LineString.class.php in geoPHP 8

File

geoPHP/lib/geometry/LineString.class.php

<?php

/**
 * LineString. A collection of Points representing a line.
 * A line can have more than one segment.
 */
class LineString extends Collection {
  protected $geom_type = 'LineString';

  /**
   * Constructor
   *
   * @param array $points An array of at least two points with
   * which to build the LineString
   */
  public function __construct($points = array()) {
    if (count($points) == 1) {
      throw new Exception("Cannot construct a LineString with a single point");
    }

    // Call the Collection constructor to build the LineString
    parent::__construct($points);
  }

  // The boundary of a linestring is itself
  public function boundary() {
    return $this;
  }
  public function startPoint() {
    return $this
      ->pointN(1);
  }
  public function endPoint() {
    $last_n = $this
      ->numPoints();
    return $this
      ->pointN($last_n);
  }
  public function isClosed() {
    return $this
      ->startPoint()
      ->equals($this
      ->endPoint());
  }
  public function isRing() {
    return $this
      ->isClosed() && $this
      ->isSimple();
  }
  public function numPoints() {
    return $this
      ->numGeometries();
  }
  public function pointN($n) {
    return $this
      ->geometryN($n);
  }
  public function dimension() {
    if ($this
      ->isEmpty()) {
      return 0;
    }
    return 1;
  }
  public function area() {
    return 0;
  }
  public function length() {
    if ($this
      ->geos()) {
      return $this
        ->geos()
        ->length();
    }
    $length = 0;
    foreach ($this
      ->getPoints() as $delta => $point) {
      $previous_point = $this
        ->geometryN($delta);
      if ($previous_point) {
        $length += sqrt(pow($previous_point
          ->getX() - $point
          ->getX(), 2) + pow($previous_point
          ->getY() - $point
          ->getY(), 2));
      }
    }
    return $length;
  }
  public function greatCircleLength($radius = 6378137) {
    $length = 0;
    $points = $this
      ->getPoints();
    for ($i = 0; $i < $this
      ->numPoints() - 1; $i++) {
      $point = $points[$i];
      $next_point = $points[$i + 1];
      if (!is_object($next_point)) {
        continue;
      }

      // Great circle method
      $lat1 = deg2rad($point
        ->getY());
      $lat2 = deg2rad($next_point
        ->getY());
      $lon1 = deg2rad($point
        ->getX());
      $lon2 = deg2rad($next_point
        ->getX());
      $dlon = $lon2 - $lon1;
      $length += $radius * atan2(sqrt(pow(cos($lat2) * sin($dlon), 2) + pow(cos($lat1) * sin($lat2) - sin($lat1) * cos($lat2) * cos($dlon), 2)), sin($lat1) * sin($lat2) + cos($lat1) * cos($lat2) * cos($dlon));
    }

    // Returns length in meters.
    return $length;
  }
  public function haversineLength() {
    $degrees = 0;
    $points = $this
      ->getPoints();
    for ($i = 0; $i < $this
      ->numPoints() - 1; $i++) {
      $point = $points[$i];
      $next_point = $points[$i + 1];
      if (!is_object($next_point)) {
        continue;
      }
      $degree = rad2deg(acos(sin(deg2rad($point
        ->getY())) * sin(deg2rad($next_point
        ->getY())) + cos(deg2rad($point
        ->getY())) * cos(deg2rad($next_point
        ->getY())) * cos(deg2rad(abs($point
        ->getX() - $next_point
        ->getX())))));
      $degrees += $degree;
    }

    // Returns degrees
    return $degrees;
  }
  public function explode() {
    $parts = array();
    $points = $this
      ->getPoints();
    foreach ($points as $i => $point) {
      if (isset($points[$i + 1])) {
        $parts[] = new LineString(array(
          $point,
          $points[$i + 1],
        ));
      }
    }
    return $parts;
  }
  public function isSimple() {
    if ($this
      ->geos()) {
      return $this
        ->geos()
        ->isSimple();
    }
    $segments = $this
      ->explode();
    foreach ($segments as $i => $segment) {
      foreach ($segments as $j => $check_segment) {
        if ($i != $j) {
          if ($segment
            ->lineSegmentIntersect($check_segment)) {
            return FALSE;
          }
        }
      }
    }
    return TRUE;
  }

  // Utility function to check if any line sigments intersect
  // Derived from http://stackoverflow.com/questions/563198/how-do-you-detect-where-two-line-segments-intersect
  public function lineSegmentIntersect($segment) {
    $p0_x = $this
      ->startPoint()
      ->x();
    $p0_y = $this
      ->startPoint()
      ->y();
    $p1_x = $this
      ->endPoint()
      ->x();
    $p1_y = $this
      ->endPoint()
      ->y();
    $p2_x = $segment
      ->startPoint()
      ->x();
    $p2_y = $segment
      ->startPoint()
      ->y();
    $p3_x = $segment
      ->endPoint()
      ->x();
    $p3_y = $segment
      ->endPoint()
      ->y();
    $s1_x = $p1_x - $p0_x;
    $s1_y = $p1_y - $p0_y;
    $s2_x = $p3_x - $p2_x;
    $s2_y = $p3_y - $p2_y;
    $fps = -$s2_x * $s1_y + $s1_x * $s2_y;
    $fpt = -$s2_x * $s1_y + $s1_x * $s2_y;
    if ($fps == 0 || $fpt == 0) {
      return FALSE;
    }
    $s = (-$s1_y * ($p0_x - $p2_x) + $s1_x * ($p0_y - $p2_y)) / $fps;
    $t = ($s2_x * ($p0_y - $p2_y) - $s2_y * ($p0_x - $p2_x)) / $fpt;
    if ($s > 0 && $s < 1 && $t > 0 && $t < 1) {

      // Collision detected
      return TRUE;
    }
    return FALSE;
  }

}

Classes

Name	Description
LineString	LineString. A collection of Points representing a line. A line can have more than one segment.