World origin

Hi,

When Importing Georeferenced DXF files into rhino, the geometry is placed at a specific point away from the world (I believe?)

I am wondering where the world origin is? Is it determined by where you choose in the ‘Sun’ rendering tab?
E.g., I set it to my current city location, then I import a DXF with data located in that city, it seems to be located in relation to where I set my location for the sun.

Is there anywhere I can learn more about the World Origin, and how it’s created/where it is etc.?

Regards,
Jeremy

This might be useful:

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Thanks John for that link.

I’m wondering if the world origin is the same as the Geolocation mentioned on that page?
And if so, can the Geolocation be set by using the EditAnchorPoint command?

Best,
Jeremy

Hi Jeremy -

The Rhino world origin is simply at 0,0,0 at all times. It doesn’t correspond to any position on Earth (or any other planet). When you import that DXF, Rhino just reads the coordinates that are in that file and it’s the creator of that dataset who decided where “zero” is located.
-wim

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As someone who is accustomed to navigation systems I thought that Earth origin is at sea level on the equator at a longitude that goes through a specific spot in Greenwich, England. Do civil engineers and surveyors have their own ideas, or assume the origin for their own convenience?

Yes, they do.
Here in the USA, each state has one or more “State Plane” Coordinate Systems. The Washington coordinate system of 1983 (NAD 83), north zone, is a Lambert conformal conic projection of the GRS 80 spheroid, having standard parallels at north latitudes 47° 30’ and 48° 44’, along which parallels the scale shall be exact. … This origin is given the coordinates : E = 500,000 meters and N = 0 meters

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Well, ask and learn. Thanks John.

My guess is if you ask the originator of the Georeferenced DXF file, they can tell you which State Plane coordinate system it is based on.
Then you’ll have your reference point basis.

Yep, each country/region has its own ‘zero’ point…

Thinking about it a bit more, doesn’t this have to do with depicting spots on the globe upon a flat piece of paper with a minimum of departure from exact scale? Today, with 3D models, I would assume that there is no need to involve projections. If we forget, for this topic, about maps, do the state/national standards also specify their own 3D “working” origins for the global coordinates?

Lat/Long is generally used for navagation and GPS.
Survey and engineering work is “simplified” to use a flat, XYZ regional coordinate system.

Another common practice is to designate a project coordinate “datum” or origin. The reason is computers only have 16 digit numbers. If you add 1,600,000 to X coordinates and 500,000 to Y coordinates to get them on the NAD 83 State Plane system, you don’t have enough digits left to avoid significant rounding errors.
This Datum point will generally be shown on the drawings together with the assumed State Plane coordinate translation.

Got it. Makes sense, I suppose, since everything is referenced to the gravity normal vector flat earth is the most convenient assumption.

A little farther down the rabbit hole…
Some old surveys in England and around here will give distances in Chains, Rods and Links, which are based on the old measuring tools they used back then.