global shift and data coordinates

[db_chicago]

Hello All,

I have a question about the import/export process for geographic data. I am working with a LAS file that has the following datum and coordinate system:
Horizontal Datum: NAD 83 (2011)
Coordinate System: UTM Zone 15

When I import the data into CC I have translated/scaled the entity. When I export the data from CC and import it into a CAD file with the correct datum and and coordinate system, the data is not in the correct geographic location. Am I missing a key step in the process? Do I need to manually enter the shift values? I had assumed that the values in the shift fields were being pulled from the file that I am importing.

I apologize for my questions being vague. I'm a new user of CC and I'm just trying to understand the import/export process for data with geographic coordinates. I'd appreciate any guidance regarding the steps in this workflow.

Thanks,

Dave

[daniel]

With which tool have you scaled the entity? If it's 'Edit > Multiply/scale', have you left the 'Recale Global Shift' option checked? (cause this will probably mess the global coordinates).

And more generally, rescaling is always tricky, unless you do it when the points are properly 'centered' on the scale origin (so that the global coordinates of this center are maintained). Otherwise the scale implicitly take place at the local origin (which depends on the Global Shift you applied at loading time).

[db_chicago]

Hi Daniel,

Its the Global shift/scale dialogue box that appears when opening a LAS file. Yes, I had left the "Rescale Global Shift" box checked.

[db_chicago]

Hi Daniel,

I'm still not clear on what the recommended procedure is for importing/exporting georectified data so that it retains its real world coordinates. I'm hoping you can set me straight. My workflow is: import LAS file, subsample/extract ground surface points, export as CSV file, import the data into a georectified CAD file, and create a DTM. The horizontal datum for the LAS data is NAD 83 (2011) and the coordinate system is UTM zone 15 (the CAD file as the same georeferencing). The export from CC needs to have the correct coordinates so that it aligns with other geographic data.

I am unclear on how the Global shift/scale dialogue box should be used for geographic data. If you have any guidance on how I can import data from CC so that it is in the correct geographic location I would be very grateful.

And as a side note. Thank you to you and all of the other contributors who have developed CC. I feel that it has opened up an entirely new world for me. Thank you.

[daniel]

By default you shouldn't change anything in the 'Global Shift' dialog and simply apply the suggested shift. The original coordinates will be restored when you'll save the cloud to a new file.

The only reason why you would have to change something is when the default 'LAS shift' (that is used as suggested global shift when loading a LAS file) doesn't make the coordinates small enough. In this case, you can tweak the X, Y (and maybe Z) components of the global shift.

But don't play with the global scale.