Monday, December 29, 2008

Ruler and reverse geocoding

While I'm up to speed, here are a few more late Christmas presents!

There's a new ruler tool, which is enabled using the compass icon, which can now be found just below the PHG circle icon. The ruler calculates great circle distance and direction between two points. Multiple rulers can be added by clicking on the compass icon again. Clicking on a ruler endpoint marker will reveal the coordinates and address of the marker position.

Furthermore, after clicking on any target on the map, an address will be shown, if possible. The address is obtained using Google's reverse geocoding service. The service may or may not be available in your area, and the data is received with a small delay after the info balloon is first opened.

Improved panning speed

I've just added javascript code to delete path points which are out of the current view. This reduces browser memory leakage and speeds things up considerably when browsing around the real-time APRS map. You'll notice this when panning away from and area, and then back - it'll take a couple of seconds to reload the map points from the server.

Sunday, December 28, 2008

PHG antenna direction plotting

Last night I figured out the math to plot nice cardioid patterns, and this morning I finally got the rotation right, so now the PHG plotting shows the directivity parameter, too. It's been requested by quite a few users since I got the circles going.

The first image shows a PHG plot with an omni pattern (no directivity), and the second image shows a PHG plot with a directional antenna pointing at 135° (southeast). Please bear in mind that these plots describe very rough approximations and best guesses about the station's service range.

You can generate a PHGR comment extension for your digipeater or igate using the PHG calculator. Please monitor your station's receiver performance and adjust the PHG settings to match the observed range.

Sunday, December 21, 2008

iPhone and iPod Touch fixes

Google has recently fixed a couple of bugs in the Google Maps API code, and both map controls and events have suddenly started working using the iPhone web browser. I've put them back in now, and the real-time APRS map is suddenly much more functional. Thanks for the little Christmas present, Google!

Look for me on HF digital modes during the Christmas holidays, I'm trying to be active from a few countryside locations.

gnuais 0.1.0 released

gnuais 0.1.0 can now be downloaded from SourceForge. It's an AIS decoding program for Linux, licensed under the GPL. Attach it to the 9600-bit/s data capable discriminator output of a VHF FM receiver, tune the rx on the marine VHF channel 87B (161.975 MHz) or 88B (162.025 MHz), and you'll be able to receive position data from nearby vessels.

Version 0.1.0 has an improved DSP decoder (thanks to Tomi Manninen, OH2BNS) and it can also upload AIS data to using the new JSON AIS protocol. If you wish to share your AIS data with, please drop me an email - the address is on the Profile page of this blog.

This is still an alpha quality release, so there are some caveats - the local GUI isn't working, and SoundChannels should be set to both (other settings will probably not work). The installation instructions are not very good either. If you've compiled software on Linux before, set up an igate, and played with soundmodem or gmfsk, installing should be pretty easy. It's an open-source project, so contributions are welcome!

Saturday, December 20, 2008

AIS data exchange with MarineTraffic

We've recently started mutually exchanging AIS data with gets AIS data from MarineTraffic, and MarineTraffic gets what we have. This improves the coverage of both services significantly, as there wasn't much overlap before.

The peering is still being tested and the protocol improved, so it might be a bit flaky for a while, but generally it seems to work.

We're not converting AIS data to APRS format, and it is not my intention to do so - too much valuable information would be lost in the conversion process, and the APRS-IS network simply is not there for this purpose.

We've specified a new JSON based protocol which is also useful for feeding AIS data from receiving stations to these services. There is already a working Perl implementation for converting an NMEA AIS stream to the JSON AIS protocol for uplinking to, it's currently being tested on a couple of receiving sites. I'm hoping the author of the client will release it in the near future.