Why is it "Selecting pairs..." when I only want to merge chunks?

[jenkinsm]

I'm trying to merge two large chunks into one and I thought it would be quick, but I'm surprised to see that it's going through the "Selecting pairs..." process which is taking a long time. Does anyone know why it's doing this? I didn't align the chunks, I'm just trying to merge them.

[Alexey Pasumansky]

Hello jenkinsm,

If you have selected Merge Tie Points option, then Metashape will try to find the correspondence between the tie points in each of the source chunks.

[AdSuwo]

Hello Alexey, jenkinsm, and other members....

I have experienced similar problem. I have executed chunks alignment process, for 2 chunks, with approximately 35% overlaps one to another, since 3 days ago but the process has not finished yet until today.
The first chunk contains 10,847 photos, 1 component, with 3,476,786 points (120,000/12,000) and the second one has 15,651 photos with 27,254,766 points (160,000/16,000). Both chunks showed excellent results, but still in tie points, because I want to merge both chunks with point based alignment.
Except KPL and TPL abovementioned, the other parameters are the same, which are: Highest accuracy, Generic preselection, Source, Adaptive camera, No mask, and No stationary

Batch process was employed to handle the chunks alignment, and the parameter was: Point based, Highest accuracy, KPL 160,000, No mask, and Generic preselection.
The first step, which was saving project run about 1 hour, the following steps or Detecting points took 1 days 16 hours, and the third or Selecting pairs as the next process has took 1 days 14 hours until now. So in total it has 3 days.

When I was watching the end phase of the Selecting pair process, this morning, actually, it has reached 100% within 1 days and 04 hours 17 minutes.

Meaning that the job has around 7 hours without changing to another processing steps. Because as an alignment chunks process, in total, when selecting pairs process finished, the "green-bar" indicator reached only around 50%.

The questions are:
1. After selecting pair process, how many steps are remained for this alignment chunks process?
2. Which steps require more or longer period of time?
3. Considering the case I have, do you have any suggestions? Should I abbort the operation or wait?

I have 2 options in my mind when abborting or cancelling this process:
1. Try another procedure of chunk alignment with camera based, or
2. Add more photos to the chunks having more photos, and run photo alignment with Keeping Key Point on the preference + without reset current alignment.
Since I aligned the photos of those both chunks without Keeping Key Points option checked (off) 2 weeks ago, it is okay if I turned on the preference now.... or should I realigned again both chunks from scratch before aligning them. It took abot 40 days for both chunks.

I hope someone who success or expert in doing chunks alignment and merging proceess would kindly share the tips and tricks. Your enlightenment would be highly appreciated.

Many thanks and regards,
AS

[AdSuwo]

Just want to add another information and queries:

1. For the recently chunks alignment process that has not finished yet, I do not checked "keep key point" in the preference tab, will it be the problem?
2. The remaining disk-space is 279 GB, I hope it will sufficient because I read in an article in this forum that unsufficient space may create problem as well.
3. Instead of aligning chunks with point or camera based option, can I employ append function as mentioned in the following article, but both chunks are still in tie points https://agisoft.freshdesk.com/support/solutions/articles/31000157701-manual-chunk-alignment-standard-edition-

Many thanks and regards,
AS