OpenLayers and Versioning in Aptana Studio

Jun 302011

imageThis post details how to add a Subversion (SVN) plugin to Aptana to allow you to compare OpenLayers code with previous versions.

A straw poll was taken on the OpenLayers mailing list in April 2010, and OpenLayers v3 development is taking place in git, with the central repository stored on GitHub. This means working with SVN and OpenLayers may become redundant. However as many OSGEO projects are stored in SVN with no current plans to move the same plugin and knowledge of working with SVN will still be useful.

For further details on working with SVN there is a free e-book “Version Control with Subversion” available at http://svnbook.red-bean.com/

Installing the Plugin

1. Open the Plugin Manager, by clicking on the green jigsaw piece in the toolbar below.

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OpenSource Upgrades

Jun 242010

image Moving to new versions in OpenSource has in the past been like playing Russian roulette. Just now clicking on “Upgrade to WordPress 3.0″ I thought would lead to a greater understanding of the database schema, template inconsistencies, and plug-in idiosynchrocies of WordPress as I met an inevitable “Upgrade Failed. Please see log for details” message.

But no! Five seconds later, all was successful, and everything looked as before. There have been numerous bug fixes and improvements, but after a brief look through the list I didn’t see any “killer” new features.

In the world of GIS however there are a number of important new versions coming up this summer.

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Watch out for OpenLayer Distances

Apr 292010

imageI had the fortune on my most recent project, a MapFish mapping system, of having someone else do some thorough testing. One thing that had escaped me, was both the measure tool and area tool were returning incorrect results.

The distance as-the-crow flies between Dublin and Cork is 219 kilometres (136.08 miles in old money) wheras my tool was returning 357km. Having never driven this route it didn’t set off any alarm bells. Its also not the sort of function I’d unit test, – one as its in JavaScript, and two as the sample code seemed to work “out-of the box.”

It turns out measurements are planar by default, as briefly referred to in the OpenLayers API docs (although not on the actual measure tools pages..), and there is a geodesic parameter. By default this is set to false, so in a Mercator projected map (so anything using Google, Bing, or OpenStreetMap background mapping) measurement tools will be wrong. Maybe something to check if you’ve created a system – I’ve been 6 months working with OpenLayers and somehow managed to miss this one. Continue reading »

Logging OpenLayers with Firebug

Apr 132010

imageI take it as given that anyone developing with Firefox and OpenLayers has Firebug installed. Firebug has a number of powerful tools that can make the previous nightmare of JavaScript debugging tolerable.

One feature I recently “discovered” are the logging options. It’s definitely a timesaver over my previous method of putting temporary alert(vals); throughout my code. As well as debugging the logging is very useful for automatically documenting formulae in JavaScript with worked examples that can then be pasted straight into the documentation.

An example of the logging capabilities can be seen on my sample OpenLayers page. If you already have Firebug installed you should be able to see the output similar to that below when the page loads.

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