How bad is the BMW nav system --- or do I have a flawed copy of the software

I have a circa 1993 Icom GP-22 GPS device.

The instruction manual says that it takes 10 minutes to collect the almanac, and that once the almanac is stored, then subsequent position calculations take from 1 to 3 minutes.

1993 - 10 minutes to collect the almanac, and 1 to 3 minutes to calculate the position.

In my experience in using the device, the 10 minutes to collect the almanac is about right, give or take a minute or two. The 1 to 3 minutes to calculate the position was also correct, with the caveat that usually the time was closer to 3 minutes than 1 minute.

Reply to
fred
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That article also has the sentence, "...Many receivers can use as many as twelve channels simultaneously, allowing quicker fixes....".

So the question becomes, can the almanac be downloaded in pieces from multiple satellites simultaneously, thus allowing the entire almanac to be downloaded in less time than it takes to download it from start to end from one satellite?

There is nothing that says a data file (i.e., the almanac) cannot be broken up and downloaded in pieces from various locations simultaneously. Indeed, that is how bit torrent works.

Reply to
fred

Well indeed. I had assumed the aGPS was using the [known] position of the mast to get approximate position of the reciver, however the article tells you it just downloads the almanac if it can (

Indeed it can, but remember these birds are doing five miles per second, so even a tiny error will put you hundreds of metres out.

As described in the article anything that helps (accurate time, approx position or knowing you are stationary) helps speed up a fix.

Anyway early 747's had a hole in the cockpit roof through which a specially designed sextant was used to get a celestial fix. On KAL 007 they got the fix OK, but then navigated on a magnetic bearing instead of a true one...

Reply to
R. Mark Clayton

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