[OSM-talk] GpsWeather: When conditions for mapping are good

[Andy Robinson (blackadder)]

Mike Collinson wrote:
>Sent: 02 January 2008 9:54 PM
>To: talk at openstreetmap.org
>Subject: Re: [OSM-talk] GpsWeather: When conditions for mapping are good
>
>At 10:11 PM 2/01/2008, ivom wrote:
>>Folks!
>>
>>>From time to time, I am suffering from the limited reception capabilities
>>of my Garmin Etrex Venture Cx. I guess this is a recognizable state of
>>being, during a mapping session in urban canyons, walking around with an
>>accuracy of 17 meters or more...
>>
>>I am looking for some sort of indication telling me, at which time-of-day
>>there would be excellent conditions for creating tracks in a dense city
>>area. Has anybody come about such a service on the web yet?
>>
>>Currently I am not planning to upgrade on the hardware side, but do not
>>hesitate to suggest different makes, models or add-ons, which would suffer
>>less from this urban canyon problem.
>>
>>Kind regards,
>>IvoM
>
>IvoM,
>
>I think what you may be after is being able to predict date/times when a)
>there is a good number of satellites in the sky around you so that your GPS
>device can get as many readings as possible and choose the best, b) the
>satellites are well distributed over the sky to help the mathematical
>calculation of the GPS device and so that they are not all blocked by a
>tall building at the same time.
>
>If so, try typing into Google: GPS Satellite predictor
>
>I came up with
>
>https://stellarsupport.deere.com/stellar/SatellitePredictor?language=en&cou
>ntry=US
>
>If I remember, http://sirius.chinalake.navy.mil/satpred/, is a good one,
>but it is dead when I just checked it.

Yeah, I used to use the Sirius link but that's dead now I think.

It's worth bearing in mind that all the manufacturers of commercial survey
grade gps products maintain sat availability services. Most of these operate
via a paid service or purchased software, however Trimble produce a useful
free tool called "Planning" that I use when I really need to know how good
its going to be out there.

http://www.trimble.com/planningsoftware_ts.asp

Cheers

Andy

>
>Unfortunately,  even that probably won't  help that much with urban
>canyoning - you'll probably have to do several runs and then tie it in with
>Yahoo imagery if you are lucky enough to have it for your area.  One tip,
>I've got my best results having my GPS device mounted in a bicycle saddle-
>bag - it provides a much more stable platform than walking.  And if you are
>walking and your device loses satellite connection, put it on a metal
>surface - a man-hole cover,  traffic-signal controllers, even large waste-
>paper bins. It seems to act as a ground-plane which improves the antenna
>gain.
>
>Mike
>Stockholm
>
>
>
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