Latest Contributions by ChuckTurlington

Dan, Thanks again for your help.  I did find the correct datum but I notice that the flattening is not the same as what Autodesk reports, see attached screen shots.  However, the EPSG code matches and the imported aerial imagery appears to align with the site correctly.  For my own understanding, is there a way I can search in ArcMap for the EPSG code when trying to match between Autocad or MicroStation to ESRI AcrMap? ... View more

Dan, I find the "Project" tool in ArcToolbox, is being referred to as a transformation tool.  Is the term "projection" and "transformation" being used interchangeably here, or is there a method for just performing transformations? ... View more

Melita, My understanding is the geographic coordinate system is based on a 3d ellipsoid (correct me if I am wrong), that uses latitude and longitude.  My thought of using the GRS80 was to Transform the WGS84 ellipsoid GCS to another ellipsoid that is used as a reference for North America, GRS80.   Then perform a Projection from GRS80 to State Plane (NC) NAD83 US Feet.  I think you are saying I cannot go from WGS84 to a generic GRS80 unless it is associated with a defined coordinate reference system such as NAD83.  However, I am concerned that NAD83 is only a projected, grid type CRS and will not align well if I am starting with the WGS84 GCS.  However, I am assuming that the Projection option under the data management tools will not perform a transformation but only the projection.  If I need both transformation and then a projection, I assume I need to manually make those selections to perform each step separately.  If my understanding above is not correct, please inform. ... View more

Melita, Thanks for your response, I really appreciate your thoughts on the subject and moral support most of all. Because I closed the online chain, I was unable to respond there, so will try this email, hope it is received. I found that your suggestion does not resolve the problem, after tying it, I get the same error message. However, I think my earlier assumption may be the snag; assuming the software is making the transformation automatically with the projection. The explanation for the error appears at the right hand pane (see below screen shot), and is suggesting I should project from GCS_GRS_1980 to NAD_83_UTM_Zone_22N. However, the error still persists even with that workflow. I have had better luck with going from the GCS to GRS80 and then to state plane as a projection, but there was still a yellow shield error symbol. I think it is best to do the transformation explicitly first from WGS84GCS to GRS80, then project to NC Nad83 US Feet. Per our earlier conversations, I believe the vertical datum would be treated with a similar approach. If you have any other suggestions or think I am off base, do not hesitate to let me know I am wrong. Thanks again for your help. Regards, Chuck Turlington CAD Designer ... View more

Was that the problem with my attempt; the transformation was not available in the projection I was trying to do ? ... View more

Dan, My purpose for doing the transformation and projection from WGS84 to NAD83 is to get an export of the points so I can re-import into cad.  I am using the more superior ArcMap coordinate tools to perform the transformation/projection prior to importing into cad.  If I just change the GCS without explicitly transforming/projecting, my data will still reside as a WGS84 format, and will not give me what I need for a cad import.  Should I be transforming the data, and then due a projection as a stepwise approach or is there a better way than what I tried with the projection tool (assuming transformation is done in background). ... View more

Hi Dan, Thanks again for your feedback and expertise on this subject.  I am aware of some of the formulae describing the calculation based projections, very long trig expressions, but no particular method in mind.  But as a generalization, I am interested to know if my novice understanding makes sense without having to become a geodesy major.  I am completing a 2-3 year research project for my own benefit as a civil design engineer, but it does not seem complete without confirmation of the above ideas, that the developable surface is a large part of the calculation... ... View more

Dan, Do you know what the software model comparison may be between ArcMap and AutoCAD ? ... View more

Dan, Thanks again for your feedback.  My problem is trying to use the right software for the job.  I had no idea that the AutoCAD environment, for example, is built off a flat "grid" system and cannot interpret correctly a 3d geographic coordinate system.  The subject of software capability is very confusing, especially when the developer includes button picks that suggest functionality that is not really there.  I am hoping to confirm that ArcMap is not developed on a similar flat grid environment and really does interpret the 3d geographic coordinate systems as expected. ... View more