# Processing, merging & replacing subregions

**URL:** <https://community.pix4d.com/t/processing-merging-replacing-subregions/18994>\
**Category:** PIX4Dmapper\
**Created:** [July 15, 2021, 2:33pm UTC](https://community.pix4d.com/t/processing-merging-replacing-subregions/18994 "2021-07-15T14:33:27Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![till](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/till/32/3151_2.png) [@till](https://community.pix4d.com/u/till)\
**Post date:** [July 15, 2021, 2:33pm UTC](https://community.pix4d.com/t/processing-merging-replacing-subregions/18994/1 "2021-07-15T14:33:27Z")

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Hi there,

I’m working on a large project (ca. 5.000 imgs) that is largely optimized. I.e. a lot of MTPs as well as GCPs have been added. However, there is one area that cannot be optimized. There is a tilt/shift in the generated ATP like seen here: [Vertical Shift between Flight Blocks](https://community.pix4d.com/t/vertical-shift-between-flight-blocks/6219).  
I would like to try to process this sub-area again. Since p4d does not offer the possibility to calculate a sub-region in Step 1. Initial Processing, I will have to calculate a new project with selected images (or did I miss something?). I will insert the MTPs / GCPs from the project that has already been calculated there. (I already know that there will be no tilts with other calculation settings). If I want to merge the projects afterwards, the tilt from the old ATP point cloud will be most likely retained. How can I completely replace this area with the new one? A recalculation of the old large sub-region is actually out of the question for reasons of time.

Kind regards

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**Author:** ![Yuka](https://avatars.discourse-cdn.com/v4/letter/y/9d8465/32.png) [@Yuka](https://community.pix4d.com/u/Yuka)\
**Post date:** [July 16, 2021, 5:02am UTC](https://community.pix4d.com/t/processing-merging-replacing-subregions/18994/2 "2021-07-16T05:02:59Z")

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If I understand you correctly, you should be able to replace it with the new one if you merge the results of A and B:

A: Process images without the images of the sub-area  
B: Process with images of the sub-area

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**Author:** ![till](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/till/32/3151_2.png) [@till](https://community.pix4d.com/u/till)\
**Post date:** [July 16, 2021, 7:00am UTC](https://community.pix4d.com/t/processing-merging-replacing-subregions/18994/3 "2021-07-16T07:00:41Z")

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Hi Yuka, thanks for the reply.  
That’s not exactly what I asked for.

I already processed A and B in one project - lets say AB. I’am reprocessing sub-area B now and would like to merge it to the existing AB project but reject the false B sub-area from the AB project. As I already said reprocessing A would be the worst for reasons of time.

Is it possible to edit (clip) the Automatic Tie Points files (result\_tracks2/3\_full\_1.las) by polygon and delete the false sub-area B?

Thanks

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**Author:** ![Yuka](https://avatars.discourse-cdn.com/v4/letter/y/9d8465/32.png) [@Yuka](https://community.pix4d.com/u/Yuka)\
**Post date:** [July 16, 2021, 8:30am UTC](https://community.pix4d.com/t/processing-merging-replacing-subregions/18994/4 "2021-07-16T08:30:29Z")

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Thank you for the explanation. I am afraid to say that Automatic Tie Points (ATPs) cannot be edited. ATPs are generated from the key points that are automatically detected in the images; thus, they will be difficult to delete. Apologize for the inconvenience.