Latest Contributions by ChuckTurlington

‎03-01-2019

Hello, I am using ArcMap 10.4.1 I have reviewed the raster image clipping workflow: drilling down into arc toolbox and selecting raster, clip. The tiff image I have is a digital photograph, high resolution, aerial type. However, I found that the ArcMap takes too long to clip the image, or fails altogether. I filled-in the clip dialog with different selections to try and optimize the processing. I assume the size of the image is a factor in it taking a long time to clip or failing to clip. Does anyone know what selections would be best for a large tiff image (2.5E6 KB), to optimize the clipping process, or is there another workflow altogether that would be better to try?

‎02-26-2019

Melita, Thank you for your support with all my questions. The subject of a multi-step procedure to transform and/or project a datum(s), is a very technical subject, with many different exceptions and rules I am learning. I guess, if I do not get a transformation/projection path listed in the right hand panel in ArcMap, then I need to try a different "logical" step" until I get a path that can lead to a transformation/projection. Or can I assume that I will always go from the projected datum to the geographic datum, transform to the new geographic datum, then project back to the new projected datum?

‎02-25-2019

Dan, Are there multi-steps outlined in a white paper for other coordinate reference changes such as WGS84 to NAD83, and for vertical transformations/re-projections such as MSL to NAVD88, or NVGD29 to MSL or NAVD88, etc.? We get a variety of different coordinate references and datums, and often have difficulties getting a proper transformation/projection without a lot of time and headache. It seems I may not be using the correct multi-steps to get the desired results. Also, some other software like NGS tools, I believe do not perform these multi-steps automatically, so require some additional user knowledge of what the multi-steps are to get proper results.

‎02-25-2019

Dan, Are these steps performed automatically, or is the user expected to know what steps to perform in such a coordinate system change, as in the example screen shot ?

‎02-24-2019

Hello, I am using ArcMap 10.4.1. After watching the ESRI video presentation titled "Introducing Coordinate Systems and Transformations", under the subtitle "What is Happening When We Project Data?", under Case 2: Each PCS contains a different GCS; describes the projection as Un-projecting PCS A1 to GCS A->Transforming Geographic Datum to GCS B->then Projecting to PCS B1 as shown graphically in the attached screen shot. After reviewing this information I am assuming that the ArcMap program is following this workflow, when the projection path is pre-defined. If the path is not pre-defined, then manually following this method is a logical solution. I have to ask if my understanding is correct; that the workflow presented may be a manual procedure if the projection path is not defined, following the above steps?

‎01-14-2019

Dan, Thanks for your interest. I have a project in Alabama, USA that is located on the south end, not very close to the coast, but close to a river connected to the coast. I have never used MSL, but I am working with an engineer that has a need to use MSL. As a designer, I would like to know what the cut-off distance is between use of a tidal gauge and/or NAVD88. I know some coastal areas use MSL, but there must be a rule for knowing when it is no longer accurate or applicable. In my limited research, I have heard of 1-2 miles as rule of thumb, but not found any reference to this in a white paper form or scientific type documentation, but there must be something?

‎01-14-2019

Dan, Thanks for your interest. I have a project in Alabama that is located on the south end, not very close to the coast, but close to a river connected to the coast. I have never used MSL, but I am working with an engineer that has a need to use MSL. As a designer, I would like to know what the cut-off distance is between use of a tidal gauge and/or NAVD88. I know some coastal areas use MSL, but there must be a rule for knowing when it is no longer accurate or applicable. In my limited research, I have heard of 1-2 miles as rule of thumb, but not found any reference to this in a white paper form or scientific type documentation, but there must be something? Regards, Chuck Turlington CAD Designer

‎01-14-2019

All, I am using ArcMap 10.4.1. I see many engineers using MSL, but I believe, should be using NAVD88 as a vertical datum. I imagine there must be a rule of how many miles upland (distance from gauge) the sea level gauge is good for. Does anyone know how far upland one can make use of Mean Sea Level accurately, before having to switch to NAVD88 or similar?

‎09-30-2018

Dan, If I understand correctly, your example applies to datums that remain the same but have different adjustments, and any differing datums with variations in physical properties like radius, etc.?

‎09-30-2018

Hello, I am using ArcMap 10.4.1. I am looking for confirmation of my understanding of the below scenario. I am trying to understand what happens when two different coordinate systems do not align. The concept appears simple but want to confirm that I am not missing something. I have attached an image of the Lambert Conic Conformal projection model showing the Grid Origin and the Geodetic Origin, as an example. It is my understanding that the grid origin (red X) would correspond to the cad/Esri program 0,0,0 (origin of northing-easting values). While the geodetic origin corresponds to the projected ellipsoid origin, centered on the map (red square). It appears that coordinate systems with different ellipsoids and units would shift the map false northing/easting to a different location, causing data to misalign. By toggling the coordinate system alone is not enough to change the map data, but by performing a transformation-projection on the data allows the software to read the northing-easting coordinate values relative to the false northing/easting of the ellipsoid that is active in coordinate definition. Does the above concept sound correct or could there be more to this concept that I am not aware?

‎09-14-2018

Yes, thank you Melita. Is the flat imagery, treated with any particular projection? The Web Mercator (EPSG 3857) is not projected, but retains the datums elliptical shape?

‎09-14-2018

Melita, Thanks again for your support, but I have to ask: the basemap imagery associated with the GCS_WGS_1984 geographic datum, inside ESRI ArcMap, is actually flat or do I assume the basemap has earth curvature in the imagery?

‎09-13-2018

Dan, In reference to your above discussion "It is 3d in the sense that there can be height values assigned. WGS84 is datum used by a geographic coordinate system ( longitude and latitude ). There will be no 3D component unless elevations are assigned to the geometry as well as the coordinates." When does the concept of Projection come into play, if datums are actually flat projected type, when one is performing a "Transformation / Projection?

‎09-10-2018

Dan, Does that mean that I cannot add elevation to anything in a projected state plane coordinate?

‎09-09-2018

Hello, I am using ArcMap 10.4.1. I have a base map that has the "GCS_WGS_1984" geographic coordinate reference system, it is my understanding that this reference system is referring to a 3d coordinate system. However, if I export the map, I assume the map is actually projected to a flat image, especially since it appears on a flat computer screen? If it is projected, what projection is used because it is not referred to as a projected coordinate but as a geographic type, which is somewhat confusing how the exported map is meant to be interpreted.

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

My Ideas

Latest Contributions by ChuckTurlington

Raster Image Clip

Re: Projection Workflow

Re: Projection Workflow

Re: Projection Workflow

Projection Workflow

Re: Mean Sea Level

Re: Mean Sea Level

Mean Sea Level

Re: ArcMap-Projection Origin

ArcMap-Projection Origin

Re: Geographic Maps

Re: Geographic Maps

Re: Geographic Maps

Re: Geographic Maps

Geographic Maps

Re: ACRMAP-ELLIPSOID SURFACE

IMPORTING CSV FILE