Understanding Geographic Location

[cattjake]

I am not grasping the concept of geographic location, could someone explain its implications?

Specificly, how does a defined geo location impact a drawing that has drawing settings defined corrdinate systems?

How does information behave when bringing it from drawing A (with a defined corrdinate system and geo location) into drawing B (same corrdinate system but no geo location)?

How does the geo location impact the mapimport of shapefiles from a known corrdinate system?

[ericcollins6932]

A geographic location is a coordinate pair or coordinate triplet with some origin that typically attempts to describe your position on earth.

Generally it can be in form of x,y,z or latitude, longitude, and h.

To properly georeference a drawing, one should define a coordinate system for that drawing so that it can be referenced to the real world; otherwise it is simply a local coordinate system.

If drawing A and B share the same coordinate system but one of them is not defined, ArcGIS at the least, assumes they are the same. If they are, great. If not, one introduces issues.

In order to mapimport properly, one needs to know both the origin and destination coordinate systems to ensure a proper transformation. If importing shapefiles with a known coordinate system (that is defined in C3D), ensure your destination dwg is properly set to the desired coordinate system in which you are working and that the imported coordinate system is set correctly. The transformation engine then should theoretically import your shapefiles seamlessly.

[cattjake]

Thanks for the response.

If you have a drawing set to a known coordinate system, why must you also set the geographic location? Shouldn't the referenced coordinate system and your x,y,z within it place you in the correct location in the real world?

[ericcollins6932]

I've never had to set my geographic location C3D to the best of my recollection. AutoCAD, yes. AutoCAD does not understand coordinate systems, only Map 3D and higher have that functionality.

[cattjake]

I also have never put a geo location into any of my drawings. But I received a C3D drawing from a surveyor with a geographic location. I am trying to understand how I need to take this into account when I incorporate the information with the geo location into all my construction drawings, which do NOT have a geo location.

[n2itive]

Personally, I would just ignore the Geographic Location.  We had issues within our 2012 & 2013 template files which the geographic location would flip every time you opened the template.  From that point on I was told by autodesk to ignore it and turn off the view cube which is tied to the geographic location.  I was also told it has NO ties to the drawing coordinate system.  I was skeptical but haven't had any issues. Just my 2 cents.

[cattjake]

Can anyone confirm there is NO ties between corrdinate systems and geo location?

[n2itive]

If you search for "view cube" or "geographic location" you'll get a bunch of results. Here's a link that explains it a little more, but isn't from Autodesk. http://totalcad.wordpress.com/2011/03/10/follow-up-on-feeling-a-little-skewed/

Keep in mind most of these are for versions older than 2014. Maybe things have changed but back then the Geographic location was said to be only tied to importing Google Earth images.  I will note that if you remove the geographic location, as shown in the link above, there have been some users who said their coordinate system was reset to a generic one automatically. I experienced this on a few occasions in which case I had to reset my drawing coordinate system after removing the geographic location.  That is why I say just ignore it all together. Don't remove it, don't change it, just ignore it :).

[Murph_Map]

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@cattjake wrote:
I also have never put a geo location into any of my drawings. But I received a C3D drawing from a surveyor with a geographic location. I am trying to understand how I need to take this into account when I incorporate the information with the geo location into all my construction drawings, which do NOT have a geo location.

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The Geo Location is for users not using Civ 3D or Map 3D. The survor make of used it if they pass the dwg on to others (Architectural firm) or the survey may not be using a civ application and just AutoCAD. The intent was to allow those non-civil users a way to plot their dwgs on Google Earth or another coordinate defined map with out having to move, scale, rotate etc. 

[HansSMS]

The geo location affects the display of the view cube: This is buggy in Civil 3D 2013. Sometimes the view cub diplays at a random odd angle, I just remove the geo location, and the view cube then displays correctly. This action has never removed my transformation settings.