itchytweed
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Posts posted by itchytweed
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What did you then use the decimals for?
The GPSr only display five decimals. I am getting out 8 decimals with the software. The GPSr is capable of more decimals but they are not needed for what I am trying to do. Plus, I know that the hardware can't supply a stable enough accuracy to use all the decimals.
This is all in the name of fun.
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People climb Mt. Everest because it was there. Myself, getting out the extra decimals from my GPS V was to relieve a bit of creational boredom and to really see what my unit was capable of.
First off, I used Antoinio's software available at http://artico.lma.fi.upm.es/numerico/miembros/antonio/async/
I went and made some modifications to the two packages, async and gar2rnx, to run on my copy of Linux and its hardware. The software is running on an IBM T41 laptop.
I went and did a 45 minute occupation of a site that is listed with the NGS and is part of the Wisconsin High Accuracy Reference Network that is near my office.. I can guarantee that this is a totally non-scientific test and can't be used for geodetic work. I had mounted the GPS V stick antenna on a PVC pipe 5 feet above the benchmark. The GPS V head was located in my vehicle running off of a 12 volt battery and 30 feet of 9913 coax between the antenna and the GPSr. My laptop used async to grab all the data from the GPSr over the serial link. I ended up occupying the site for 45 minutes. Also, I had the GPSr running for 3 days straight to get the unit's temperature stabilized and the crystal settled down.
I crunched the data through gar2rnx and ended up gettting a rinex file after using option -etrex. I would have loved to stay there longer than I did but there were other pending issues that had to be taken care of.
At home, I scoured the web to find out if there was a public site that post-processed L1-only RINEX files. That came up a dry hole. But, I did find this site: http://mywebpages.comcast.net/dmilbert/softs/. Dennis wrote a L1-only post processor in FORTRAN. I used the ddpr1 program. I had to work on that to get the program to compile and run under f77. I grabbed the necessary files to feed it (ephemeris and rinex for a local CORS site). When it was done crunching, I converted the X,Y and Z values into Lat Lon Height. Height was way off but Lat and Lon was within 0.5 meter.
I can't complain a bit about the result using plain antenna that picks up everything, the cars multipath from the nearby road, consumer-grade equipment,etc. The setup was a hack but it was a proof of concept that worked. Now only if I had access to a choke ring antenna and four hours of free time...
Dear Santa, I have been a good boy this year. Can I get a complete dual-receiver Thales ProMark3 with all the goodies in my stocking this year?
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If your unit keeps going to "burn-in" (what a poor choice for a function) on its own, call the manufacturer and request a replacement under warranty, if it still is. There may be a problem with the internal flash memory corrupting forcing a reinitialization.
There is no need for this to be happening and to accept this as a regular "feature" is very lame.
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when do you ,people just cut off with this kind of crap..? childish
What generated this thread, is the fact, that most of the consumer GPS models got problems, and NON of them are perfect, with trade-offs with any of them you buy. The one fact I can say is that I been able to milk out more out of GPS units with a stick antenna at 6 feet off the ground, than the GPS units with a patch, that I'm holding only waist heigh, and the fact that Garmin got tiny screens, but the big screen magellan is also lacking in data readouts, so this is the place to vent your sillyness.
I understood all that and it was funny for me also,first days and posts...but the thread got too long...it's not funny anymore..more and more people just post here all kind of rubbish,not to mention that there are new members that are misleaded into thinking that there really will be out some model with all these "features"
Being in the engineering business (professional and personal). these kind of threads are actually great. Some comments may be pure hoohah and others quite fruitful. Just remember how Pringles started.
This is where ideas start. I doubt that we will find a GPS out there with everything that we want...big screen for old eyes, L1/L2/L5 reception and processing, long battery life with easy to change out batteries, antennas that pull in signals through the nastiest canopy in the Amazon, repeatable 8 decimal accuracy, -40 F to +140 F temperature range, serial ports faster than 9600 baud (USB 2), OCXO, car and hand operation, and a few others.
I still think the best gift for the true geek cacher out there would be a choke ring antenna hat, in the mindset of Devo....
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I will just keep my GPS V.
A unit that has a patch antenna belongs in a patch....a gravestone patch!
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We have a Magellan SporTrak Pro that we got as a gift a couple of years ago. We love geocaching, but are getting frustrated by searching all over the place because we are not getting very accurate readings. Just today we tried three caches, found two and gave up on the third. The two we found showed that we were still +/- 100' away! Is this normal? It's fall and most of the leaves have dropped, and for one of the caches that showed 100' away we were in an open field! What should we expect, accuracy-wise? How can we increase our accuracy, and if we decide to buy a new GPS, which one should we choose?
Thanks for your help!
Frustrated, but still having fun!
Bear with me on this...this may get long.
The key to accuracy is timing. In a perfect world, everything would line up just right and you would be able to measure right down to a gnat's whisker. We don't live in a perfect world...darn.
If the Magellan has been in a box gathering dust bunnies on the back of the bedroom closet for a long time, it may take some time to get everything back into shape. Electronic equipment is like our bodies, it gets out of tune just sitting around. It takes time for everything to stabilize.
Now assuming that you have been using this unit for some time and it is still not behaving, there could be several reasons: multipath, buggy software, poor satellite constellations, no WAAS reception, weak batteries. I could go into a couple of other items but that is something that manufacturers do not like to hear.
Ideally, multipath is drastically minimized by using circular polarized signals. You can receive a left-handed signal on a right-handed antenna. Same idea as putting in a left-hand threaded screw into a right-hand threaded hole. The handedness of a signal changes upon bouncing off of a surface. This is a great thing about circular polarized signals.
If your software is old, I would see if Magellan has an updated firmware package for your unit. This may help out improving the accuracy. Some GPS units have almanacs hard-coded (IMHO a BIG mistake). New software updates the almanacs.
Poor constellations can give you grief. If all you are receiving are satellites that are close together, your position resolution falls off as opposed to receiving satellites that are far apart.
There has been a lot of talk about WAAS reception with the new birds being put up. The WAAS system helps compensates for our dynamic atmosphere constantly moving around and messing up the signal timings. There are precisely monumented receiving stations around that listen to the GPS signals. The system compares what it receives vs. where it is and distributes corrections via the WAAS satellites. These corrections allow my GPSr to get +/- 7 ft accuracy most of the time outside. If your GPSr does not have WAAS reception turned on, turning it on will help out with the positional accuracy.
Weak batteries would not be the situation. I am sure that your unit would be screaming to be fed when necessary.
One thing about patch antennas. They have to be parallel to the ground to work the best. Any tilting and their performance degrades.
Hope this helps and now back to making dinner....
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Thanks for the reply, Itchyweed (and where did THAT handle originate?). Sounds like you've had a similar experience.
Have a good evening.
J.
I was given that nickname aeons ago in highschool and I do not remember by whom. I just like it and it has stay with me for years and years.
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For what it's worth, my eXplorist 200 began, two days ago, displaying two W icons (for WAAS stations), both in the SW (California-ish?) part of the satellite screen. The two W's were pretty much overlapping. Out of curiosity, I did a hard (complete) reset. At first, the W appeared in the SE (where it likely was when the unit was manufactured). Then, after a couple hours in the open, while I was inside at work, the W switched back to the W coast, and was joined by its nearly-superimposed secondary W.
Has any other Magellan user experienced similar displays the past couple of days?
Performance-wise, things are working fine. I typically get anywhere from 9-13 satellites locked, w/ 7'-16' accuracy here in N Minnesota. I'm just curious as to others' recent experience.
From Minnesota, the two W's in the southwest means that you are seeing good ol' 35 and 48. 51 is south and a bit west. I have the same pileup for both 35 and 48 here in Wisconsin.
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It ain't lack of incentive. Just no time. As the Old One is often quoted as saying, "Workin' on it."
"There is always time, Grasshopper."
If there always was time, why is it that I need 36 hour days to get an honest day's work done with some sleep thrown in?
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#48 was a no show in the morning drive at 7 am CST (13:00 UTC).
#35 was up alive and sending data. #51 was live but no data.
Oh, the agony of it all........
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I had asked this question to Garmin about what the distance is: either +/- 7 ft or +/- 3.5 ft. The answer was +/- 7. Well, 7ft is about 2 meters. Given what is being done and the instability of the whole system (crystal oscillators, mother nature, ionosphere, how many boo-boo's are on your hands, etc.), I'll take +/- 7 feet.
Of course, the more direct the correction signal is, the more accurate the corrections can be. Right now, we are at solar minimum. I would seriously doubt consistent locations at solar max when the ionosphere is doing fits, splits, and handsprings.
Since the GPSr is lining up data signals to get position, one could use the jitter to determine confidence. A lot of jitter would be a poor fix and little to no jitter would be great.
Since I can remote my antenna, me thinks I will put a monument in my front yard. Run the GPSr with its lights on to keep it warm and inside and do several six hour runs at the same location. This will be fun since I can see all three WAAS birds.
Also, it looks like two more days and 48 goes live....
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Just to be sure... Even with the news above, I still don't have to reset my GPSMAP 60Cx which came with chipset software 2.80? Is that correct?
If anyone could help with this (without trolling) I would appreciate it, thanks
HEre is the the listing of updates from Garmin and their website....
# Additional Software
* GPS Chipset Type G Ver. 2.70 as of Jul 19, 2006 Download
* USB Drivers Ver. 2.1 as of Aug 26, 2004 Download
* xImage Ver. 2.3 as of Mar 23, 2005 Download
# Unit Software
* GPSMAP 60Cx Ver. 3.00 as of Jul 19, 2006 Download
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I would say that there is no need to update.
I know the updates (I frequent that page often, I'm waiting for them to get up to date with my GPS since I have a later version [2.80] then they offer ;-).
I am wondering if a full reset will help my unit.
It won't hurt the unit. It will be like starting up a brand new unit.
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Just to be sure... Even with the news above, I still don't have to reset my GPSMAP 60Cx which came with chipset software 2.80? Is that correct?
If anyone could help with this (without trolling) I would appreciate it, thanks
HEre is the the listing of updates from Garmin and their website....
# Additional Software
* GPS Chipset Type G Ver. 2.70 as of Jul 19, 2006 Download
* USB Drivers Ver. 2.1 as of Aug 26, 2004 Download
* xImage Ver. 2.3 as of Mar 23, 2005 Download
# Unit Software
* GPSMAP 60Cx Ver. 3.00 as of Jul 19, 2006 Download
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I would say that there is no need to update.
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This is from www.nstb.tc.faa.gov:
New WAAS GEO Status as of 10/30/06
INTELSAT(PanAmSat), Galaxy-15, W133 deg, PRN -135 (48)
PRN-135 is currently in the process of being switched into the operational WAAS.
The current plan is take PRN-135 out of Message Type Zero Test Mode and
place it into normal operation on 11/3/06 about 08:00 UTC.
Once officially operational, PRN-135 status will no longer be provided by this
non-operational web site.
PRN-135 will operate for about the first 6 to 9 months as a data link of correction
and integrity information only. That is, the UDRE will be set to "not monitored".
This will result in it being displayed with a "hollow bar" on some receiver displays.
The ranging control loop for PRN-135 will be running, but the WAAS ground system
will not provide UDREs smaller than Not Monitored until the FAA's verification of
the integrity analyses for the ranging function have been completed as part of the
PRN-138 testing. (Data link only operation allowed the PRN-135 deployment to be
accelerated to compensate for the loss of PRN-122 in the North East)
Just to be sure... Even with the news above, I still don't have to reset my GPSMAP 60Cx which came with chipset software 2.80? Is that correct?
Why worry about it if your gps is working properly?
My computer is working properly, should I not update Windows and other programs?
No one in this thread -needs- to do a full reset to get the new WAAS satellites, all of their units were working properly. Why did you wait until the 3rd page to give me crap about it??? Why not ask the other 103 people who posted to this thread why they are worried about it?
Even though today is Halloween and there are people wearing bent noses out there, we do not need them here.
My mind is fried from work but here goes. Some units have to have their almanacs cleared and reloaded from the sats. My GPS V is that way, methinks. So, in order to see the new WAAS birds, I had to prevent it from seeing 35 and being satisfied with that. That is why I started this thread. Now the GPSr can use all three WAAS birds and pick and choose.
Since this thread has evolved, there has been topic that some newer units have firmware coded almanacs. IMHO, a hindrance and a pain from this geek's point of view. This may require some units to have firmware upgrades. I realize that may make the units turn on quicker, but once the almanac is in, you are good to go. I do not know which versions of software, which manufacturers, or models need to load new software to work with the new birds.
IMO, the manufacturers should be posting on their websites in a reasonable place whether or not your particular model needs new software burned in. Maybe someone can post a spreadsheet on which of the newer firmware fixed units need upgrading.
Now back to my next adventure...figuring out how accurate my GPS V can be from the binary data stream......
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This is from www.nstb.tc.faa.gov:
New WAAS GEO Status as of 10/30/06
INTELSAT(PanAmSat), Galaxy-15, W133 deg, PRN -135 (48)
PRN-135 is currently in the process of being switched into the operational WAAS.
The current plan is take PRN-135 out of Message Type Zero Test Mode and
place it into normal operation on 11/3/06 about 08:00 UTC.
Once officially operational, PRN-135 status will no longer be provided by this
non-operational web site.
PRN-135 will operate for about the first 6 to 9 months as a data link of correction
and integrity information only. That is, the UDRE will be set to "not monitored".
This will result in it being displayed with a "hollow bar" on some receiver displays.
The ranging control loop for PRN-135 will be running, but the WAAS ground system
will not provide UDREs smaller than Not Monitored until the FAA's verification of
the integrity analyses for the ranging function have been completed as part of the
PRN-138 testing. (Data link only operation allowed the PRN-135 deployment to be
accelerated to compensate for the loss of PRN-122 in the North East)
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If you were trying on Saturday, 28 Oct, for some reason WAAS coverage was very spotty. Both of the new birds in testing were not on line, that I could see outside. New England will have a devil of a time picking up 35. When 48 & 51 stay stable. NE should have no issues.
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Just got in !!!!!
Yippee!!!!!
Ah, the euphoria is short lived....
Gone again....
sniff.....
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Just got in !!!!!
Yippee!!!!!
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The 20 channel receiver is interesting to say the least, considering you can't see more than half of the constellation at one and the WAAS birds.
But this brings up something that I read in a trade rag. A chip company has come out with a GPS receiver chip that will pick up the NAVSTAR/GPS, GLONASS, and GALILEO satellites, all at once.
This may get fun in the future...
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I did the reset on my Legend Cx running V 2.6, blocked it from getting 33 and 35 and as it scrolls through the sats it hits 46 then jumps to 49, then 50 and right back to 35 without even trying to find 48 or 51. The reset I did is as per Garmins instructions. Hold down page and enter while powering up, answer yes to "are you sure" , enable waas before uncovering antenna, block 35 (which I don't get often anyway) and still nothing. Am I missing something? Anyone else with a Legend Cx having any luck?48 and 51 have been cycling on and off lately. Cutover to 48 going active is supposed to start 2006-OCT-23. Of course, this is a tentative date and is subject to rearrangement. There still is no word on when 51 will go live at this time either.
Give it a couple of days and try again.
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If I'm already seeing 48 and 51 and am getting "Ds", is there any reason for me to go through the hard reset?
If you see active bars on either 48 and/or 51 and are getting the "D's", don't bother. Your almanac is updated and ready.
Good Luck!
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Looks like #48 won't come on line until 2006-OCT-23.
"I am from The Government. I am here to help you."
Still no word on a tentative commissioning date for #51.
Further testing before releasing to increase confidence in the birds is alway prudent and desirable.
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I have a GPS V and the manual states two things: temp range is 5 F to 158 F and to use Lithium batteries when in below freezing temperatures.
I would love to go out GPS'ing during the winter but I had frostbite in both of my hands from many, many years ago so I have problems with them functioning when it gets cold.
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This is the same issue that our cars face in the cold months. As the temps go down, starting energy demands increase and the capacity to deliver energy declines. It is the same with batteries for our GPSr. Lithium batteries have better cold temp operating abilities than do alkalines. Now we can get technical here on this but that is not the intention here. Also too, is the total energy capacity of the different technologies as well that can come into play here.
I use an external power cable and a small lead-acid AGM battery. There are some that are able to be fitted into coat pockets. Asides from the inconvienence of the leash, I can be on for hours in the cold. The battery that I use is 12 volts @ 18 A/H (hey, it was free). I use 1.2v 2.5 A/H NiMH in there. If I assume 200 mA draw. the AA's will last about 12 hours. The unit can draw 1.5 watts out of the big battery. That would last about 140 hours. Mind you, the numbers are on paper and YMMV.
One other issue to be aware of and that is getting the LCD panel too cold. They can crack and die or become fragile as it gets colder. So don't drop the unit when cold. The display may not survive a drop.
I did the reset on my Legend Cx running V 2.6, blocked it from getting 33 and 35 and as it scrolls through the sats it hits 46 then jumps to 49, then 50 and right back to 35 without even trying to find 48 or 51. The reset I did is as per Garmins instructions. Hold down page and enter while powering up, answer yes to "are you sure" , enable waas before uncovering antenna, block 35 (which I don't get often anyway) and still nothing. Am I missing something? Anyone else with a Legend Cx having any luck?
Not very accurate GPS - help!
in GPS technology and devices
Posted
A calculator and a GPSr are two completely different animals. The calculator is a device that does not rely on a precision clock to function and get the correct answers. The faster the clock, the faster the answers appear and vice versa. Clock speed does not affect the answer.
The clock in a GPSr has to be stable in order to display its location accurately. If the crystal clock inside the GPSr is drifting up and down, your position will be unstable. Mind you, the atmosphere has a big role in making the numbers unstable but there is no need for more sources of instability.
I use my GPSr for "amateur surveying" of benchmarks and when I am going to do a benchmark run, I keep it on for 24 hours preceding so that the unit is as stable as it can be. Using the GPS V and its built-in antenna and a 45 minute run, I can get post-processed results of +/- 0.5 meter.