Arcade Script For Converting From State Plane to Decimal Degrees

[RPGIS]

Hi,

I found this code that I copied from copilot and modified for my specific needs and works somewhat but needs some major corrections.

// Constants for NAD83 Georgia West (FIPS 1002)
var A = 6378137.0; // Semi-major axis for NAD83
var F = 1 / 298.257222101; // Flattening for NAD83
var E2 = (2 * F) - (F * F); // Eccentricity squared
var centralMeridian = -84.16666666666667 * (PI / 180); // Central meridian for Georgia West (degrees to radians)
var latitudeOfOrigin = 30.0 // Latitude of origin (degrees to radians)
var scaleFactor = 0.9999; // Scale factor
var falseEasting = 2296583.333333 * 0.3048006096012192; // False easting in meters (1 US foot = 0.3048006096012192 meters)
var falseNorthing = 0.0; // False northing in meters

// Function to convert State Plane (NAD83) to Latitude and Longitude
function statePlaneToLatLong(x, y) {
    x *= 0.3048006096012192; // Convert x from US Feet to meters
    y *= 0.3048006096012192; // Convert y from US Feet to meters
    x -= falseEasting;
    y -= falseNorthing;

    var m = y / scaleFactor;
    var mu = m / (A * (1 - (E2 / 4) - (3 * E2 * E2 / 64) - (5 * E2 * E2 * E2 / 256)));

    var e1 = (1 - sqrt(1 - E2)) / (1 + sqrt(1 - E2));
    
    var phi1 = mu + (3 * e1 / 2 - 27 * pow(e1, 3) / 32) * sin(2 * mu)
        + (21 * pow(e1, 2) / 16 - 55 * pow(e1, 4) / 32) * sin(4 * mu)
        + (151 * pow(e1, 3) / 96) * sin(6 * mu)
        + (1097 * pow(e1, 4) / 512) * sin(8 * mu);

    var sinPhi1 = sin(phi1);
    var cosPhi1 = cos(phi1);
    var t1 = tan(phi1) * tan(phi1);
    var c1 = E2 * cosPhi1 * cosPhi1 / (1 - E2);
    var r1 = A * (1 - E2) / pow(1 - E2 * sinPhi1 * sinPhi1, 1.5);
    var n1 = A / sqrt(1 - E2 * sinPhi1 * sinPhi1);
    var d = x / (n1 * scaleFactor);

    // Calculate latitude and longitude in radians
    var latitude = phi1 - (n1 * tan(phi1) / r1)
        * (d * d / 2 - (5 + 3 * t1 + 10 * c1 - 4 * c1 * c1 - 9 * E2) * pow(d, 4) / 24
        + (61 + 90 * t1 + 298 * c1 + 45 * t1 * t1 - 252 * E2 - 3 * c1 * c1) * pow(d, 6) / 720);

    var longitude = centralMeridian + (d - (1 + 2 * t1 + c1) * pow(d, 3) / 6
        + (5 - 2 * c1 + 28 * t1 - 3 * c1 * c1 + 8 * E2 + 24 * t1 * t1) * pow(d, 5) / 120) / cosPhi1;

    // Convert latitude and longitude to degrees
    var latitudeDeg = latitude * (180 / PI)*10;
    var longitudeDeg = longitude * (180 / PI);

    // Format results as degrees North and degrees West
    return {
        latitude: round( abs(latitudeDeg) , 6),
        longitude: round( abs(longitudeDeg) , 6)
    };
}

// Example usage with provided coordinates
var x = Geometry($feature).x; // X coordinate in US feet
var y = Geometry($feature).y; // Y coordinate in US feet

var result = statePlaneToLatLong(x, y);
console(result); // Output: {latitude: "xy.xyzxyz° N", longitude: "xy.xyzxyz° W"}
return result.latitude

[LindsayRaabe_FPCWA]

Can I suggest adding the purpose of the code to the post heading to make it more searchable? I believe it's a Lat/Long conversion code, which I know a lot of people would be looking for. Also maybe add some tags to improve search results. 

[RPGIS]

Thanks @LindsayRaabe_FPCWA for the suggestion. I went ahead and made the changes, and I am hoping that this can be used to create a function for attribute rules. I think there might be something simpler than this, but I will need to explore further.

[DavidColey]

Hello @RPGIS  - would you be able to share how you used copilot to derive your expression?  I ask because when I try to parametrize for Florida State Plane West HARN, the only differences are the centralMeridian, latitutudeOfOrigin and the scale factor.  

var centralMeridian = -82.0 * (PI / 180); // Central meridian for NAD83 HARN Florida State Plane West (degrees to radians)
var latitudeOfOrigin = 24.33333333333333 // Latitude of origin (degrees to radians)
var scaleFactor = 0.9999411764705882; // Scale factor

Other than the scale factor for HARN carrying more precision than the NAD 83 above I cannot seem to find where HARN would cause my conversions to have a 0.1 degree shift north in latitude and 0.05 shift east in longitude.

For example, when I plug in the expressions for my respective lat and lon attributes:

Pro: 27.078110470, -82.43048022

Arcade: 27.505790, -82.383999

Its interesting too because the console returns different values from the actual calculation:

{"latitude":27.851679,"longitude":-82.409632}

Any insights you can provide are appreciated, (I just don't have the trig to keep up) -

Thanks,

David

Link to a similar post with an Arcade expression that works for State Plane North / South coordinate systems (Lambert Conformal Conic)

https://community.esri.com/t5/arcgis-pro-ideas/arcade-projectas-geometry-function/idi-p/1171382/page...

@TomNeer 

[RPGIS]

I noticed that there some issues with the console values as well that I am trying to breakdown the math but this code was copied, like you said, using copilot but it is incorrect.

When I ran some tests it worked in some instances and not in others. I also noticed that sometimes it would be off by 4 degrees in some spots but I am trying to figure out where that issue is in the code.