Reverse Z-coordinate

[fglatzel]

Civil 3D uses the right-hand rule, but the South African survey system (LO-31) uses the left-hand rule to create coordinates. Is there a way to reverse the Z-coordinate so it points down irrespective of the X-Y plan and set this to WORLD UCS. What objects need to be modified in order to reverse the positive Z-direction?

[Anonymous]

No, there is no way to use a left handed coordinate system inside of
AutoCAD.

Regards,

Peter Funk
Autodesk, Inc.

[Anonymous]

This possibility is essencial to use Civil 3D on Hydrographic work, because according to INTERNATIONAL HYDROGRAPHIC ORGANIZATION, the positive Z values must be about depth, keeping the same X and Y ways of WCS.

Any suggestion, or any future add-on to be able to do that?

Thanks

[codee]

Setting the UCS "z" axis does not work to solve this?

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[rl_jackson]

I read this and looked at the South Africa coordinate system, and I believe what you may be looking for is a way to set the drawing up as a SOUTH AZIMUTH vs. a NORTH AZIMUTH. I believe this can be achieved, I'm not at a PC at the moment but I believe its in the drawing settings, and is also in the settings of the survey database. I'll follow up on this when I'm in front of C3D

[codee]

YOU CAN ALSO SET YOUR "NORTH" DIRECTION IN THE "GEOLOCATE FROM MAP".

[Anonymous]

It doesn't work because changes automaticaly the X-axis to the reverse way, it follows only the rule of right-hand:

https://knowledge.autodesk.com/support/autocad/learn-explore/caas/CloudHelp/cloudhelp/2016/ENU/AutoC...

The North Azimuth has to be on the right and same way because all hydrographic clipboards drawings are to be joinable to any other all over the world.

The IHO has imposed that since ever. The Hydrographic official rules has a little difference of "Topographic" rules. 

Otherwise, AutoCAD is unusable to the Hydrographic work, only because it doesn't allow to define the 3 axis as we need, just only 2, as far I know.

[codee]

If the following will not work 

1. Right-click the UCS icon, and click Z Axis.
2. Specify a point for the new origin (0,0,0).
3. Specify a point that lies on the positive Z axis.

You could make your entire model and then turn it into a block with insertion at 0,0,0and then change the z scale of the block to -1

[Anonymous]

Thanks for your suggestions.

The second you give solves the problem to some 3D objects (on revolution solids and and 3Dpolylines).

However, to land surface, feature Lines, pointCloud and point list does not (etc.) without exploding, and that's not an option to the Hydrographic work.

About the suggestion of UCS Z comand, yes it changes the Z-way. However it imposes a reverse way to X-axis.  And the Hydrographic survey cannot work in this model.

A question: is there any possibility to apply a transformation matrix on UCS like that ?

[1,0,0

 0,1,0

 0,0,-1]