26 on: January 11, 2013, 05:58:33 PM »
Here are the final results ...
1. Aerial image
2. DEM minus DTM (by National Land Survey)
3. Precision is satisfactoryat the most of the model - in the range of + - 10 to 20 cm
4. The colours legend is on the DEM

George

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Re: Accuracy (round N)
« Reply #27 on: January 11, 2013, 06:08:58 PM »
DEM
The most important colour is green and its variations, little bit yellow and finally orange - the error is just 5 to 20 cm.
Other colours represent sort of natural situation at the site i.e. forest, other vegetation, objects etc.
« Last Edit: January 11, 2013, 07:23:03 PM by George »

Oli63

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Re: Accuracy (round N)
« Reply #28 on: January 14, 2013, 01:48:18 AM »
George, what software did you use to create the jpg from the last post (out of the Geo-tiff I guess)?
GeoSpy Aerial Imaging & Mapping GmbH
www.geospy.at

George

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Re: Accuracy (round N)
« Reply #29 on: January 14, 2013, 09:23:10 AM »
Hi Oli63
it is a screenshot from ArcMap simply processed in Paint
Actually, the raster you see is the result of mathematical operation ("minus") between DSM and DTM.
I just gave some colour (classified the resulting raster) to visualize the difference in error with pace of 5 cm.
GR
« Last Edit: January 14, 2013, 09:25:41 AM by George »