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Messages - Ron

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General / Re: Model upside down and tilted
« on: July 31, 2014, 03:19:51 AM »
Hi Jailbazers,

I get the same problem when I use camera positions without co-ordinates. My method is to do as Alexey suggests and in addition uncheck the cameras (Markers checked), then align photos. This gives camera positions based on the ground control co-ordinates. This works fine for small projects (<100 images). Haven't tried this on large projects.



Hi Andy,

Thank you for the reference to those papers.

Though there may be good consistency between lenses in the manufacturing process, I would calibrate each lens individually. The consistency of systematic errors across the lens especially towards the edge is a good thing as it allows software like agisoft lens to predict the lens distortion  with good result using consumer grade cameras. I think the papers are dealing mainly with k1 values, we have moved forward since 2007.

For further reading, a recent paper, is worth looking at as it deals with methods of reducing the domed distortion and possibly (hopefully) a reduction of the number of ground control points.

Mike R. James and Stuart Robson 2014 Mitigating systematic error in topographic models derived from UAV and ground-based image networks, Letters to ESEX, EARTH SURFACE PROCESSES AND LANDFORMS

Hi All,

I have been following this forum for a while now and wanted to say that my knowledge of PS has vastly expanded due to member input. So I wanted to say thank you for your time and effort for myself and for all those others that read this forum but may not necessarily comment.  :) :)

Hi Andy,

Thank you for your comments.
Actually I have been importing calibration, fixing it, then aligning, then entering GCP, then optimizing.
I plan to update my procedure manual as suggested.

I will be looking into your other comments too.

Hi Andyroo,

I can give you what I know from my very limited knowledge of Photogrammetry and Structure from motion. Hopefully someone can correct me if I am wrong.

1. I believe that the "fixed Calibration" check box is for Metric Cameras rather than domestic grade cameras.

2. When optimizing checking the Fit scew and fit k4 boxes allows PS to calculate individual values for scew, k4,p1 and p2 for each . I have seen different matrices for the "Camera Calibration Matrix" so I don't really know how the values for scew, k1, p1 and p2 affect the final point cloud however, I do end up with different error values for my markers.

3. I don't know what you mean by changing the camera model.

4. I assume you align photos, import calibration and then split image groups. The next steps I usually take are place ground control markers and Align Photos. This seems to give me the best result.

5. As regards aligning photos I find that any changes I make regarding the position of markers say requires a redo of align photos. My method these days is to align photos at low setting, place markers, add calibration,  uncheck cameras, align photos at high. Optimizing alone does not seem to be enough. My results generally improve by doing this especially when my cameras do not have rough GPS co-ords.

General / Re: model lower than ground control
« on: June 26, 2014, 02:19:43 PM »
I'm not sure about your case but when I have similar problems I find I need to make adjustments to  my weightings. I spend quite a bit of time here making sure my ground control is satisfactory before forming the dense cloud.

Go to the Ground Control Settings dialog box in the Ground Control Pane to adjust your weighting.

 I uncheck camera positions and rely on ground control. All ground control points should be checked.

Then optimise. Note that when you optimise you will loose your dense cloud.

My typical settings are 10m, 0.005m, 0.005m 1pix, 2pix. Note that on the last option Agisoft recommends leaving this at 4pix.
This should give you a + and - range for your errors.
If errors remain large also check for errors in each ground control points.

General / Re: Ground Control Points and their use
« on: June 23, 2014, 02:01:54 PM »
Scale bars work as well. I use a surveyors staff for this and works fine. You can also measure distances between points on your wall, create targets in PS at these points.
Create a scale bar from target pairs. Enter known distance.
Leave the targets unchecked in PS.
Have the scale bar checked.
Good luck

Hi Morgan, another thing to look at is image stabilization. This should be switched off. Image stabilization tends to alter the focal length giving inconsistent results.

Feature Requests / Generate Report command
« on: May 13, 2014, 02:33:02 AM »
When using Edit>Generate Report the command assumes a top down view. Can an option be added for "Current View"?

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