Topics

1

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

2

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

3

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

4

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

5

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

6

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

7

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

8

General / "cannot transform coordinates" error

« on: August 02, 2017, 11:27:38 AM »

Hi everyone,

I used the “local coordinate” as a coordinate system for my model. Then, in order to generate the DEM model, in the “planar projection” tab, I used markers to get the projection plane. The DEM seems logical but I did not get reasonable results when I am plotting shapes like polyline profile and ended up with the error of “cannot transform coordinates”.
What is the exact problem!

Best
Mina

9

General / DEM orientation problem

« on: July 26, 2017, 03:17:59 PM »

Hello,

I have a question regarding the DEM orientation. Since I have scaled the model, I got an arbitrary orientated model (attached photo1). In order to measure the DEM- based volume of a box, I need to have a DEM model projected in xy plane. I know that using the Object Rotation tool, I can manually rotate the model before building the DEM model into the desired view (attached photo2). How I can make sure that the obtained DEM model is really horizontal and not rotated related to one of the axes? Manually rotation does not make me sure the model is correctly oriented before building the DEM model!

Thanks
Mina

10

General / Errors of calibrated parameters

« on: July 14, 2017, 12:26:47 PM »

Dear all,

Sorry if I interrupt you with a repetitive question posted in Lens Forum.

Since I was not completely satisfied with autocalibration results of PhotoScan, as I did not clearly understand, how its algorithm works, I have decided to calibrate the camera beforehand using the Agisoft Lens.

Here is the results of my initial trial; but I did not know how to interpret the plots of radial and tangential distortion? If the displayed errors of calibrated parameters are low, it means that the calibration results are satisfactory?

any comments would be great. Thank you!

Mina

11

Camera Calibration / Errors of calibrated parameters

« on: July 11, 2017, 12:12:09 PM »

Hello everyone,

Since I was not completely satisfied with autocalibration results of PhotoScan, as I did not clearly understand, how its algorithm works, I have decided to calibrate the camera beforehand using the Agisoft Lens.
Here is the results of my initial trial; but I did not know how to interpret the plots of radial and tangential distortion? If the displayed errors of calibrated parameters are low, it means that the calibration results are satisfactory?

any comments would be great. Thank you!

Mina

12

General / analysis of two chunks

« on: May 15, 2017, 02:42:18 PM »

Dear all,

I want to measure the volume of the excavated hole. I have two sets of photos before and after excavation (as an example two photos attached). I modeled both sets of the photos in two different chunks and used the markers as a reference in the first chunk to align the second chunk. Is there any solution to subtract the area inside the frame in the first chunk from the second chunk to obtain the volume of the hole?

Thanks!
Mina

13

General / Camera calibration_Lens or PhotoScan

« on: May 09, 2017, 05:44:46 PM »

Dear all,

Do I need to use Agisoft Lens to get the camera calibration parameters before using the PhotoScan?
I did not understand how PhotoScan deals with camera calibration without using a pattern!
Thanks

Mina

14

General / Volume measurement accuracy

« on: April 10, 2017, 06:27:27 PM »

Hi,

I want to measure the volume of a box. I repeated the photography several times and simulated the model each time, but none of them met a volume error less than 1%.

I followed all the required simulated steps. The only unclear point to me is the effect of optimization procedure on the results. I have two models with same set of the photos, before and after optimization. Since the model files are too big, I could not attach them here.

The georeferencing and reprojection errors look reasonable. Why I could not get a high accurate volume? How can I interpret the results of optimization? In addition, how can I find out that the internal camera parameters have changed in a reasonable range after optimization?
Thanks you for your guidance.

Best,
Mina

15

General / distortion plot

« on: April 10, 2017, 12:03:50 PM »

Dear all,

I do not know how to interpret the distortion and residual plots. I have attached two images before and after first optimization. According to the first image, do I need to do optimization given that I want to do volume measurement at the end? How is the result after optimization? Do I need to repeat it several times?

Thanks for your help.
Mina