Re: GPS unit recommendations?

Bitstring <pan.2007.11.03.21.44.56.146751@xxxxxxxxxxxxxxxxxxxx>, from the wonderful person andrew heggie <news@xxxxxxxxxxxxxxxxxxxx> said
On Sat, 03 Nov 2007 21:16:55 +0000, GSV Three Minds in a Can wrote:

If you want to save a lot of points, use the microSD card .. 2GB will go
a LONG way, even in the ridiculously inefficient .gpx format it uses.

This is a bit at odds to what Nigel implied.

Not really. Nigel said 150kB for 8 hours. That'd be about 35km tops, for me. Which'd be (on Normal, Auto setting) maybe 1000-1500 trackpoints. Nigel could tell us exactly. So it's taking 120 Bytes to store a trackpoint, which is really just X/Y (3 bytes each - Garmin uses 24 bit Lat/Lon) Z (2 Bytes .. over 64k feet you are on your own), and time (even the cr&ppiest storage of which surely can't exceed 8 bytes, working to the nearest second). So that's maybe 13 bytes of useful data (in binary).

Trust me on this .. this is what a .gpx file looks like:

<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<gpx xmlns="http://www.topografix.com/GPX/1/1"; creator="" version="1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd";>
<trk>
<name>ACTIVE LOG142737</name>
<trkseg>
<trkpt lat="52.436631" lon="-2.587410">
<ele>232.971</ele>
<time>2007-11-01T14:27:35Z</time>
</trkpt>
<trkpt lat="52.436636" lon="-2.587421">
<ele>238.621</ele>
<time>2007-11-01T14:27:41Z</time>
</trkpt>
<trkpt lat="52.436636" lon="-2.587425">
<ele>242.221</ele>
<time>2007-11-01T14:27:42Z</time>

etc etc.

Notice it's all in plain text format, each data element is tagged, and all-in-all it is approximately the least space efficient storage mechanism yet designed**. On the other hand you can store anything at all, with a few extra tags. 2 Byte elevation, in feet, has grown extra meaningless digits, and tags.

Ok, the latitude is easier to interpret than x'534 (where Garmin are using 24 bits to be 360 degree, iirc).

**Well it would be, it's merely M$'s XML with different clothes on. It even says so in the header. Now you know why M$ Office now runs like molasses.

Saving complete tracklogs to a 2GB card in gpx format each day looks like
a good option if it's possible.

No, you just turn on 'log to the microSD card' and it does it for you. You don't do any saving. You just manually clear the main tracklog (or set it to wrap round) and use the .gpx files (which are stored in parallel) later.

--
GSV Three Minds in a Can
10,002 Km walked. 1,952 Km PROWs surveyed. 35.5% complete.
.

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