Topic: possibly a dumb question about points

[ronjonp]

So are X Y coordinates in a DWG the same as Northing and Easting coords? I recently got a table from a client that listed them both and the Northing and Easting numbers differ.

Please don't laugh at me 

Ron

[Lin-Z]

X,Y coordinates generally mean from ACAD's basepoint like 0,0.  Northing, Easting takes into account a particular coordinate zone. 

[Guest]

So are X Y coordinates in a DWG the same as Northing and Easting coords?

In a perfect world, yes (if the drawing is set up right).  I assume it's a "civil" site plan and not an "architectural" site plan?

[ronjonp]

Yes it is a civil site plan......have no clue who set it up.

[Dinosaur]

How different are the numbers?

[ronjonp]

You know Dino....I can't remember which drawing it was  What spurred the question was another project I was working on earlier this week where I was calling out northing and easting points. Apparently the base files we got were from a survey company so I'd assume the info is correct. Knocks on wood ever so gently.....

[Dinosaur]

Lin-Z's suggestion about a local coordinate system being displayed along with a grid based one seems to be the most probable, especially if the differences were large.  This might also happen because because there are certain features tied to a particular system that does not agree with the primary system but still must be referenced.  Unlikely, but if only slight, there may be a scale factor thrown in on one.

[Guest]

One thing to keep in mind: The AutoCAD x & y coordinates may be opposite that of the northing & easting.  When I run the Inquiry -> North/East command in Land Desktop, this is what I get.  Note that the X coordinate is the easting and the Y coordinate is the northing.

Select point:
AutoCAD's X = 586716.3952       Y = 259052.5088
   Northing = 259052.5088 Easting = 586716.3952

[ronjonp]

I assume too if the view was twisted and not accounted for it would give wrong numbers?

[Dinosaur]

I assume too if the view was twisted and not accounted for it would give wrong numbers?

If they used dview TWist, it should not matter.  The coord system remains intact and bearings list true.

[Guest]

Is your UCS set to World?  That would throw it off.

[ronjonp]

I assume too if the view was twisted and not accounted for it would give wrong numbers?

If they used dview TWist, it should not matter.  The coord system remains intact and bearings list true.

What about if you Dview twist and set UCS to view?

[Dinosaur]

Then everything is fubar in that viewport until you set the ucs to world.  The model itself should still be true.

[sinc]

One thing to keep in mind: The AutoCAD x & y coordinates may be opposite that of the northing & easting.  When I run the Inquiry -> North/East command in Land Desktop, this is what I get.  Note that the X coordinate is the easting and the Y coordinate is the northing.

That may not be the case, either, at least in Land Desktop.

The NE grid and the XY view are two completely different things.  If you use the Drawing Orientation feature of Land Desktop, you can move/rotate the NE grid in your drawing without affecting anything else.  However, this means that the XY you see may have absolutely no bearing on the NE.

In Land Desktop, if you want NE, you should NEVER use the XY.  There is actually an "ID Northing/Easting" command, which is what you should use (I have mine assigned to CTRL+I so it's easy to access).

The whole reason behind it is a whole series of problems with the way text, dimensions, leaders, et al. are handled in Autocad+LDD.  The only way to avoid all problems with text and labels is to avoid using DView TWist and use Drawing Orientation instead.  This has ramifications for INSERT and XREF, however...

This is probably another good topic for an article.  Essentially, Autodesk has made a terrible mess of the whole thing, so it takes a long article to explain all the issues, procedures, and caveats...  (thanks again, Autodesk!)

Since all labelling is handled in a completely different manner in Civil-3D, this doesn't really apply to C3D.

[Dent Cermak]

Remember back to high school algebra when you plotted formulas and sine waves, etc? Remember the X,Y grid. Same stuff. Remember the "Y" grid lines increased in value to the north and the "X" values increased  to the east? Thus x,y,z, coordinated are Easting, Northing, Elevations. You can bring in points into Auticad as x,y,z or use the state plane coordinates as n,e,z or as on the list PNEZD.
Want to rotate all that to fit your sheet without destroying the coordinate values? There is a lisp routine here called "Planview" that allows you to rotate your data to a sheet outline and resets tour crosshairs to parrallel the south neat line. A VERY hany routine indeed.
In the civil worle we work with latatude, longitude, state plane coordinates and local coordinate systems. EVERYTHING is base on coordinate geometry. It's all really simple once you get used to it.

[sinc]

OK, here's a synopsis of the XYZ and NEZ, DView TWist and UCS, and Drawing Orientation in Land Desktop.

[ronjonp]

OK, here's a synopsis of the XYZ and NEZ, DView TWist and UCS, and Drawing Orientation in Land Desktop.

Thanks for the article.