farm_map.geo.inc in farmOS 7
Farm map geometry functions.
File
modules/farm/farm_map/farm_map.geo.incView source
<?php
/**
* @file
* Farm map geometry functions.
*/
/**
* Helper function for setting BCMath scale. We use this (along with
* farm_map_reset_bcscale()) in geometry functions below to consistently call
* bcscale() with a high precision, so that small latitude/longitude geometries
* can have their length/area calculated with maximum precision.
*
* @see https://github.com/phayes/geoPHP/issues/114#issuecomment-160463523
*/
function farm_map_set_bcscale($reset = FALSE) {
// If BCMath is not installed, bail.
if (!function_exists('bcscale')) {
return;
}
// The first time this function is called, we will save the current bcscale()
// value in a static variable, so that it can be reset in the future.
$scale =& drupal_static(__FUNCTION__ . 'scale');
// We will also keep track of how deep we are in nested functions, to ensure
// that the scale is not reset before it should be.
$depth =& drupal_static(__FUNCTION__ . 'depth');
if (!isset($depth)) {
$depth = 0;
}
// Reset the scale, if desired.
if (!empty($reset)) {
// If the scale has not been set, bail.
// This prevents farm_map_reset_bcscale() being called before this function.
if (!isset($scale)) {
return;
}
// Decrement the depth, and if the depth is still greater than 0, return so
// that we do not reset yet.
$depth--;
if ($depth > 0) {
return;
}
// Otherwise, reset.
// bcscale() sets the scale globally back to whatever it was originally when
// farm_map_set_bcscale() was first run, which we saved in the static $scale
// variable. We also unset the static $scale variable so that it can be set
// again later in the request, if necessary.
bcscale($scale);
drupal_static_reset(__FUNCTION__ . 'scale');
return;
}
// Set the scale, if it has not been already.
// bcscale() sets the scale globally, and returns the previous scale, which we
// save in the static $scale variable, so that we can reset later.
if (!isset($scale)) {
$scale = bcscale(24);
}
// Remember how deep we are in nested functions.
$depth++;
}
/**
* Helper function for resetting BCMath scale.
*/
function farm_map_reset_bcscale() {
farm_map_set_bcscale(TRUE);
}
/**
* Combine multiple WKT geometries into a single GeoPHP geometry object.
*
* @param array $geoms
* An array of geometry strings in WKT format.
*
* @return object|bool
* Returns a GeoPHP object, or FALSE on failure.
*/
function farm_map_combine_geoms($geoms = array()) {
// If no geometries were found, return an empty geometry.
if (empty($geoms)) {
return FALSE;
}
// Load the GeoPHP library.
geophp_load();
// If there is more than one geometry, we will wrap it all in a
// GEOMETRYCOLLECTION() at the end.
$geometrycollection = FALSE;
if (count($geoms) > 1) {
$geometrycollection = TRUE;
}
// Build an array of WKT strings.
$wkt_strings = array();
foreach ($geoms as &$geom) {
// If the geometry is empty, skip it.
if (empty($geom)) {
continue;
}
// Convert to a GeoPHP geometry object.
$geometry = geoPHP::load($geom, 'wkt');
// If this is a geometry collection, multi-point, multi-linestring, or
// multi-polygon, then extract its components and add them individually to
// the array.
$multigeometries = array(
'GeometryCollection',
'MultiPoint',
'MultiLineSting',
'MultiPolygon',
);
if (in_array($geometry
->geometryType(), $multigeometries)) {
// Iterate through the geometry components and add each to the array.
$components = $geometry
->getComponents();
foreach ($components as $component) {
$wkt_strings[] = $component
->asText();
}
// Set $geometrycollection to TRUE in case there was only one geometry in
// the $geoms parameter of this function, so that we know to wrap the WKT
// in a GEOMETRYCOLLECTION() at the end.
$geometrycollection = TRUE;
}
else {
$wkt_strings[] = $geometry
->asText();
}
}
// Combine all the WKT strings together into one.
$wkt = implode(',', $wkt_strings);
// If the WKT is empty, bail.
if (empty($wkt)) {
return FALSE;
}
// If there is more than one geometry, wrap them all in a geometry collection.
if ($geometrycollection) {
$wkt = 'GEOMETRYCOLLECTION (' . $wkt . ')';
}
// Convert to a final GeoPHP geometry object and reduce the geometry.
$geometry = geoPHP::load($wkt, 'wkt');
$geometry = geoPHP::geometryReduce($geometry);
// Return the geometry.
return $geometry;
}
/**
* Calculate latitude degree length at a given latitude. Equations are taken
* from https://en.wikipedia.org/wiki/Geographic_coordinate_system#Expressing_latitude_and_longitude_as_linear_units
*
* @param $lat
* The latitude to calculate degree length at, in degrees.
*
* @return string
* Returns the length of a degree of latitude at the given latitude as a
* string, in meters.
*/
function farm_map_lat_deg_len($lat) {
// Load GeoPHP.
geophp_load();
// Set BCMath scale.
farm_map_set_bcscale();
// Convert degrees to radians.
$lat = deg2rad($lat);
// Define coefficients. These are copied from
// http://gis.stackexchange.com/questions/75528/length-of-a-degree-where-do-the-terms-in-this-formula-come-from
$m1 = 111132.95255;
$m2 = 559.84957;
$m3 = 1.17514;
$m4 = 0.0023;
// If BCMath is available, use that. Otherwise, use normal PHP float
// operations.
if (geoPHP::bcmathInstalled()) {
$length = bcsub($m1, bcadd(bcmul($m2, cos(bcmul(2, $lat))), bcsub(bcmul($m3, cos(bcmul(4, $lat))), bcmul($m4, cos(bcmul(6, $lat))))));
}
else {
$length = $m1 - $m2 * cos(2 * $lat) + $m3 * cos(4 * $lat) - $m4 * cos(6 * $lat);
}
// Reset BCMath scale.
farm_map_reset_bcscale();
// Return the length.
return (string) $length;
}
/**
* Calculate longitude degree length at a given latitude. Equations are taken
* from https://en.wikipedia.org/wiki/Geographic_coordinate_system#Expressing_latitude_and_longitude_as_linear_units
* See also http://gis.stackexchange.com/questions/75528/length-of-a-degree-where-do-the-terms-in-this-formula-come-from
*
* @param $lat
* The latitude to calculate degree length at, in degrees.
*
* @return string
* Returns the length of a degree of longitude at the given latitude as a
* string, in meters.
*/
function farm_map_lon_deg_len($lat) {
// Load GeoPHP.
geophp_load();
// Set BCMath scale.
farm_map_set_bcscale();
// Convert degrees to radians.
$lat = deg2rad($lat);
// Define coefficients. These are copied from
// http://gis.stackexchange.com/questions/75528/length-of-a-degree-where-do-the-terms-in-this-formula-come-from
$p1 = 111412.87733;
$p2 = 93.50412;
$p3 = 0.11774;
// If BCMath is available, use that. Otherwise, use normal PHP float
// operations.
if (geoPHP::bcmathInstalled()) {
$length = bcsub(bcmul($p1, cos($lat)), bcsub(bcmul($p2, cos(bcmul(3, $lat))), bcmul($p3, cos(bcmul(5, $lat)))));
}
else {
$length = $p1 * cos($lat) - $p2 * cos(3 * $lat) - $p3 * cos(5 * $lat);
}
// Reset BCMath scale.
farm_map_reset_bcscale();
// Return the length.
return (string) $length;
}
/**
* Calculate the distance between two latitude/longitude points in meters.
*
* @param Point $p1
* The first point.
* @param Point $p2
* The second point.
*
* @return string
* Returns the distance as a string, in meters.
*/
function farm_map_distance($p1, $p2) {
// Load GeoPHP.
geophp_load();
// Set BCMath scale.
farm_map_set_bcscale();
// Build a LineString and calculate the center point.
$line = new LineString(array(
$p1,
$p2,
));
$centroid = $line
->centroid();
// Calculate the length of latitude and longitude degrees at the centroid.
$lon_deg_len = farm_map_lon_deg_len($centroid
->getY());
$lat_deg_len = farm_map_lat_deg_len($centroid
->getY());
// If BCMath is available, use that. Otherwise, use normal PHP float
// operations.
if (geoPHP::bcmathInstalled()) {
$length = bcsqrt(bcadd(bcpow(bcmul(bcsub($p1
->getX(), $p2
->getX()), $lon_deg_len), '2'), bcpow(bcmul(bcsub($p1
->getY(), $p2
->getY()), $lat_deg_len), '2')));
}
else {
$length = sqrt(pow(($p1
->getX() - $p2
->getX()) * $lon_deg_len, 2) + pow(($p1
->getY() - $p2
->getY()) * $lat_deg_len, 2));
}
// Reset BCMath scale.
farm_map_reset_bcscale();
// Return the length as a string.
return (string) $length;
}
/**
* Calculate the length of a LineString in meters.
*
* @param LineString $line
* The line to measure.
*
* @return string
* Returns the length of the line as a string, in meters.
*/
function farm_map_line_length($line) {
// Load GeoPHP.
geophp_load();
// Set BCMath scale.
farm_map_set_bcscale();
// Start with a length of zero.
$length = 0;
// Iterate through the points.
foreach ($line
->getPoints() as $delta => $point) {
// Attempt to load the previous point.
$previous_point = $line
->geometryN($delta);
// If a previous point is available
if ($previous_point) {
// If BCMath is available, use that. Otherwise, use normal PHP float
// operations.
if (geoPHP::bcmathInstalled()) {
$length = bcadd($length, farm_map_distance($previous_point, $point));
}
else {
$length += farm_map_distance($previous_point, $point);
}
}
}
// Reset BCMath scale.
farm_map_reset_bcscale();
// Return the length as a string.
return (string) $length;
}
/**
* Calculate the area of a Polygon in square meters.
*
* @param Polygon $polygon
* The polygon to measure.
*
* @return string
* Returns the area of the polygon as a string, in square meters.
*/
function farm_map_polygon_area($polygon) {
// Load GeoPHP.
geophp_load();
// If the geometry is not a polygon, bail.
if ($polygon
->geometryType() != 'Polygon' || $polygon->components[0]
->geometryType() != 'LineString') {
return $polygon;
}
// Set BCMath scale.
farm_map_set_bcscale();
// We're going to do a pseudo-projection of the polygon into a coordinate
// system that is measured in meters, and then run a standard area calculation
// on that. We'll do this by first finding the bounding box of the polygon,
// and use the lower left point as origin. Then, we'll calculate the latitude
// and longitude lengths of the polygon's centroid point, and use those to
// calculate the new point positions.
// Get the bounding box of the polygon.
$bbox = $polygon
->getBBox();
// Create an origin point.
$origin = new Point($bbox['minx'], $bbox['miny']);
// Get the polygon's centroid point.
$centroid = $polygon
->centroid();
// Calculate the latitude/longitude degree lengths at the centroid point.
$lon_deg_len = farm_map_lon_deg_len($centroid
->getY());
$lat_deg_len = farm_map_lat_deg_len($centroid
->getY());
// Iterate through the polygon's points and map them to new points.
$line = $polygon->components[0];
$new_points = array();
foreach ($line
->getPoints() as $delta => $point) {
// Calculate the distance between the point and origin.
$distance_x = $point
->getX() - $origin
->getX();
$distance_y = $point
->getY() - $origin
->getY();
// Multiply distances by latitude/longitude degree lengths to get new point.
$new_x = $distance_x * $lon_deg_len;
$new_y = $distance_y * $lat_deg_len;
// Add the new point.
$new_points[] = new Point($new_x, $new_y);
}
// Construct a new polygon.
$new_polygon = new Polygon(array(
new LineString($new_points),
));
// Calculate the area of the new polygon.
$area = $new_polygon
->area();
// Reset BCMath scale.
farm_map_reset_bcscale();
// Return the area as a string.
return (string) $area;
}Functions
Name |
Description |
|---|---|
| farm_map_combine_geoms | Combine multiple WKT geometries into a single GeoPHP geometry object. |
| farm_map_distance | Calculate the distance between two latitude/longitude points in meters. |
| farm_map_lat_deg_len | Calculate latitude degree length at a given latitude. Equations are taken from https://en.wikipedia.org/wiki/Geographic_coordinate_system#Expressing_la... |
| farm_map_line_length | Calculate the length of a LineString in meters. |
| farm_map_lon_deg_len | Calculate longitude degree length at a given latitude. Equations are taken from https://en.wikipedia.org/wiki/Geographic_coordinate_system#Expressing_la... See also… |
| farm_map_polygon_area | Calculate the area of a Polygon in square meters. |
| farm_map_reset_bcscale | Helper function for resetting BCMath scale. |
| farm_map_set_bcscale | Helper function for setting BCMath scale. We use this (along with farm_map_reset_bcscale()) in geometry functions below to consistently call bcscale() with a high precision, so that small latitude/longitude geometries can have their length/area… |