Messages

1

General / Comparison chunks according the capacity: two chunks and merged chunk

« on: April 12, 2021, 09:00:15 AM »

Good morning,

A few weeks ago, I posted the same question, but the answer was not posted, so I am posting it again. Sorry.
The question is again (more specifically) as follows.

Below:
I have one set of image data shot with UAV and one set of image data shot with DSLR.
Both datasets took the same subject.
When creating a dense point cloud for the subject from these two datasets, I used two methods.
One is UAV data set and DSLR data set in one chunk, the other is UAV data set and DSLR in different chunks to create a dense point cloud, and then the chunks are merged.

As I expected, the capacity of the final two dense point clouds would be similar, but the difference was quite large.
When working with two datasets (UAV + DSLR) in one chunk, the capacity of the dense point cloud was about 6GB. The UAV data set and DSLR data set made into dense point cloud in different chunks were 7.6 GB (DSLR) and 1.7 GB (UAV), respectively, and the merged of these two chunks was 9 GB of dense cloud.
The parameters from Align to Build Dense point cloud are the same.
But rather, what is the reason that the capacity of the dense point cloud that worked with DSLR and UAV in one chunk is smaller than the capacity of the dense point cloud built with DSLR dataset (7.6GB)?

Wait for your answer. Thank you in advance.
bigoo.

2

General / different file size and the number of point cloud between two chunks

« on: March 15, 2021, 03:33:39 AM »

Hi,
I have a question about the number of dense points and file size.
When I surveyed the study area, area a was shot with full frame dslr and area b was shot with insprire x5.
Area a has a steep slope, occluded surfaces occurred during vertical shooting, so I photographed with dslr on the land, and area b is a flat and large area, so inspire x5 was used.
Area a and b are in the same space.

When building a dense cloud, I used two methods.
Scenario A: Modeling was performed by simultaneously inputting the shooting results for areas a and b.
Scenario B: After building a dense point cloud individually for the shooting results for area a and b, I merged the two chunks(area a and b).
By the way, the number of points in scenario A is 808,987,475 and the file size is 11.37 GB. The number of points in scenario B is 462,749,625 and file size is 6.79 GB.
I expected the results for scenarios A and B to be similar. However, the modeling results were almost twice as different as mentioned earlier.
What is the reason for this?
If it’s possible, I’d like to give my two reports.

3

General / What parameters should I choose when align?

« on: March 28, 2019, 03:53:47 AM »

I am using the Photoscan to build a DEM and map of the coastal area.
I shot about 1000 drones in the coastal area.
The align parameter is from highest to lowest.
If I set the parameter to the highest value, the number of key points should be the highest, and when it is set to the lowest, the number of key points should be the lowest.
If you look at the align result, the number of key points is as follows.

highest: 14,619
high: 106,024
medium: 476,958
low: 154,501
lowest: 29,701

When set to highest and high, only the pictures in some areas were matched.

The other parameters when align are:
Generic: no
Reference: yes
key point limit: 40,000
tie point limit: 4,000
adaptive camera model fitting: yes

What parameters should be set to produce the best dem and map in this case?

The drones used were the DJI Phantom 3 advanced, with an altitude of 100 m and an overlap of 80%.

4

General / Which Align mode I should use?

« on: June 13, 2016, 07:39:43 AM »

 Good day, I'm Jae Jin, Yu, South Korea.

I have made DEMs to write a paper using Phantom 3 pro and this software.

In order to make a DEM, I read the manual and did that.

According to the manual, if I had a photos that have a gps postions, I should have aligned with 'reference' mode.

However, when I aligned photos taken by Phantom 3  with 'reference' mode, I've got the 267,030 points and only 273 photos aligned.

Otherwise, when I aligned the photos with 'generic'  and 'disabled' mode,  I've got the 266,910 and 249,249 points and 270 and 297 aligned photos respectively.

then, I made DEMs  from aligned photos with 'reference' and 'disabled' mode.

As a result, I could get such higher accuracy DEM from disabled mode aligned.

This result made me very confused.

So, If I want to get higher and reasonable accuracy data, which align mode I will use?

Thanks in advance.

Jae Jin.