Latest Contributions by ChuckTurlington

‎09-09-2018

Hello, I am using ArcMap 10.4.1. I would like to turn off the "On the Fly Projection" capability temporarily if possible. Is it possible to do this and if so, how can I turn it off?

‎09-04-2018

‎09-04-2018

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?

‎09-04-2018

Hello, I am using ArcMap 10.4.1. I would like to match the datum between AutoCAD and ESRI ArcMap. However, I do not see the datum in the AutoCAD selections, comparing the WKT ESRI information and the AutoCAD options. The coordinate system I am looking for in ArcMap is designated as LL84 in AutoCAD, which is the WGS84 coordinate reference system, but do not see the flattening value matching. Is there a better way I can search for the correct datum/coordinate reference system that will match AutoCAD?

‎02-14-2018

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?

‎02-14-2018

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.

‎02-13-2018

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

‎02-12-2018

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

‎02-12-2018

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).

‎02-12-2018

Hello, I am using ArcMap 10.4.1. I am performing a projection from WGS84 to NAD83, NC, USFeet. The projection dialog is shown in the attached screenshot. The data I am trying to project did not initially have coordinates but I was able to perform a "calculate geometry" to establish the latitude and longitude in the attribute table of the data. However, I am unclear why the projection does not appear valid, yet I am meeting the criteria, as far as I know. Any suggestions are welcome, thanks in advance for your help.

‎10-04-2017

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...

‎10-04-2017

Hello, I am using ArcMap 10.4.1. I am still studying the concepts of projections. I understand the ideas behind the developable surfaces and learned from several books that the surfaces are just an idealized way to explain the concepts of projections but that the developable surfaces are not literal in the calculation of a projection. It seems to me that the math behind a projection would be like a vector intersecting the developable plane, normal to the surface, and the calculated change in location from an initial lat-long position, gives the new projected location. However, if the developable surface is not literal in the projection calculation, it does not make sense without some consideration for the developable surface, it seems to me. Even to use 3 dimensional trigonometry, treating a position on elliptical datum and the new point position on the developable surface, considers the developable surface in the projection. Is it possible that the projection calculation really does utilize the developable surface, and the claim that it does not, is only in reference to Grid Based projections ?

‎10-04-2017

Hello, I am using ArcMap 10.4.1. I am still reviewing the basics of map projections and came across the concept of planar projections not fully touching at edges, due to distortion, if for example, the globe was projected using a planar stereographic type Planar Projection. However, I it seems to me that none of the State Plane zones would likely "stich" together seamlessly at the edges either. But I also thought one of the advantages of the State Plane System was that it offered continuity between large areas that are projected. So I have to ask, do the State Plane projections between states touch seamlessly at edges, or can one expect a distorted miss-alignment along zone edges ?

‎08-23-2017

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

‎08-23-2017

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.

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Date Last Visited	‎10-17-2021 11:41 PM

My Ideas

Latest Contributions by ChuckTurlington

On the Fly Projection

Re: Datum

Re: Datum

Datum

Re: ArcMap-Projection

Re: ArcMap-Projection

Re: ArcMap-Projection

Re: ArcMap-Projection

Re: ArcMap-Projection

ArcMap-Projection

Re: ArcMap - Calculation Based Projections

ArcMap - Calculation Based Projections

ArcMap-SPCS Zone Edge Distortions

Re: ArcMap - Flat Environment v.s. 3D Environment

Re: ArcMap - Flat Environment v.s. 3D Environment

Re: ACRMAP-ELLIPSOID SURFACE

IMPORTING CSV FILE