Wednesday 25 April 2012

Near Real Time Audio Mixing on #BlackBerry

With the added power and APIs of the BlackBerry OS 7 smart phones I have been able to implement generation and mixing of the ELT audio signal and noise near enough to real time for me to include a workable Aural Null simulator in our BlackBerry search and rescue navigation app. I've done real time audio programming on BlackBerry before, but handling the output streaming buffers is a challenge.

Saturday 21 April 2012

Interesting Paper on GPS Track Log Filtering

I've been working on track log filtering of GPS data points as part of the development of BlackBerry smartphone software for Search and Rescue. I found a very interesting paper by Rosen S. Ivanov. Many of his ideas have occurred to me before, but he gathers a number of useful ideas together. His paper is available as a PDF here.

Thursday 5 April 2012

Aural Null Software Nearing Completion

Wow, who knew I could get so busy over the winter time. I have been making progress, but didn't have time to blog about it. I have completely refactored my navigation library. Not only is it less prone to errors due to the fact that the Earth is not really spherical, but it actually runs faster now too.

The Aural Null calculation is now very stable since I'm using the Graham Scan to ensure the points are all on a convex hull. This has the added benefit of ordering the point so the polygon is right handed, which also makes computation of the fix faster and more stable.

Here are some screen shots of a couple of test runs: