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add geo functions

master 1.1.0
Aaron Parecki 3 years ago
parent
commit
1117e29c69
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3 changed files with 96 additions and 1 deletions
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      README.md
  2. +2
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      composer.json
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      src/geo.php

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README.md View File

@ -7,6 +7,7 @@ This project provides several helpful utilities for working with PHP projects, a
* `p3k\url` - helpful functions for parsing and building URLs
* `p3k\cache` - a simple caching helper backed by Redis
* `p3k\utils` - miscellaneous functions
* `p3k\geo` - geo functions for calculating distance and other things
* `p3k\global` - sets the timezone to UTC (you're already storing all your dates in UTC, right?)
PHP Support

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composer.json View File

@ -23,7 +23,8 @@
"src/url.php",
"src/utils.php",
"src/date.php",
"src/cache.php"
"src/cache.php",
"src/geo.php"
]
},
"autoload-dev": {

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src/geo.php View File

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<?php
namespace p3k\geo;
//RamerDouglasPeucker
//Reduces the number of points on a polyline by removing those that are closer to the line
//than the distance $epsilon.
//The polyline is provided as an array of arrays, where each internal array is one point on the polyline,
//specified by easting (x-coordinate) with key "0" and northing (y-coordinate) with key "1".
//It is assumed that the coordinates and distance $epsilon are given in the same units.
//The result is returned as an array in a similar format.
//Each point returned in the result array will retain all its original data, including its E and N
//values along with any others.
function ramerDouglasPeucker($pointList, $epsilon)
{
if(count($pointList) == 0)
return array();
// Find the point with the maximum distance
$dmax = 0;
$index = 0;
$totalPoints = count($pointList);
for ($i = 1; $i < ($totalPoints - 1); $i++)
{
$d = $this->_perpendicularDistance($pointList[$i][0], $pointList[$i][1],
$pointList[0][0], $pointList[0][1],
$pointList[$totalPoints-1][0], $pointList[$totalPoints-1][1]);
if ($d > $dmax)
{
$index = $i;
$dmax = $d;
}
}
$resultList = array();
// If max distance is greater than epsilon, recursively simplify
if ($dmax >= $epsilon)
{
// Recursive call
$recResults1 = $this->_ramerDouglasPeucker(array_slice($pointList, 0, $index + 1), $epsilon);
$recResults2 = $this->_ramerDouglasPeucker(array_slice($pointList, $index, $totalPoints - $index), $epsilon);
// Build the result list
$resultList = array_merge(array_slice($recResults1, 0, count($recResults1) - 1),
array_slice($recResults2, 0, count($recResults2)));
}
else
{
$resultList = array($pointList[0], $pointList[$totalPoints-1]);
}
// Return the result
return $resultList;
}
// http://www.loughrigg.org/rdp/
//The author has placed this work in the Public Domain, thereby relinquishing all copyrights.
//You may use, modify, republish, sell or give away this work without prior consent.
//This implementation comes with no warranty or guarantee of fitness for any purpose.
//=========================================================================
//An implementation of the Ramer-Douglas-Peucker algorithm for reducing
//the number of points on a polyline
//see http://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm
//=========================================================================
//Finds the perpendicular distance from a point to a straight line.
//The coordinates of the point are specified as $ptX and $ptY.
//The line passes through points l1 and l2, specified respectively with their
//coordinates $l1x and $l1y, and $l2x and $l2y
function perpendicularDistance($ptX, $ptY, $l1x, $l1y, $l2x, $l2y)
{
$result = 0;
if ($l2x == $l1x)
{
//vertical lines - treat this case specially to avoid divide by zero
$result = abs($ptX - $l2x);
}
else
{
$slope = (($l2y-$l1y) / ($l2x-$l1x));
$passThroughY = (0-$l1x)*$slope + $l1y;
$result = (abs(($slope * $ptX) - $ptY + $passThroughY)) / (sqrt($slope*$slope + 1));
}
return $result;
}
// Calculate the Great Circle distance between two points, in meters
function gc_distance($lat1, $lng1, $lat2, $lng2) {
return ( 6378100 * acos( cos( deg2rad($lat1) ) * cos( deg2rad($lat2) ) * cos( deg2rad($lng2) - deg2rad($lng1) ) + sin( deg2rad($lat1) ) * sin( deg2rad($lat2) ) ) );
}

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