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Messages - Mina

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1
General / Re: markers error and volume simulation
« on: September 25, 2019, 06:55:37 PM »
Just redid calculations from high quality dense cloud and get:

0.077244 m3 (before) - 0.082583 m3 (after) = -0.005339‬ m3 = - 5.34 dm3 or -5..34 liters

quite different from medium quality...

Hi Paulo,

Thank you so much for your reply. I will check the procedure that you followed to model the two chunks. But worth to mention that, I have used another method in the field to measure the volume and it seems that it is much higher than 5.34 liters!
I don't know what is the exact source of error?

Best,Mina

2
General / markers error and volume simulation
« on: September 23, 2019, 11:15:04 AM »
Dear all,
I have asked this question before; however, I did not get any answer.
I have a model, including two chunks, named before and after. I want to subtract the area modeled in the middle of a frame located in both chunks to obtain the volume of the sampled soil. The model can be downloaded via: https://www.dropbox.com/s/mzpbyf3113fjzqj/sample17.7z?dl=0

Regarding the projection error of markers.
After detecting markers, I have noticed that the error of some markers is quite high, sometimes around 25 pix. I have checked their positions on all photos and it looks that they are located correctly. To reduce the error, I removed the markers on those photos that the error was high (based on information in Show Info). This worked but I lost the markers on those photos. Do you know what the reason is? Does it add extra errors?

The volume that I obtained:
Volume inside the polygon in “before” chunk: 0,859293 m3 (base plan: custom level 0.00m)
Volume inside the polygon in “after” chunk: 0,865352 m3 (base plan: custom level 0.00m)
The subtracted volume (0.0061 m3) is extremely lower than what I expected. I thought some mistakes might happen! Could you please check if the model was properly simulated?

Thanks
Mina

3
General / Re: marker projection error
« on: September 13, 2019, 09:13:40 AM »
it is in px.

4
General / marker projection error
« on: September 10, 2019, 08:52:15 PM »
Dear all,

I have a question regarding the projection error of markers.
After detecting markers, I have noticed that the error of some markers is quite high, sometimes around 25 pix. I have checked their positions on all photos and it looks that they are located correctly (as you can see in the attached picture for marker 20).
Do you know what is the reason?

To reduce the error, I removed the markers on those photos that the error was high (based on information in Show Info). This worked but I lost the markers on those photos. Does it add extra errors?

Thanks
Mina

5
General / Re: Volume measurement accuracy
« on: November 12, 2018, 05:12:12 PM »
Hi,

I have mainly used the following suggestions;

http://www.agisoft.com/forum/index.php?topic=9485.msg43931#msg43931

Best,
Mina

6
General / SEUW Value/k-p values
« on: August 24, 2018, 02:12:38 PM »
Hi everyone,

After each Optimization trial, you can find a value for the Standard Error of Unit Weight (SEUW) in the Console window. Can someone explain how this value should be changed during the optimization?
In my case, it stoped somewhere around:
adjusting: xxxxxxxxxxx- 0.306153 -> 0.305069

Thanks!

Best,
Mina

7
General / Optimization procedure
« on: August 21, 2018, 02:47:28 PM »
Dear all,

I have a question regarding the Optimization, which is done using the following steps:
1. Remove iteratively points with false matches and higher reprojection errors (10% of the total each time). My goal is to remove all points with the reprojection error higher than 1 pixel.
2. Optimization and repeat the step 1 again. Normally f, cx, cy, k1234, p12 should be fine for a digital camera. Other parameters adjust to zero in the camera calibration window and uncheck in the optimization window.

I got the object resolution of 0,38 mm during the photography. Is this limit of 1 pixel reprojection error  a correct choice?

How many iterations do I need? I know that trying too many iterations affect the reconstruction accuracy, am I right?

In one of the trial I repeated the whole procedure 4 times, but it seems that the maximum reprojection error didn’t drop to the desired value (1 pixel) and didn’t change too much in general (attached), what is the problem?

Thanks,
Mina


8
General / Re: Volume measurement steps
« on: August 01, 2018, 11:35:27 AM »
Mina,

I think the problem is with your local coordinate system.  I aligned the LCS according to targets 22, 19 and 24.

X axis target 22 -19
Y axis target 22 -24

and Z perpendicular to level of your square box.

From there DTM is generated and volume of hole can be correctly calculated….


Hope this helps,
Hi Paul,

Thanks for your reply. I have still some questions!

What is the problem with local coordinate system? I aligned both chunks based on the markers and then I have drawn the same polygon in before and after excavation models. The xyz coordinates of the polygon vertices (attached photo) show that the positions of the polygon in both models are the same, but I cannot understand what the problem is then!

Could you please explain how exactly you aligned the LCS according to targets 22, 19 and 24? Did you measure the xyz coordinates of these markers based on the Scale Bars distances?

Best,
Mina

9
General / Re: Volume measurement steps
« on: August 01, 2018, 11:33:34 AM »
Hello Mina,

And what value have you expected?
Hi Alexey,

Since I want to calculate another parameter based on this volume, the measured volume should be higher than the volume, I calculated so far. I don’t know, what is the problem?

Mina

10
General / Volume measurement steps
« on: July 24, 2018, 12:16:37 PM »
Dear all,

I have tried to measure the volume of a hole excavated in the middle of a frame. I modeled the surface before and after excavation. The calculated volume doesn’t look correct!
Volume of the hole =  0.007378 m3

Please find the project and analyzed photos from the following link; https://1drv.ms/u/s!Ar3Xxh0xFee96XrwKSq6Y4yfWpuj

Any suggestions will be appreciated. Have someone a better step by step procedure for volume measurement using PhotoScan?

Best,
Mina


11
General / indoors photography problem
« on: June 19, 2018, 10:47:22 PM »
Dear all,

I have a question regarding the camera setting. I have to take photos indoors where I don’t have enough light. I tried to increase the brightness using an artificial light above the area. It was getting a little bit better.

I used this camera setting (F4.5, ISO 320, and Shutter 1/40); however, I have still some problems with the focus of the camera. I used the manual focus and fixed it before photography. My photos are sometimes blur, which I do not know why!
Is the shutter speed big? Any suggestion would be great!

Thanks, Mina

12
General / Re: sample volume measurement
« on: April 19, 2018, 11:34:40 AM »
Hi :)

Thanks again for your suggestions.

Given that I didn’t have any 3D coordinates of targets (I couldn’t measure them indoors), scale bars errors are probably the only option to assess the accuracy of the model and the quality of the result. However, I agree that it cannot be enough and that was the reason for my first post to somehow improve the accuracy, if possible.

Regarding the camera calibration, once I tried to use Agisoft Lens, but I didn’t get consistent camera parameters for some trials, therefore, I preferred to trust the auto calibration results.

And for the last point, I am looking for around 1-2% of volume error which can increase significantly the accuracy of my further study.

Best,
Mina



13
General / Re: sample volume measurement
« on: April 13, 2018, 02:08:29 PM »
Hi,

Thank you for your detailed response.

Regarding the targets, the before/ after targets were not moved during photography.  Your suggestion is to compare the estimated targets coordinates with each other in different chunks, right? What do you mean by “registration accuracy”?

In fact, since I don’t know how the optimization algorithm works and which camera parameters should be checked or not (like what you mentioned, B2 in the last chunk), I didn’t use it during my simulation. In addition, sometimes there is no improvement and I cannot interpret it exactly why (as you mentioned, no improvement happened for the first chunk). In general, is it possible to interpret somehow the adjusted camera calibration parameters to assess the quality of alignment step?

Regarding you last point, if I change the photography method to take convergent images, the results would be improved? Is there any problem with my photography method (parallel and coplanar)?

Thanks again for your explanation.

Mina



14
General / sample volume measurement
« on: April 09, 2018, 05:13:57 PM »
Dear all,

I had three sediment boxes. I took a sample from each box. The idea was to measure the volume of sampling area in each box individually. For this purpose, the sediment surface was photographed with a camera with fixed focus before and after excavation.

The sediment surface in each box was simulated two times, before and after excavation and then the measured volumes were subtracted to calculate the sampling volume in each box.

All chunks were scaled using scale bar. Comparison of measured and simulated value for scale bars shows that the surface was accurately modeled in each chunk. You can find the project file here: https://1drv.ms/u/s!Ar3Xxh0xFee9xC9h8nXG0RSZu_LQ

I have still two questions to make sure that the model is working precisely:

1. Are the small scale-bar errors enough to conclude that each chunk was modeled accurately? or do I still need other criteria to check in terms of model accuracy?

2. Why the camera calibration parameters are different? Do I need to do optimization as well given that the scale bars errors are small right now?

Thank you for your feedbacks.

Mina

15
General / Re: "cannot transform coordinates" error
« on: October 18, 2017, 03:29:26 PM »
Hi Alexey,

Was this problem solved? using  markers as a planar projection discussed in previous comments. Can it be considered as a bug of the software?

Best,
Mina

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