Another Twist for World

I’d like to offer a few other arguments for the use of the DVIEW TWIST routines discussed in North Rotation: Using Twist Screen. The four Carlson DVIEW routines cited:

  • Standard – This option allows you to select a rotation angle using the mouse.
  • Line, Polyline or Text – This option allow you to select an object to set as a view baseline.  It is the most useful when trying to match views to objects such as property lines or road centerlines.
  • Surveyor – This option prompts for the manual entry of a bearing or azimuth for the rotation angle.
  • Restore Due North – This option returns the screen to the orientation where North is straight up.

fall right in line with remarks made by ESRI’s Brent Jones at the 2009 Carlson User Conference who said:

“GIS changes the whole domain for surveyors,” Jones added, “And surveyors need to be ready for what’s coming next — high accuracy GIS. The key is geo-referencing,” he said. “We can use our data to communicate to our world with greater precision over greater areas.”

In my opinion, a User Coordinate System (UCS, by its very definition), takes the data one step further away from being geo-referenced. There are those that would probably argue that having data in a World Coordinate System (WCS) and at assumed coordinates of something like 5000,5000,100 is no better than using a UCS to shift this same data to a proper geo-referenced coordinate system. From a holistic stand-point, I’d tend to agree. However, what sets the WCS vs. UCS argument apart is this simple statement:

All drawings must have a WCS yet not all drawings have a UCS.

When one considers the longevity of information represented in drawings created to this point in time and then reflects on how this information might also be used in the future, I feel it is important to model that information (and subsequently allow that information to be easily extracted) in a consistent and reliable fashion. A User Coordinate System is typically only understood and used by its creator which in turn, limits its use and subsequently increases the risk of liability when the User Coordinate System isn’t known or understood by a “downstream” recipient of the drawing (survey stake-out, machine control excavation, etc).

Side note observation… Is it me or are there some parallels between UCS and custom ARX objects used in other products? When I look at how long the DVIEW vs. UCS arguments have been made, I can only surmise the length of time that will be involved to bring the non-proprietary vs. proprietary data argument to a close. I suspect it’s going to be a long, tough road.

In any event, it is my opinion that standardizing on a single WCS should provide more consistent deliverables when the drawings/projects span multiple people, offices and/or disciplines. When properly adopted, using a “twisted view” of geo-referenced data in a World Coordinate System should provide more feature-rich information now and into the future when our data is mapped onto the Earth.

Originally posted on Carlson Connection by Ladd Nelson

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