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State Plane Coordinates for Arkansas

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Nate The Surveyor
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What is a good reference for Arkansas State Plane coords?

The whole survey world is deeply enmeshed in SPC, and I need to read up on it.

And, what is the Central Meridian of Arkansas North, and Arkansas South, and are they the same?

Another thing is the year by year iteration, where things shift a little. (I might not be saying that right)

Thank you, kindly



Posted : October 13, 2021 11:22 am
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PDF page 74.   The projection coordinate system probably hasn't changed since it was defined, but it is used with whichever NAD83 datum realization you are using (2011, etc.).

Posted : October 13, 2021 11:49 am
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USGS Professional Paper 1395

 Central Meridian for both North Zone (0301) and South Zone (0302)

92° West

YES, the State Plane Coordinate Values "change" on a given point (station) as each NAD83 realization modifies the underlying Latitude/Longitude of said point.


Posted : October 13, 2021 11:54 am

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If I need to know the projection parameters of a state plane zone I go to Trimble............oh wait,,,,,,never mind.

Anyway, from TBC:

Arkansas is a Lambert projection state, the north zone has an origin lat of N34d20', origin long of W92d,,,,,,Parallel 1 is lat N36d14',,,Parallel 2 is N34d56'.

Hope that helps.

oh, false N=0' false E=1,312,333.333' (USfeet)

Central meridian passes through the origin point.


Posted : October 13, 2021 12:29 pm
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Everything that you need to know about Arkansas SPC


Posted : October 13, 2021 12:52 pm
Norman Oklahoma
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The Manual 5 that has been linked is the go-to for zone definitions, but pretty tough ploughing to learn about projection systems generally.

Try out the Caltrans video on the subject - even though it is specifically referenced to Cali. Also the Caltrans Survey Manual.  Closer to home there is the Arkansas DOT Survey Manual for local flavor. Almost every state DOT has a manual. 

Elementary Surveying has 50 pages on the subject - you don't need the latest edition.    GPS for Land Surveyors is a must have, IMO.  

Tons of youtube videos in general. There is no one single go-to source. Dig in, take a little from each, and build your base.  

It is difficult to separate the subjects of projections, datums, control surveys, GPS, and adjustments.    

Posted : October 13, 2021 12:54 pm

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Manual 5 can be tough to plough through.  In today's technological world, it's probably more important to know how the equipment uses state plane than to know all of the math behind it. Loyal published the parameters page for AR North and South zones. I thought I'd add a little context by using them to create a picture of the AR South zone.

The first picture shows AR South from the Pole to the Equator with SPC coordinates for both. The constant K on Loyal's picture is the distance from the Pole to the Equator (the mapping radius) on the AK South projection. The coordinates are fairly easy to compute on the Central Meridian, just adding and subtracting. Every point on the map has a mapping radius, the map distance from it to the pole.

Note the curved parallels of latitude characteristic of a Lambert map. You can check the Equator coordinates with NCAT, but you have to enter the State Plane coordinates and solve for Lat/Lon. The Pole is a bit tougher. Geometrically, when you flatten the cone, there is a space left between the surface of the cone and the pole. That causes calculations to hit that old bugaboo, infinity. However, if you enter Easting 400,000, Northing 10,004,000, NCAT will show that you're on the right path.

The second picture zooms in to the more relevant part of the projection.

The segment from Point A goes to the Pole. I put it in to illustrate convergence on a Lambert projection. The direction on the earth's surface to the Pole is North, but on AR South, that direction is not parallel to the map's central meridian. The difference is the convergence of the meridians.

It's fun stuff to explore and today's technology makes it fairly easy for us. Those old guys back in the day were the smart ones. 

Posted : October 14, 2021 9:14 am
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Oops. Should be AR, not AK.

Posted : October 14, 2021 10:12 am