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Bad weekend?

Rockin Roddy

By Rockin Roddy
in GPS technology and devices

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Rockin Roddy

+Rockin Roddy

Posted
Posted

When I cache, my PN-40 often puts me within a foot or even zeroes out at the cache container, it has become the norm that I often see very good coords (for whatever reasons, I think there may be more PN users in my area lol). :( This weekend called for us to attend an event which means CACHE TRIP!! Seeings the event was an hour or so off, we took the "long" way and found ourselves caching as we closed in, but I noticed something disturbing to me...my usually very stable PN seemed to be having a slight problem pointing me in the proper direction and had us jumping about. This happened enough that KAboom even suggested I should calibrate the compass (lol, gotta love the teen, he's always thinking), but this only helped minimally as I had suspected this not to be the problem.

 

So, did anyone else go out caching this weekednd...especially on Saturday? Did you see something similar to my experience? Was there something "in the air" so to speak this weekend? I won't get a chance to head out again until maybe tomorrow or this weekend, so no way to tell if this is still going on, I just wondered if anyone else had noticed this!

 

Don't get me wrong, I am MORE than happy with my PN, I don't usually see this problem either! And, while it was a bit confusing and even irritating, it really wasn't nearly as bad as I had recently seen with a certain other GPS I had bought. I am also thinking I have become spoiled due to the great accuracy I have noticed up until this last weekend!

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user13371

+user13371

Posted
Posted (edited)

Could have just been unfavorable satellite positioning from where you were at. If you don't have at least 3 or 4 (or more) in view, favorably positioned in the sky around you, the GPS won't be able to give you as good a fix. Not the fault of the GPS, that's just how the system works.

 

It's a good idea to look at the satellite/status page when you're not getting a reasonable fix. An "ideal" geometry would be having one sat straight overhead, and more scattered around the sky (not in a straight line from each other or all clumped together in one quadrant.

 

To twist a phrase, the problem may not lie in our self, but in our stars.

Edited by lee_rimar
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twolpert

+twolpert

Posted
Posted

Have had this happen once or twice. Like Lee, I first suspect a bad constellation. However, if the bearing and distance to the cache were shifting while you stood there, you could also have been the victim of multi-path problems. Or maybe your WWE championship belt buckle :( Either way, it's environmental.

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Pajaholic

Pajaholic

Posted
Posted

I use a PDA with GeoScout for caching and Navigon for road navigation. When we set off at about 1200 GMT on Saturday, Navigon was all over the place and the arrow that marked our car's position was up to 100 metres off, at times tracking alongside the road we were driving. Thankfully, it had all settled down by the time we got a few miles from the first cache.

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user13371

+user13371

Posted
Posted
...if the bearing and distance to the cache were shifting while you stood there, you could also have been the victim of multi-path problems. Or maybe your WWE championship belt buckle :( Either way, it's environmental.
I inferred from OP that it was an ongoing issue over a period of time and while moving from place to place. This diminishes likelihood of multipath problems, so we're back down to the belt buckles or constellation geometry.
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twolpert

+twolpert

Posted
Posted

What EPE were you getting? Do GPSr's take into consideration how the satellites are arranged when determining EPE? Or does it simply just count the # of strong signals & calls it a day?

 

..maybe different brands work different ways??

EPE is fundamentally based on satellite geometry, including the number of satellites which are visible and usable for navigation. To get low EPE, you need an adequate number of visible satellites, arranged in a good geometry. Signal strength isn't generally relevant to the EPE calculation. Either the unit has a strong enough signal from a given satellite to use it for navigation, or it does not.

 

Generally speaking, a good geometry has at least one satellite nearly directly overhead, with at least three more scattered around the perimeter. Bad geometry includes situations where a lot of the visible satellites are arranged in close to a straight line, or are clustered together on one side of the sky.

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user13371

+user13371

Posted
Posted (edited)

Hey, there's an echo in here, in here, in here...:(

... "ideal" geometry would be having one sat straight overhead, and more scattered around the sky (not in a straight line from each other or all clumped together in one quadrant.
...good geometry has at least one satellite nearly directly overhead, with at least three more scattered around the perimeter...
But not too close to the horizon, either. Different antenna types (patch vs quad helix) have different cutoffs re how low in the sky the sat can be for them to pick up a usable signal. Edited by lee_rimar
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user13371

+user13371

Posted
Posted (edited)

While Trimble's planning tool is cool, it may be a bit of overkill to for cachers just wanting to know how conditions are at the moment. These links can show you where the satellites pretty much in real-time (may lag a few minutes but that's not much):

 

Satellite positions and operational status, updated every 3 minutes:

http://www.nstb.tc.faa.gov/incoming/waas_sats.png

 

Google Earth layer with tons of live GPS system data:

http://www.nstb.tc.faa.gov/kml/waasclient.kmz

Edited by lee_rimar
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Suscrofa

Suscrofa

Posted
Posted

Get the Trimble planning software, update the almanach, set up your location in order to plan for the best time to cache.

Of course, it won't help if the cache has been placed a bad day !

 

http://www.trimble.com/gpsdataresources.shtml

 

Beats up horoscope and fortune teller.

 

I see the almanac file, but not the planning software. Is it free? If so, where is it at?

 

Here it is:

 

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

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okie-wan

+okie-wan

Posted
Posted

Hate to ask a question in the middle of a thread but...How do Solar Anomalies such as Solar Flares effect GPS signal Receptions? I know they can jack with other wireless signals and the news media use to report these occurences frequently.

rat beat me to it. Now that I think of it, my 60CSx did act a little goofy Sat. AM for about 2 hrs. I'm in Oklahoma. Wonder if I should have spent the extra $800 on the optional sunspot reduction filter. :)

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Gitchee-Gummee

+Gitchee-Gummee

Posted
Posted

Hate to ask a question in the middle of a thread but...How do Solar Anomalies such as Solar Flares effect GPS signal Receptions? I know they can jack with other wireless signals and the news media use to report these occurences frequently.

rat beat me to it. Now that I think of it, my 60CSx did act a little goofy Sat. AM for about 2 hrs. I'm in Oklahoma. Wonder if I should have spent the extra $800 on the optional sunspot reduction filter. :)

 

Really don't know if that would work (I did notice the "rolleyes"). Should we be the recipient of a good blast of solar flare energy, the GPSr(s) won't be much good if the satellites fall out of the sky.

 

This is primarily what the hub-bub is about concerning the year 2012, the expected Solar Max.

 

So............ rush out and get the smileys whilst you can!!! :)

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GPSlug

+GPSlug

Posted
Posted

Hate to ask a question in the middle of a thread but...How do Solar Anomalies such as Solar Flares effect GPS signal Receptions? I know they can jack with other wireless signals and the news media use to report these occurences frequently.

The ionosphere can become more active and cause both ranging errors and, in extreme cases, tracking problems. These are more frequent around solar max, but they can happen anywhere in the 11-year cycle. NOAA has a space weather site that predicts and monitors these storms. I don't see that anything significant happened this last weekend.

 

WAAS helps a lot to correct for iono errors, and gives an indication of the amount of remaining error that your receiver can use to bump up its EPE if things are bad.

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rat31465

rat31465

Posted
Posted

Hate to ask a question in the middle of a thread but...How do Solar Anomalies such as Solar Flares effect GPS signal Receptions? I know they can jack with other wireless signals and the news media use to report these occurences frequently.

The ionosphere can become more active and cause both ranging errors and, in extreme cases, tracking problems. These are more frequent around solar max, but they can happen anywhere in the 11-year cycle. NOAA has a space weather site that predicts and monitors these storms. I don't see that anything significant happened this last weekend.

 

WAAS helps a lot to correct for iono errors, and gives an indication of the amount of remaining error that your receiver can use to bump up its EPE if things are bad.

 

This is exactly where I was headed with my question. Thanks.

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