BethMo Posted July 20, 2002 Share Posted July 20, 2002 Hi! I'm not a Geocacher (yet), but I stumbled upon one of your caches while doing trailwork on the Primrose Trail in Coal Creek Park (near Bellevue, Washington) -- I was hiding a bucket and shovel and found a Geocache in my hiding spot. Neat hobby -- I may have to go looking for some on purpose now! Anyway, I've been working with a local trails club on a trail mapping project, using a Garmin Etrex GPS unit. I've noticed in the last few weeks that every afternoon I start losing GPS signal, getting lots of "need clear view of sky" errors, and the problem seems to be starting earlier and earlier. At this point I've given up on doing any mapping later than about 12:30 because I can't get signals. I was wondering if anyone here knows what might cause this. Is one of the satelites malfunctioning or going below the horizon or something? Is there a web site anywhere that would give information on good and bad reception times by area? Quote Link to comment
Rubbertoe Posted July 20, 2002 Share Posted July 20, 2002 I always thought that the constellation of GPS satellites were 'ever changing' - and not necessarily the in the same place, at the same time, day after day. I do notice sometimes I'll have a cluster in a line all pretty much right overhead - and my signal will be ***... but within 15 minutes or so, it seems a whole new pattern has appeared - and the signal is fine. But - if you are regularly having problems getting a good signal, even in clear skies under no trees or anything... I'll have to suspect that something else might be wrong. I use one of the more expensive eTrex models now, but even when I had the basic yellow eTrex, I never had consistant problems, day after day. Perhaps it'd be worth a swap at the store to see if it is just that one unit. Glad to see you join the community here Rob Rubbertoe - Webcam - Image Archives --== http://www.bigfoot.com/~rbatina ==-- Quote Link to comment
Rubbertoe Posted July 20, 2002 Share Posted July 20, 2002 I always thought that the constellation of GPS satellites were 'ever changing' - and not necessarily the in the same place, at the same time, day after day. I do notice sometimes I'll have a cluster in a line all pretty much right overhead - and my signal will be ***... but within 15 minutes or so, it seems a whole new pattern has appeared - and the signal is fine. But - if you are regularly having problems getting a good signal, even in clear skies under no trees or anything... I'll have to suspect that something else might be wrong. I use one of the more expensive eTrex models now, but even when I had the basic yellow eTrex, I never had consistant problems, day after day. Perhaps it'd be worth a swap at the store to see if it is just that one unit. Glad to see you join the community here Rob Rubbertoe - Webcam - Image Archives --== http://www.bigfoot.com/~rbatina ==-- Quote Link to comment
Kerry. Posted July 20, 2002 Share Posted July 20, 2002 Time of day does matter but then there's a few other variables that can/could all add up to decrease things at times. Fairly easy to see if it's purely the constellation without taking into account of obstructions etc. If you've got an approx location, time of day (either local time/offset or preferably UTC time) and date one can look at what should be in view and the conditions at the time. That ignoring obstructions but if there's mountains, trees etc then some idea of them can be included in the solution as well. If you can supply that info then I'll give you some answers. Cheers, Kerry. I never get lost everybody keeps telling me where to go Quote Link to comment
Kerry. Posted July 20, 2002 Share Posted July 20, 2002 Time of day does matter but then there's a few other variables that can/could all add up to decrease things at times. Fairly easy to see if it's purely the constellation without taking into account of obstructions etc. If you've got an approx location, time of day (either local time/offset or preferably UTC time) and date one can look at what should be in view and the conditions at the time. That ignoring obstructions but if there's mountains, trees etc then some idea of them can be included in the solution as well. If you can supply that info then I'll give you some answers. Cheers, Kerry. I never get lost everybody keeps telling me where to go Quote Link to comment
+15Tango Posted July 20, 2002 Share Posted July 20, 2002 Somewhere in these forums is a link to a site that shows where GPS signals will be degraded in certain areas due to radar activity--You might want to plug it into the search feature and see what you come up with. I would have put the link in this post myself, but I'm that good with keyword searches--I end up getting back either no results or too many results. Good luck!!! 15T www.1800goguard.com Quote Link to comment
+Desert_Warrior Posted July 20, 2002 Share Posted July 20, 2002 But being an electronics specialist, my first thought is maybe heat related. Is it possible? Since I do not know where you are, I can only guess. Mike. KD9KC El Paso, TX. Quote Link to comment
jpaikin Posted July 21, 2002 Share Posted July 21, 2002 I found this thread: http://opentopic.Groundspeak.com/0/OpenTopic?a=tpc&s=1750973553&f=5740990093&m=2060966634 which talks about reasons for bad GPS signals. It includes a number of links to external sites. By way of one of them I found this: http://www.ngs.noaa.gov/FGCS/info/sans_SA/ Perhaps some of that info will shed some light on the problem experienced by BethMo. Quote Link to comment
Forester II Posted July 21, 2002 Share Posted July 21, 2002 quote:I was wondering if anyone here knows what might cause this. Is one of the satelites malfunctioning or going below the horizon or something? Is there a web site anywhere that would give information on good and bad reception times by area? Hi all. I am a professional GPS user that lurks around here from time to time. Regarding your signal loss during the afternoon I have been working on a large project using a GIS/GPS mapping reciever and have been basically shut down after 1:00pm. If you are trying to work in a mountainous / forested area the satellite constellation has few birds high enough for the signal to penetrate the tree canopy and / or they are blocked by topography. Once you figure out what dergree of elevation the signal become viable again, then you can predict when you can receive useable signals. A pattern wiil be identifiable and this pattern has a tendency to creep a few minutes earlier every day until someone reshuffles everything. You can rent GIS/GPS mapping receivers and associated software that will do a much more accurate mapping job and you will be able to export the data into a GIS program. This software also includes mission planning capabilities so you will know when the satellites will be in your favor. Quote Link to comment
+headmj Posted July 22, 2002 Share Posted July 22, 2002 Where would you rent GIS/GPS devices? I have a project planned for later this summer locating and recording the positions of the remaining foundations of an abandoned settlement in what is now Allegany State Park in NY. Quote Link to comment
+OzzieSan Posted July 23, 2002 Share Posted July 23, 2002 Check out survey suppliers in your area. Quote Link to comment
+Absolut&KittyKat Posted July 23, 2002 Share Posted July 23, 2002 Sun Spot activity? 34°22.000/-118°30.000ish Quote Link to comment
+Jumpmaster Posted July 23, 2002 Share Posted July 23, 2002 quote:Originally posted by headmj:Where would you rent GIS/GPS devices? I have a project planned for later this summer locating and recording the positions of the remaining foundations of an abandoned settlement in what is now Allegany State Park in NY. You can try, as Team 5-oh suggested, to get your local surveyors to rent/loan the stuff to you, but I seriously doubt they would do it. GPS equipment that you're probably looking for (differential) is generally very pricy. GIS (Geographic Information Systems) is a whole different thing altogether that involves computers and software as well as the knowledge of how to properly apply the technology. You won't learn it (successfully) in an afternoon. The same can be said for differential GPS equipment, for that matter. (Believe me, I tried teaching it to my labs last year during a couple of lab periods and they didn't get it!! ) If you don't need extremely accurate positioning, you might want to forego differential. If you do need your GCP's to be that accurate, you may want to consider hiring out a firm to do this for you. JM-99 Quote Link to comment
+Jumpmaster Posted July 23, 2002 Share Posted July 23, 2002 quote:Originally posted by headmj:Where would you rent GIS/GPS devices? I have a project planned for later this summer locating and recording the positions of the remaining foundations of an abandoned settlement in what is now Allegany State Park in NY. You can try, as Team 5-oh suggested, to get your local surveyors to rent/loan the stuff to you, but I seriously doubt they would do it. GPS equipment that you're probably looking for (differential) is generally very pricy. GIS (Geographic Information Systems) is a whole different thing altogether that involves computers and software as well as the knowledge of how to properly apply the technology. You won't learn it (successfully) in an afternoon. The same can be said for differential GPS equipment, for that matter. (Believe me, I tried teaching it to my labs last year during a couple of lab periods and they didn't get it!! ) If you don't need extremely accurate positioning, you might want to forego differential. If you do need your GCP's to be that accurate, you may want to consider hiring out a firm to do this for you. JM-99 Quote Link to comment
Forester II Posted July 23, 2002 Share Posted July 23, 2002 Most Trimble GPS dealers will rent them. The Pro XR model will do a good job for you. Price was around $2000 month last year. Corvallis Microtechnology manufactures and sells professional models. They are in Corvallis, Oregon. They will rent on occasion. They also have the best software solutions. Cost about $800 month. It may be cheaper and you may get better results contracting for GPS/GIS services. If you have not had training in the operation of this type of equipment your results may not be what you need. I had to use some data collected by someone that clearly had no training. This data was absolutely useless. I cleaned it up as best I could but garbage in garbage out. Quote Link to comment
Forester II Posted July 23, 2002 Share Posted July 23, 2002 Jumpmster beat me by a few minutes. Quote Link to comment
Forester II Posted July 23, 2002 Share Posted July 23, 2002 Jumpmster beat me by a few minutes. Quote Link to comment
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