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

[Mike Collinson]

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&country=US

If I remember, http://sirius.chinalake.navy.mil/satpred/, is a good one, but it is dead when I just checked it.

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