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How to get an attribute rule to calculate XY in Decimal degrees rather than the local coordinate units.

MDB_GIS

I want to have our address point automatically calculate the XY coordinates in decimal degrees whenever a new address point is created. The problem I am running into is that when I use the Geometry($feature).x/y function, it creates the point in the map coordinate system units, which is feet. Is there any way to force it to use decimal degrees?

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Accepted answers

MDB_GIS

It's a long, convoluted work around, but using other resources from this thread, I was able to create an arcade script that works for my local coordinate system (Georgia State Plane West).

// Inverse Transverse Mercator for EPSG:2240 (NAD83 / Georgia West (ftUS))
// Returns latitude, longitude in decimal degrees

// Input projected coordinates (assumes geometry is in EPSG:2240)
var E = Geometry($feature).x; // Easting (ftUS)
var N = Geometry($feature).y; // Northing (ftUS)

// Projection parameters from EPSG:2240
var a = 6378137.0;                                // semimajor axis (meters)
var inv_f = 298.257222101;                        // inverse flattening
var f = 1 / inv_f;
var e2 = 2 * f - f * f;                           // eccentricity squared

var k0 = 0.9999;                                  // scale factor
var lon0 = -84.1666666666667;                     // central meridian (deg)
var lat0 = 30.0;                                  // latitude of origin (deg)
var falseE_ft = 2296583.333;                      // false easting (ftUS)
var falseN_ft = 0.0;                              // false northing (ftUS)
var ft_to_m = 0.3048006096012192;                 // US survey foot -> meter

// helpers
function degToRad(d) { return d * PI / 180.0; }
function radToDeg(r) { return r * 180.0 / PI; }

// convert inputs into meters and remove false easting/northing
var E_m = (E - falseE_ft) * ft_to_m;
var N_m = (N - falseN_ft) * ft_to_m;

// --- compute meridian arc for latitude of origin (M0) ---
function meridianArc(phi) {
  // phi in radians
  var n2 = e2;
  var a0 = 1 - (n2/4) - (3*Pow(n2,2)/64) - (5*Pow(n2,3)/256);
  var a2 = (3.0/8.0) * (n2 + (Pow(n2,2)/4) + (15*Pow(n2,3)/128));
  var a4 = (15.0/256.0) * (Pow(n2,2) + (3*Pow(n2,3)/4));
  var a6 = (35.0/3072.0) * Pow(n2,3);
  return a * (a0 * phi - a2 * Sin(2*phi) + a4 * Sin(4*phi) - a6 * Sin(6*phi));
}

var lat0R = degToRad(lat0);
var M0 = meridianArc(lat0R);

// --- compute M (meridian arc to footpoint) from N_m ---
var M = M0 + (N_m / k0);

// --- Compute footpoint latitude (phi1) from M using series ---
var mu = M / (a * (1 - e2/4 - 3*Pow(e2,2)/64 - 5*Pow(e2,3)/256));

// e1 (called e' or e1 in many references)
var e1 = (1.0 - Sqrt(1.0 - e2)) / (1.0 + Sqrt(1.0 - e2));

// series coefficients for footpoint latitude
var J1 = (3*e1/2) - (27*Pow(e1,3)/32);
var J2 = (21*Pow(e1,2)/16) - (55*Pow(e1,4)/32);
var J3 = (151*Pow(e1,3)/96);
var J4 = (1097*Pow(e1,4)/512);

var phi1 = mu + J1 * Sin(2*mu) + J2 * Sin(4*mu) + J3 * Sin(6*mu) + J4 * Sin(8*mu);

// --- compute parameters at phi1 ---
var sin1 = Sin(phi1);
var cos1 = Cos(phi1);
var tan1 = Tan(phi1);

var N1 = a / Sqrt(1 - e2 * Pow(sin1,2));                   // radius of curvature in prime vertical
var R1 = a * (1 - e2) / Pow(1 - e2 * Pow(sin1,2), 1.5);    // meridional radius of curvature
var T1 = Pow(tan1,2);
var C1 = (e2 / (1 - e2)) * Pow(cos1,2);                    // e'² * cos²(phi1)
var D = E_m / (N1 * k0);

// --- Series expansion to get latitude (phi) ---
var term1 = (D*D / 2.0);
var term2 = (5 + 3*T1 + 10*C1 - 4*Pow(C1,2) - 9*(e2/(1-e2))) * Pow(D,4) / 24.0;
var term3 = (61 + 90*T1 + 298*C1 + 45*Pow(T1,2) - 252*(e2/(1-e2)) - 3*Pow(C1,2)) * Pow(D,6) / 720.0;

var phi = phi1 - (N1 * tan1 / R1) * (term1 - term2 + term3);

// --- Series expansion to get longitude ---
var lon_term1 = D;
var lon_term2 = (1 + 2*T1 + C1) * Pow(D,3) / 6.0;
var lon_term3 = (5 - 2*C1 + 28*T1 - 3*Pow(C1,2) + 8*(e2/(1-e2)) + 24*Pow(T1,2)) * Pow(D,5) / 120.0;

var lon = degToRad(lon0) + (lon_term1 - lon_term2 + lon_term3) / cos1;

// convert to decimal degrees
var lat_dd = radToDeg(phi);
var lon_dd = radToDeg(lon);

// change me
return lat_dd

All comments

HollyTorpey_LSA

I haven't done it for an attribute rule, but when I need a smart form to calculate latitude and longitude to populate a field, I use the script example included in this blog post: Common calculated expressions for ArcGIS Field Maps (esri.com). Scroll down to the "5. Store the geometry as an attribute" section and look at the second code block. Hope that helps!

MDB_GIS

This is what I'm going for except for the fact that it is in meters rather than feet. Although I guess I can insert a line converting the ft to meters. I will experiment with this and report back.

MDB_GIS

No matter what I do, I can't get this to work. Our data is in us feet. I cannot figure out a way to get that into meters so that it works with this script.

HollyTorpey_LSA

Is your data projected? If so, take a look at the response from @RandyBurton in this post: https://community.esri.com/t5/python-questions/feet-to-decimal-degrees-function/td-p/289896

MDB_GIS

That's a python script though, right? You can't apply that as an on the fly attribute rule, unless there is a way I am unaware of.

MDB_GIS

It's a long, convoluted work around, but using other resources from this thread, I was able to create an arcade script that works for my local coordinate system (Georgia State Plane West).

// Inverse Transverse Mercator for EPSG:2240 (NAD83 / Georgia West (ftUS))
// Returns latitude, longitude in decimal degrees

// Input projected coordinates (assumes geometry is in EPSG:2240)
var E = Geometry($feature).x; // Easting (ftUS)
var N = Geometry($feature).y; // Northing (ftUS)

// Projection parameters from EPSG:2240
var a = 6378137.0;                                // semimajor axis (meters)
var inv_f = 298.257222101;                        // inverse flattening
var f = 1 / inv_f;
var e2 = 2 * f - f * f;                           // eccentricity squared

var k0 = 0.9999;                                  // scale factor
var lon0 = -84.1666666666667;                     // central meridian (deg)
var lat0 = 30.0;                                  // latitude of origin (deg)
var falseE_ft = 2296583.333;                      // false easting (ftUS)
var falseN_ft = 0.0;                              // false northing (ftUS)
var ft_to_m = 0.3048006096012192;                 // US survey foot -> meter

// helpers
function degToRad(d) { return d * PI / 180.0; }
function radToDeg(r) { return r * 180.0 / PI; }

// convert inputs into meters and remove false easting/northing
var E_m = (E - falseE_ft) * ft_to_m;
var N_m = (N - falseN_ft) * ft_to_m;

// --- compute meridian arc for latitude of origin (M0) ---
function meridianArc(phi) {
  // phi in radians
  var n2 = e2;
  var a0 = 1 - (n2/4) - (3*Pow(n2,2)/64) - (5*Pow(n2,3)/256);
  var a2 = (3.0/8.0) * (n2 + (Pow(n2,2)/4) + (15*Pow(n2,3)/128));
  var a4 = (15.0/256.0) * (Pow(n2,2) + (3*Pow(n2,3)/4));
  var a6 = (35.0/3072.0) * Pow(n2,3);
  return a * (a0 * phi - a2 * Sin(2*phi) + a4 * Sin(4*phi) - a6 * Sin(6*phi));
}

var lat0R = degToRad(lat0);
var M0 = meridianArc(lat0R);

// --- compute M (meridian arc to footpoint) from N_m ---
var M = M0 + (N_m / k0);

// --- Compute footpoint latitude (phi1) from M using series ---
var mu = M / (a * (1 - e2/4 - 3*Pow(e2,2)/64 - 5*Pow(e2,3)/256));

// e1 (called e' or e1 in many references)
var e1 = (1.0 - Sqrt(1.0 - e2)) / (1.0 + Sqrt(1.0 - e2));

// series coefficients for footpoint latitude
var J1 = (3*e1/2) - (27*Pow(e1,3)/32);
var J2 = (21*Pow(e1,2)/16) - (55*Pow(e1,4)/32);
var J3 = (151*Pow(e1,3)/96);
var J4 = (1097*Pow(e1,4)/512);

var phi1 = mu + J1 * Sin(2*mu) + J2 * Sin(4*mu) + J3 * Sin(6*mu) + J4 * Sin(8*mu);

// --- compute parameters at phi1 ---
var sin1 = Sin(phi1);
var cos1 = Cos(phi1);
var tan1 = Tan(phi1);

var N1 = a / Sqrt(1 - e2 * Pow(sin1,2));                   // radius of curvature in prime vertical
var R1 = a * (1 - e2) / Pow(1 - e2 * Pow(sin1,2), 1.5);    // meridional radius of curvature
var T1 = Pow(tan1,2);
var C1 = (e2 / (1 - e2)) * Pow(cos1,2);                    // e'² * cos²(phi1)
var D = E_m / (N1 * k0);

// --- Series expansion to get latitude (phi) ---
var term1 = (D*D / 2.0);
var term2 = (5 + 3*T1 + 10*C1 - 4*Pow(C1,2) - 9*(e2/(1-e2))) * Pow(D,4) / 24.0;
var term3 = (61 + 90*T1 + 298*C1 + 45*Pow(T1,2) - 252*(e2/(1-e2)) - 3*Pow(C1,2)) * Pow(D,6) / 720.0;

var phi = phi1 - (N1 * tan1 / R1) * (term1 - term2 + term3);

// --- Series expansion to get longitude ---
var lon_term1 = D;
var lon_term2 = (1 + 2*T1 + C1) * Pow(D,3) / 6.0;
var lon_term3 = (5 - 2*C1 + 28*T1 - 3*Pow(C1,2) + 8*(e2/(1-e2)) + 24*Pow(T1,2)) * Pow(D,5) / 120.0;

var lon = degToRad(lon0) + (lon_term1 - lon_term2 + lon_term3) / cos1;

// convert to decimal degrees
var lat_dd = radToDeg(phi);
var lon_dd = radToDeg(lon);

// change me
return lat_dd

MHeadley

@MDB_GIS - - - You are awesome! I now have this working for Idaho State Plane West as well!!! Thank you, thank you, thank you!!

MDB_GIS

Awesome! Glad to hear it!

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