Forum

Author Topic: Local to projected coordinate system of point cloud  (Read 17221 times)

kgrover

  • Jr. Member
  • **
  • Posts: 50
    • View Profile
Local to projected coordinate system of point cloud
« on: July 20, 2023, 12:58:19 AM »
I have some existing point clouds as las / laz that I have imported into Agisoft, and imported as a local coordinate system (as we weren't sure of the source initially). I also have a CSV of control that was imported (as local), and they match to my point cloud.

But now I want to assign the projection of the point cloud (but not actually tranform the dataset) to a UTM Zone that we use, but when changing the Coordinate System in the reference settings to UTM (or really any chosen projection), it seems to be okay for the Control and just changes XYZ to NEElev, but is completely transforms the point cloud to a different location.

Is there a step missing to do this as other software does??

kgrover

  • Jr. Member
  • **
  • Posts: 50
    • View Profile
Re: Local to projected coordinate system of point cloud
« Reply #1 on: August 30, 2024, 02:17:29 AM »
I wanted to bump this question if anyone has the answer?

olihar

  • Sr. Member
  • ****
  • Posts: 278
    • View Profile
Re: Local to projected coordinate system of point cloud
« Reply #2 on: September 09, 2024, 10:52:55 PM »
Would this not be normal as you are assigning the data to a coordinate space. What would you expect to happen?

kgrover

  • Jr. Member
  • **
  • Posts: 50
    • View Profile
Re: Local to projected coordinate system of point cloud
« Reply #3 on: September 10, 2024, 04:47:23 PM »
The issue I have is that I don't want to it to transform the coordinates, but essentially just force the new projection for the data. As I said in this case, I had imported a dataset and had it initially set as local, but I wanted it to be redefined as UTM (but it is already in UTM coordinates) but keep the same N, E, Elev values.

BenW22

  • Jr. Member
  • **
  • Posts: 72
    • View Profile
Re: Local to projected coordinate system of point cloud
« Reply #4 on: September 14, 2024, 02:11:32 AM »
Hi,

I think this is a really good question. Something that seems simple but can be confusing as to how to make this work in Metashape. I would like to know the answer as well, so if anyone could provide that it would be great.
I havent tried this but if the data is already in a UTM and you create a new Metashape project maybe the steps are -
1. Create new metashape project
2. Open Reference Settings (after clicking the Reference Tab). Under the Coordinate System setting choose the correct UTM (if it is the list or you may have to create the coordinate system)
3. Import data

But I'm guess Kgrover has already tried this and is experiencing the problems he describes.

Any suggestions welcome

kgrover

  • Jr. Member
  • **
  • Posts: 50
    • View Profile
Re: Local to projected coordinate system of point cloud
« Reply #5 on: September 16, 2024, 04:58:31 PM »
Hey Ben. The workflow you suggest does work if you know and set the coordinate system info right off the bat in a project, but often times the coordinate information isn't known with some datasets immediately, etc.

However, maybe the issue is really even what "local" means in Agisoft. To me as a surveyor, local means whatever the heck I want it to be on a project (assumed 5000,5000 point, truncate UTM values, or to match building gridlines, etc.). However, I am not sure this is what it even means in Agisoft, but to me it makes sense it should.

BenW22

  • Jr. Member
  • **
  • Posts: 72
    • View Profile
Re: Local to projected coordinate system of point cloud
« Reply #6 on: September 18, 2024, 04:16:28 AM »
Hey K,

Yep we use the term Assumed coordinates for when we have no connection to a known coordinate system. I have also thought in Metashape Local = Assumed

kgrover

  • Jr. Member
  • **
  • Posts: 50
    • View Profile
Re: Local to projected coordinate system of point cloud
« Reply #7 on: September 18, 2024, 06:08:37 PM »
So I think I may have found the issue, but sure how to resolve.

With just an imported point cloud in a chunk and I change the reference coordinates between say UTM and Local,  the region bounds is what seems to get confused. I found in some other posts that the region is defined by the sparse cloud or even by the image locations, however, with just an imported point cloud I have neither of these.

I set some markers manually in the chunk (keying in values) and can zoom to those points, but the region is somewhere far gone from there. And if I reset the region, it says "unsupported datum transformation".

Is there a way to reset the region to my current view, or from the markers directly, etc.?

BenW22

  • Jr. Member
  • **
  • Posts: 72
    • View Profile
Re: Local to projected coordinate system of point cloud
« Reply #8 on: November 14, 2024, 01:51:03 AM »
Hey K,
Did you ever find a solution to this?

kgrover

  • Jr. Member
  • **
  • Posts: 50
    • View Profile
Re: Local to projected coordinate system of point cloud
« Reply #9 on: November 14, 2024, 05:33:47 PM »
Hi Ben. No, I was never able to resolve this yet.

BenW22

  • Jr. Member
  • **
  • Posts: 72
    • View Profile
Re: Local to projected coordinate system of point cloud
« Reply #10 on: November 15, 2024, 05:11:58 AM »
Hi K,

I have just spent hours trying to do something similar (but different) and have got it to work. I thought I'd share it with you in the hope it may work for you. I'm sure a lot of MS users reading this will think this is obvious or have a better way. I would be very happy to hear from those users.


Your MS job has the Reference Settings set as "Local Co-ordinates" but you later find out your data (including Marker data) is actually on a known Coordinate System and you just want to change the Coordinate System setting of your job to the correct CRS in the Reference Settings. So, you are not actually shifting the data in space, only re-assigning the data to the correct CRS name in MS -
note - this assumes you have your markers in a coordinate file, e.g. csv or txt format -
1. Your MS job is currently defined as "local coordinates" in the Reference Settings.
2. Using the "Import Reference" command - Re-import your markers (using the same csv or txt file you originally used to import your markers) - When the "Import csv" dialogue box opens, change the "Coordinate System" from Local Coordinates to the defined CRS you need. In the example I have attached I am going from Local Coordinates to MGA 2020 (EPSG 7856), click OK and import the data.
3. Under the Reference Settings the "Coordinate System" should now be showing the CRS you want (not Local Coordinates). But in the Model viewer your data should not have moved.
4. In the Reference Tab / "View Source" list - your markers should have the correct Labels (e.g. E,N,Altitude or Lat,Long  not XYZ)
5. The data should be in exactly the same place but, if needed, click the "Update Transform" button

Kind Regards,
Ben

kgrover

  • Jr. Member
  • **
  • Posts: 50
    • View Profile
Re: Local to projected coordinate system of point cloud
« Reply #11 on: November 15, 2024, 06:09:09 PM »
Hi Ben. I really appreciate you looking into this for me, but it still doesn't seem to work for me.

I can import the csv markers fine and select the actual coordinate system (in the case UTM Zone 11), and it does change the coordinate system in the reference page and the markers import in the correction location (with the background globe view).

But the initial point cloud is still not visible at all, and if I have the "unlock transform" set it gives me the error of "unsupported datum transformation". Also, the initial dense cloud still has "local" set in the metadata for the scan itself.

I tried playing around a few different ways with it, but still no dice for me.