Which State Plane?

[Pointdump]

AutoCAD Civil 3D gives you a few choices when you choose a Coordinate System:

So what's the difference between:

• Arizona West Zone, Int. FT (or use HARN/AZ.AZ-WIF)
• HARN/AZ Arizona State Planes, West Zone, International Foot
• NAD83 Arizona State Planes, West Zone, International Foot

Dave

[Anonymous]

HARN is generally used when dealing with GPS (High Accuracy Refernce Network).

The "west zone" is refering to UTM which is LAT/LONG

9 times out of 10 you are going to use state plane -  a system for specifying positions of geodetic stations using plane rectangular coordinates

Hope this helps!

[rl_jackson]

I use this for everything

NAD83 Arizona State Planes, West Zone, International Foot

[Pointdump]

P,

Arizona has three State Plane Zones: West, Central, and East. They are Transverse Mercator Projections which follow County lines and are designed to keep distortion of distance under 1/10,000. UTM is not a State Plane Coordinate System. It splits the globe into 6-degree sections and has a maximum distance distortion of 1/2500.

HARN Points are tightly-measured (and published) Control Points across the US. What I don't understand is what they have to do with defining State Plane Coordinates.

Dave

[Pointdump]

RL,

"NAD83 Arizona State Planes, West Zone, International Foot"

That one is my first choice. I did find a "definition" Here:

PROJCS["NAD83(HARN) / Arizona West",
    GEOGCS["NAD83(HARN)",
        DATUM["NAD83_High_Accuracy_Reference_Network",
            SPHEROID["GRS 1980",6378137,298.257222101,
                AUTHORITY["EPSG","7019"]],
            TOWGS84[0,0,0,0,0,0,0],
            AUTHORITY["EPSG","6152"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,
            AUTHORITY["EPSG","9122"]],
        AUTHORITY["EPSG","4152"]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",31],
    PARAMETER["central_meridian",-113.75],
    PARAMETER["scale_factor",0.999933333],
    PARAMETER["false_easting",213360],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AXIS["X",EAST],
    AXIS["Y",NORTH],
    AUTHORITY["EPSG","2763"]]

But I don't have a NAD83 definition to compare it with.

Dave

[Pointdump]

I also posted my question on the Surveyors Forum. I got some good responses:

http://surveyorconnect.com/index.php?mode=thread&id=278894

Dave

[Anonymous]

Nice!  I started getting a little foggy towards the bottom of the surveyconnect site.  They were talking way over my head! ha  

I called a local surveyor I know and he said that ( he could be wrong) a HARN can be any type of survey.  A surveyor could go out in the woods, start a survey with arbitrary coordinates and call it a HARN.  Its not based on a projection and doesnt have to be published, but could be.  Ask the other guys and see how they respond.

Thanks Dave

Phillip

[sboon · Accepted solution]

The coordinate systems displayed in Civil3d come from the ACad Map system that Civil3d is built on top of.  The MAPCSLIBRARY command will open up a dialog with all sorts of information about ellipsoids, datums, coordinate systems and how the transformations between them operate.

Comparing the three systems listed above, they all have the same GRS1980 ellipsoid but different Datums.

Steve
Please use the Accept as Solution or Kudo buttons when appropriate

[Pointdump]

Steve,

That is EXACTLY what I wanted to know. Thank you.

Dave