PHPBuilder - GIS Mapping with PHP Page 4



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GIS Mapping with PHP - Page 4

by: Simon Moss
|
October 23, 2003

So, the code to create the map:

<?php
// These are the coordinates the location we wish to plot.<br>
// These are being passed in the URL, but we will set them to a 
// default if nothing is passed.

if(empty($long))$long = -63.10774861954596;
if(empty(
$lat)) $lat 46.2899306519141;

// First we load the background/base map. We assume it's located in same dir 
// as the script.
// This can be any format but we are using JPG in this example
// We will also allocate the color for the marker 

$im imagecreatefromjpeg("earth_310.jpg");
$red imagecolorallocate ($im255,0,0);

// Next need to find the base image size.
// We need these variables to be able scale the long/lat coordinates.

$scale_x imagesx($im);
$scale_y imagesy($im); 

// Now we convert the long/lat coordinates into screen coordinates
$pt getlocationcoords($lat$long$scale_x$scale_y);

// Now mark the point on the map using a red 4 pixel rectangle
imagefilledrectangle($im,$pt["x"]-2,$pt["y"]-2,$pt["x"]+2,$pt["y"]+2,$red);

// Return the map image. We are using a PNG format as it gives better final 
image quality than a JPG

header 
("Content-type: image/png");
imagepng($im);
imagedestroy($im);
?>
To load the map call the PHP code from an IMG tag, passing the longitude and latitude in the long and lat variables:

<img src="map_code.php?long=long&lat=lat">

 
map of world with coordinate mapped out

 
You could easily modify this code to read long/lat coordinates from a database or a delimited text file and plot multiple points.

Summary

This is a very basic script. However the basic principle will allow you to draw very complicated maps.
The important part is the getlocationcoords function - once you have geocoded your data and have the routines to plot the points on the screen, the sky's the limit!

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