POINT TRANSLATION METHODS

[CADEngr2014]

Hello,

I am using Civil 3D 2014.

I have performed two different point coordinate translations of the same point data and they are slightly different.  The first method is using Autodesk MAP3D functionality inside Civil 3D; I imported the points into NAD83 HARN Us Feet coordinate in Civil 3D, then exploded all the points to reduce to just linework, then I used a query to import the exploded points into a file that was set to NAD83 US feet coordinate (no HARN).  Lastly I manually moved my Civil 3D points from the HARN coordinate location to coincide with the new NAD83 US Feet coordinate location.  I used this manual method since I had very few points and did not want to use the convoluted process of exporting to *.sdf file, then to *.shp files then to recover all field data and ultimately export to a *.csv by a query report file, etc.

For the second method; I performed a data XY import into ESRI ArcMap in NAD83 HARN coordinate, then changed the coordinate to NAD83 US Feet and exported the attribute table to a text file.  When I import the new excel.csv file, the point locations are slightly different than the location obtained from performing the querry in Civil 3D.

I want to use Arc Map as my new workflow for translating point data because it appears less error prone.  I found that the CorpsCon program did not have my coordinate that I needed and Civil 3D query process has too many steps.  However, either workflow, using ESRI or Civil 3D query, does not have a basis of comparison to know if either is correct.  I tend to prefer ArcMAP since I have been using that software to acquire coordinate correct maps and appears easy to operate and relatively quick.

Does anyone have similar experinece to know if the above two workflows appear sound, and have similar preference for point coordinate translation software?

[tcorey]

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@CADEngr2014 wrote:

Hello,

...Lastly I manually moved my Civil 3D points from the HARN coordinate location to coincide with the new NAD83 US Feet coordinate location. 

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Simply moving the Civil 3D points won't do it. Aren't there scale factor and rotation to be applied as well?

Your method of using AutoCAD Map to query the linework is good. What you can do with the points is to create a Point File Format that includes the origin coordinate system (HARN) in its definition. Easy way to do this is to copy PNEZD and then edit the copy to assign the coordinate system.

Export the points from the HARN drawing using PNEZD. When you import into a drawing that has the NAD83 system assigned, pick the new point file format that has the HARN coordinate system in the definition and when you get to the dialog that offers to Do coordinate transformation if possible, check that box. The incoming points will be translated from the HARN system to the NAD83 system.

Sorry, I can't offer any advice regarding ESRI workflows.

Best regards,

Tim

[CADEngr2014 · Accepted solution]

Tim,

Your method worked, but to make it work, I had to change the point file format northing/easting headings to Grid Northing and Grid Easting headings.  I found reference to this detail in an old C3D fundamentals book, but I am not sure why I would change the column headings.  Does this sound correct that I have to change the point file format column headings to Grid?  

[sboon · Accepted solution]

Within Civil 3d Northing and Easting always refer to local site coordinates.  If you specify a coordinate system for your drawing and turn on the transformation tab then the software will calculate and display the grid coordinate values for your points.  If you don't set it then the grid values will be the same as the local North and East.

In the file format you can specify either local or grid values.  If you import grid values then they will be transformed to local.  If you import local then it doesn't matter how your coordinate system is set.

Steve
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[CADEngr2014]

Steve,

How do I know if I have grid or local coordinates to start with?

[sboon · Accepted solution]

The only way to know for sure is to get the information from the surveyor who produced the data.  Almost all of the work that I do starts in UTM NAD83 which means that eastings range from 300,000 - 700,000 and northings from 5,400,000 - 6,500,000  Our standard practice is to scale grid coordinates up to ground, then subtract 5 or 6 million from the northings.  This makes both values have six numbers to the left of the decimal, which is useful for presenting coordinates in table etc, and makes it obvious which type of coordinates you're using.

Steve
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