[OSM-talk] logging with precission/amount of data set to maximum

[Andy Robinson]

But bear in mind that lots of simple handheld gps units while they can often
output NMEA then can't store it, so unless you are plugged into external
logging with a pda laptop (which is not generally practical when hiking or
cycling) you have to put up with whatever Garmin or whoever decided they
would store on the unit for download. On the Etrex range that either means a
poor timestamp stripped saved log or an active track with nothing other than
location and timestamp.

Cheers

Andy

Andy Robinson
Andy_J_Robinson at blueyonder.co.uk 

>-----Original Message-----
>From: talk-bounces at openstreetmap.org [mailto:talk-
>bounces at openstreetmap.org] On Behalf Of Joerg Ostertag (OSM Munich/Germany)
>Sent: 07 September 2006 12:20 PM
>To: talk at openstreetmap.org
>Subject: Re: [OSM-talk] logging with precission/amount of data set to
>maximum
>
>On Thursday 07 September 2006 12:08, Richard Fairhurst wrote:
>> Etienne <80n80n at gmail.com> wrote:
>> > It should be noted that recording 1,000,000 tracklogs does not
>> > *automatically* guarantee one of these things.  Some user called SteveC
>> > has apparently uploaded over 6,000,000 trackpoints but hasn't got a
>> > mega-star. It's rumoured that he bought most of his trackpoints from a
>> > courier company ;-)
>>
>> I don't really have a problem with the megastar idea - it's just a bit of
>> fun.
>>
>> But as per the other day's conversation, it does discriminate against
>> those of us who use old eTrexs with auto track compression. :(
>
>I wouldn't use this feature even if i had it. Since this makes later
>computations very flaky and difficult. So if you have enough memory
>available
>in your gps it would be great to have all track points stored. This way
>you'll be able to see much more things in the track logs than you currently
>see.
>Just giving one example:
>I store my tracks locally in plain NMEA! A little more data, but a lot more
>information i later can count on.
>
>Example Sattelites in View:
>Take the satellites in view. Lets assume x is got a lock and o is no
>reception. If you see the following pattern on your satellites in view
>while
>driving:
>
>        N
>     o  |  x
>      o |  x
> W -----+------ E
>      o | x  x
>     o  |   x
>        S
>
>and then after some driving you suddenly see the following:
>
>        N
>     o  |  o
>      o |  o
> W -----+------ E
>      o | o  o
>     o  |   o
>        S
>
>You can make some suggestions on the buildings near you. Since the
>buildings
>block the GPS-signals you have a bad reception with buildings and a good
>reception without buildings. This can be taken as a suggestion for filling
>the abutters=xx tags.
>
>Example Speed:
>If you have the speed driving along a road you can get a pretty good guess
>which highway= tag this part of the street would be appropriate to tag.
>Some of you might think; that is no problem, we have the timestamps and the
>position, so we can calculate the speed later too. But the timestamps in
>your
>gpx log have a precision of 1 second. So the speed might vary by almost
>factor 2 (between 1 sec and 1.9sec) which for example at 90Km/h could also
>be
>180Km/h which is not really precise. If you get the speed directly from the
>GPS device its evaluated by measuring the Doppler shift of your signal
>which
>is pretty precise (less than 1Km/s error).
>
>
>These are only some examples why I always would store the maximum data I
>can
>get and handle from my GPS devices.
>So I would ask everyone to log with 1 point/second and if possible also
>things
>like dop,alt,speed,sats-in-view, ...
>
>-
>
>Joerg
>
>
>
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