Shows you where a place is on an Ordnance Survey Map

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We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

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I am also active in many other area and still look after a lot of web sites - you can find an index ((here))

Additional PHP Material example from a Well House Consultants training course
More on Additional PHP Material [link]

This example is described in the following article(s):
• Ordnance Survey - using a 'Get a map' - [link]

If you're searching for a page where you can try this code, select here

Source code: grids.php Module: H999


<?php

if ($_GET[test]) {
        $testmode = 1;
} else {
        $testmode = 0;
        header("content-type: image/jpeg");
}

/* "Let me show you where that is" */

/* This script reads a map image (from the Ordnance Survey
"Get a map service" and highlights a location you give it with
a blue square */

###############################################################
$gridrefs = <<< GRIDREFS

# Grid references - bottom left corner of square

# This file contains the two letter codes used by the British
# map reference systems.    For example, ST914628 is:
# From the West 300 x 10 + 914 = 3914
# From the South 100 x 10 + 628 = 1628
# Distances measured in tenths of a kilometre.

0 0 SV SW SX SY SZ TV
100 100 SR SS ST SU TQ TR
100 200 SM SN SO SP TL TM
200 300 SH SJ SK TF TG
200 400 SC SD SE TA
100 500 NW NX NY NZ OV
100 600 NR NS NT NU
0 700 NL NM NN NO
0 800 NF NG NH NJ NK
0 900 NA NB NC ND
100 1000 HW HX HY HZ
300 1100 HT HU
400 1200 HP
GRIDREFS;
###############################################################

foreach (explode("\n",$gridrefs) as $line) {
        $line = preg_replace("/#.*/","",trim($line));
        $fields = explode(" ",$line);
        if (count($fields) < 3) continue;
        for ($k=2; $k<count($fields); $k++) {
                $twolettersx[$fields[$k]] = $fields[0] + 100 * ($k-2);
                $twolettersy[$fields[$k]] = $fields[1] ;
                }
        }

# define the map we have and load it from file

$grid = "ST";
$east = "804";
$north = "631";
$width = "80";
$im = imagecreatefromjpeg("$width-$grid$east$north.jpg");

# Work out the area the map covers

$wide = imagesx($im);
$high = imagesy($im);
$lhs = $twolettersx[$grid] * 10 + $east - $width / 2.0 * 10.0;
$rhs = $twolettersx[$grid] * 10 + $east + $width / 2.0 * 10.0;
$bhs = $twolettersy[$grid] * 10 + $north - $width / 2.0
                / $wide * $high * 10.0;
$ths = $twolettersy[$grid] * 10 + $north + $width / 2.0
                / $wide * $high * 10.0;

# define a point we want to highlight on the map and convert it to km from (0,0)

$highpoint = "ST914628";
if ($_GET[gridref]) $highpoint = $_GET[gridref];

preg_match("/(..)(...)(...)/",$highpoint,$parts);
$xlocn = $twolettersx[$parts[1]] * 10 + $parts[2];
$ylocn = $twolettersy[$parts[1]] * 10 + $parts[3];

# Where is that on the image?

$xpixel = ($xlocn - $lhs) * $wide / ($rhs - $lhs);
$ypixel = $high - ($ylocn - $bhs) * $high / ($ths - $bhs);

# Add a symbol to show our location

$symsize = 10;
if ($_GET[ssize]) $symsize = $_GET[ssize];

$fg = ImageColorAllocate($im,0,0,128);
ImageFilledRectangle($im,$xpixel-$symsize,$ypixel-$symsize,
                $xpixel+$symsize,$ypixel+$symsize,$fg);

if ($testmode) {
        print ("$parts[1] $parts[2] $parts[3] $xlocn $xpixel<br>");
        print ("$parts[1] $parts[2] $parts[3] $ylocn $ypixel<br>");
} else {
        imagejpeg($im);
        }

?>

Learn about this subject

This module and example are covered on the following public courses:
* Learning to program in PHP
* PHP Programming
* PHP Programming
* Learning to program in PHP
Also available on on site courses for larger groups

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Past attendees on our training courses are welcome to use individual examples in the course of their programming, but must check the examples they use to ensure that they are suitable for their job. Remember that some of our examples show you how not to do things - check in your notes. Well House Consultants take no responsibility for the suitability of these example programs to customer's needs.

This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details.

Any of our images within this code may NOT be reused on a public URL without our prior permission. For Bona Fide personal use, we will often grant you permission provided that you provide a link back. Commercial use on a website will incur a license fee for each image used - details on request.

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