After the last post I had a few emails asking me what PRN 32 means so I thought I would list a few terms that you may come across if you start looking into the GPS system..
SV – Space Vehicle
PRN – Pseudo Random Noise
NANU – Notice Advisory to Navstar Users – there is a free mail list service run by the US Coast Guard to send GPS watchers an automatic status report.
For the latest nanus see the US Coast guard site here.
There has been some discussion recently about the new satellite PRN32 or at least an old satellite that has been recommissioned and brought into the GPS system.
It appears that some people are claiming that their GPS receivers software has been coded to count the number of satellites it can detect as 31 whereas there are now 32 satellites – I think this is a misunderstanding …I may be wrong!
It is common practice for programmers to count from 0 to 31 (ie.32) or from 1 to 32 (ie 32) when setting registers or creating arrays to handle data. I am pretty sure that however old your GPS is it can “see” 32 satellites.
There may be an unrelated error on some units eg. the Northstar 941X which started reporting SOG readings of 800 knots – not good! If you are getting strange SOG or COG readings check your supplier for a firmware upgrade – Northstar are offering a fix for their units at http://www.northstarnav.com/en/Downloads/Software-Updates/
I wrote about Mobile XT previously. My comment was not that you couldn’t get chartplotting software on a smartphone, because patently you can – the comment I made was that you couldn’t get Bluechart marine charts to be read by Garmin Mobile XT on a smartphone. After making that post Bob left a comment that he had managed to get his Garmin Mobile XT to read Bluechart charts on his phone – even though this feature was not documented!…
Just to recap,Mobile XT is Garmin’s new GPS app that will be used in the expected Mobile 10/GPS 10X and Mobile 20/GPS 20SM products.
Garmin will also be releasing Mobile XT as an update for the ageing “Que” Pocket PC software that is included with the GPS 10 Bluetooth Receiver package.
Mobile XT is a newer version of the “Que Nav” application that comes with the iQue M3 and iQue M4 Pocket PC devices.
The software is sold on microSD cards that you insert into a smartphone which has built in GPS – you can of course use a miniSD or standardSD converter to house the card if necessary, for example in a PDA.
If your smartphone also has GPRS (data service) then the software will access “Garmin Online”. This gives access to a wide range of services such as traffic, weather, hotel rates and more. It give real-time traffic information from traffic.com about traffic tie-ups and road construction that lie ahead on your route. Hotel rates, ratings and availability information comes from hotels.com. There is a good article here about the use of XT on a smartphone
So all the elements are there for using your smartphone as a handheld marine chart plotter on board your boat, and saving yourself £200 to £300 for a dedicated marine plotter.
… I haven’t tested this theory, but now I am sorely tempted, having just changed phone to the Samsung i780 that has built in GPS…but then there is Active Captain too …
I thought I would give a quick update on some of the more popular brands of AIS receiver and transponder, including some of the salient comparative features. Prices are approximate of course, when you look at your favourite online store I am sure you could better them – but it was interesting to note the price variations and also the way that features are not always a guide to price.
Note 1 : The unit has an Safety Related Message (SRM) button that allows the user to transmit a distress alert quickly and easily to all vessels and base stations within range. Often this button is programmed to engage “Silent Mode” when this “S” button is pressed. This means that it will only receive and not transmit – useful if you are worried about piracy!. The SRM feature is in addition to the international AIS specification and may not be monitored by all reception equipment. This feature does not replace use of normal VHF emergency procedures.
Note 2 : Comes with antenae
Note 3 : Comes with built in GPS – may be useful as a back up GPS to your normal one.
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June 16th, 2008|
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