Find which side of line point falls on

RobertChaney

I've converted Dimension Annotation to points and have spatially joined the points with parcel lines based on a Match Option, Within a Distance of 30 feet.  This allowed me to get the Dimension Annotation TextString field into the parcel line attributes, which I can then use for labeling purposes.  To further this process, I'd like to know if there's a way to know which side of the parcel line the point falls on, so that I could take advantage of using the label position field that's part of the parcel fabric.

ArcGIS Pro ver. 3.1.2

Data is currently in a FGDB

Thanks,

Robert

 

AnnoPointToLine.PNG

JeffBarrette_0-1728313053878.png

RobertChaney

@MikeMillerGIS was kind enough to modify his arcade expression which was originally suggested by HungGi.

Mike's expression (listed below) was able to do what I needed and will help out going forward with working on migrating dimension annotation to labels.  All I needed to do was replace the "LineFC" with my line feature class, then insert the expression in the Calculate Field on my point feature class.  I can use this info to assign the label position so that the label remains consistent with the side of the parcel line where the annotation was located.

// The Road Centerline feature set
var line_class = FeatureSetByName($datastore, "LineFC", ["OBJECTID"], true);


// *************       Functions            *************

function find_closest_line() {
    // Find closest line segment to $feature. Limit search to specific radius.
    var candidates = Intersects(line_class, Buffer($feature, 30, "feet"));

    var shortest = [1e10, null];
    for (var line in candidates) {
        var d = Distance($feature, line)
        if (d < shortest[0]) shortest = [d, line]
    }
    return shortest[-1]
}

function return_side_of_Line(point_feature, line_feature) {
    /*
        finds the closest point on line_feature from point_feature

        Args:
            point_feature: Point Geometry
            line_feature: Line Geometry

        Returns: dictionary
            {distance: number,    // distance from point_feature to closest point
             coordinates: array,  // the coordinate pair of the closest point
             isVertex: bool,      // if the closest point is a vertex of line_feature
             lineSide: text}      // side of the line that point_feature is on based

    */

    var point_feature = Geometry(point_feature);
    var line_feature = Geometry(line_feature);
    var vertices = line_feature["paths"]
    var x = point_feature["x"];
    var y = point_feature["y"];

    // Loop through each part of the geometry and each segment, tracking the shortest distance
    var shortest = [1e10];
    for (var i in vertices) {
        var part = vertices[i];
        var previous = part[0];
        for (var j = 1; j < Count(part); j++) {
            var current = part[j];
            var result = pDistance(x, y, previous["x"], previous["y"], current["x"], current["y"]);
            if (result[0] < shortest[0]) shortest = result
            previous = current;
        }

    }

    // Couldn't find anything
    if (Count(shortest) == 1) return null

    return  shortest[3]
}

function pDistance(x, y, x1, y1, x2, y2) {
  // adopted from https://stackoverflow.com/a/6853926
  var A = x - x1;
  var B = y - y1;
  var C = x2 - x1;
  var D = y2 - y1;

  var dot = A * C + B * D;
  var len_sq = C * C + D * D;
  var param = -1;
  if (len_sq != 0) //in case of 0 length line
      param = dot / len_sq;

  var xyz, yy;
  var is_vertex = true;
  if (param < 0) {
    xyz = x1;
    yy = y1;
  }
  else if (param > 1) {
    xyz = x2;
    yy = y2;
  }
  else {
    is_vertex = false;
    xyz = x1 + param * C;
    yy = y1 + param * D;
  }

  var dx = x - xyz;
  var dy = y - yy;
  return [Sqrt(dx * dx + dy * dy), [xyz, yy], is_vertex, side_of_line(x,y,x1,y1,x2,y2)];
}

function side_of_line(x, y, x1, y1, x2, y2) {
    // get side of line segment that a point (x, y) is on based on the direction of segment [[x1, y1], [x2, y2]]
    // adopted from https://math.stackexchange.com/a/274728
    var d = (x - x1) * (y2 - y1) - (y - y1) * (x2 - x1)
    if (d < 0) {
        return 'left'
    } else if (d > 0) {
        return 'right'
    } else {
        return null
    }
}


// ************* End Functions Section ******************


// find closest line to $feature
var closest_line = find_closest_line();
if (closest_line == null) return

// find info about the closest point on the closest line to $feature
var side_line = return_side_of_Line($feature, closest_line);
if (side_line == null) return
return side_line

  

SampleData_SideOfLine.png