Cloud to cloud distance

[Ioanna]

Hello!
This is my first time writing in a forum so excuse me if my writing style is a bit confusing.

I have a couple of questions regarding the çloud-to-cloud distance option:
1. I read that the scale unit is the same as the origin file. So if the origin file is in m, then the displayed distances after the comparison are in m too, right?
2. The distances that I get when I split x,y and z are in which axis? How do I get the z from that?
3. I have two strip that don't overlap 100% and the largest difference appears where there is only one strip. Is that difference the result of: strip coordinates-0??? And if yes, where is zero considered?

I am looking forward to hearing from you.

Thanks,
Ioanna

[daniel]

1. Yes
2. each 'component' is output in a different scalar field. Simply select the 'z' one. And we use the main X, Y and Z vectors of the default coordinate system
3. the C2C distance is the 'distance to the nearest neighbor', therefore there's always a 'neighbor', even though it may be very far. If you want more clever/robust distances, you should consider the M3C2 plugin.

[Ioanna]

Thank you very much for the fast response!

[Ioanna]

Hello, again!

I want to export the result of C2C distances. I tried the .cvc file after splitting in X, Y and Z but the values I get for Z in the file differ significantly from the ones displayed in the cloud according to the scalar. Why could that be? How can I fix it?

Also, I would like to export the result (cloud AND scalar) an an image. I tried the TIF file but it doesn't open: it's damaged or too big or not supported..Is there another way to do that?

Thank you!

[Ioanna]

And also, I get negative distances, although I read under another question that C2C always returns positive distances. Is that right?

[daniel]

1) What is the 'CVC' file? Do you mean a text/ASCII file?

In this case, try to save the 'columns title' as well (see the 'Save ASCII file' dialog). This way you'll be sure to look at the right column (you may mix it with another one). The scalar fields should be at the end (after the X Y Z coordinates, and potentially colors and normals).

2) To export the view as an image, you should use 'Display > Render to file' (with PNG or JPG extension typically). Otherwise you may be trying to save the cloud as a raster, which is not a standard TIFF image, but a 64 bits geo-tif file.

[Ioanna]

Dear Daniel,

1) I meant .csv file i.e. text file, I am sorry for the typo.
2) Thank you, that worked! Yes, I had saved the cloud as a raster that's why I couldn't open it.

Thanks a lot again!

[Ioanna]

Dear Daniel,

Yet another question came up related to C2C distance option.

After the run is complete, in the properties field appear meta data scales for x, y and z (since I split dimensions). Do those refer to the scale describing the difference between the two clouds (right side of the screen)? Or do they refer to the initial transformation of coordinates in cc?

Capture.JPG (115.03 KiB) Viewed 8893 times

[daniel]

Hum, are you sure it appears after the C2C distance computation? I don't recall any such thing. Isn't it the LAS scale maybe? (if the input cloud is LAS - in this case it's a parameter specific to LAS file and it has no particular meaning)

[emmaird@hotmail.com]

Referring to this: I compare two point clouds. after computation, I cannot find and display results... what is the next step after closing the dialog compute box?