Mike Collinson schreef: > 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. I have an external antenna, which has a magnet. When I stick it to the frame of the bus or even the toddler's stroller/buggy, reception increases dramatically. Could this be the same effect, or did I simply increase the size of the antenna?
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