On this site you can find my calculators for conversion between various mapping systems, Amateur Radio locator, and the UK national grid. These should work on any modern browser that supports Javascript, such as Safari, Chrome, Internet Explorer, Firefox, Opera, etc.

I have tried to make calculations as good as possible, using methods based on Ordnance Survey documents. This includes 7 parameter Helmert datum transormation so that error are minimised when dealing with the National Grid and GPS readings. All the code is embedded in the HTML files so you can download the page and run it locally. I am also expanding the sections showing how you can use this code in your own web pages or calculators.

How do they work? I am often asked for information on how to calculate locators and the like. To make it easy, here are worked examples of common calculations.

Roger Muggleton, updated February 2014 email