Build AJAX-Based Web Maps Using ka-Map
by Tyler Mitchell | Pages: 1, 2, 3, 4, 5, 6

Adding a Key/Reference Map

You don't need to have a reference in your application, but to add one you need a REFERENCE section in the global.map file. You can add it right after the SCALEBAR...END section:

  REFERENCE
    EXTENT -180 -90 180 90
    SIZE 241 121
    IMAGE data/keymap.png
    COLOR -1 -1 -1
    OUTLINECOLOR 255 0 0
  END

This example requires a reference map image named keymap.png to be saved with the cloud image and shapefiles in the data folder. You can download Figure 2 and use it for your reference map image.

Figure 2. Reference map image (keymap.png):

ka-Map will automatically show the current extent of the map using a red box on top of the reference map, as shown in Figure 1.

Troubleshooting

Can't get ka-Map working? Here are some tips for improving your experience or finding problems with your setup.

• Use a more recent web browser version. AJAX is highly dependent on recent web browser technology.
• Check your web server aliases to make sure that the /ka-map/ directory points to the proper .../kamap-0.1.1/htdocs folder.
• Test your map file by running shp2img. If you don't have this utility already, you should get it. If it doesn't work with your map file, then ka-Map won't either. shp2img also comes as part of the precompiled FWTools collection.
• Check your temporary/cache folders. For simplicity, your map file IMAGEPATH and IMAGEURL should correspond to the $szBaseCacheDir setting in config.php. If no files are being made in that folder, then your settings are to blame. Ensure that the web server is allowed to write in that folder.
• Turn on the debug option in config.php. Setting $bDebug = true will draw the rectangles of the tiles on top of your map data. If nothing appears, then you have a problem with the ka-Map installation.
• Consider using a more recent version of ka-Map (e.g. using CVS). There are bug fixes, performance improvements, and new features in newer versions, but I have found 0.1.1 to be the most stable at present.
• More recent versions of ka-Map come with a scripts folder, which the user that the web server runs as must be able to write into that folder.
• If you are familiar with JavaScript, you could also install a debugger that can help you debug configuration problems. Consider using Mozilla's Venkman debugger.
• If you are still having problems, you can try loading the init.php file in your URL to see more runtime settings and errors (e.g. http://localhost:8080/ka-map/init.php).

Further Adventures

Testing the Map in a Web Context

The settings used in the global.map file are very simple, but in a production environment you may need to change them. You may end up wanting to change the IMAGEPATH and IMAGEURL settings to put your temporary map images somewhere else on your filesystem. These settings also specify where the web browser will be able to find the map images. If you have IMAGEURL set wrong, then the web server won't be able to make the map available to the user.

The best way to test for this is to write a simple PHP script and test running it. Take the following PHP script, save it to your kamap-0.1.1/htdocs folder and then load it up using a URL like http://localhost:8080/ka-map/maptest.php.

<?php
dl('php_mapscript.'.PHP_SHLIB_SUFFIX );
$oMap = ms_newMapObj( 'global.map' );
$oImg = $oMap->draw();
$szURL = $oImg->saveWebImage();
echo "<img src=$szURL>";
?>

If you map image is drawn, then things will work in ka-Map. If not, then you have some problems with your map file.

Pages: 1, 2, 3, 4, 5, 6

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