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itchytweed

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Everything posted by itchytweed

  1. I don't think it really matters which WAAS satellite you are seeing or if you are even receiving WAAS corrections. WAAS on my eXplorist 400 doesn't seem to improve my accuracy at all, just stability. I have no trouble finding caches without WAAS. I don't care either way. If my GPSr is getting corrections, all the better. If not, no biggie. If you are seeing plenty of regular GPS satellites you will be just fine. Check out this reply from Peter in another topic about Garmin's satellite numbers versus Magellan's Ws. Got to agree with you. I have the 76csx and always have at least 5 birds showing Ds. Don't see the reason of obsessing over connecting to 51. Sometimes mine does sometimes it doesn't. I don't need pinpoint accurcy. 15ft of accuracy seems good enough for me. I'm not knocking anyone here btw, just trying to understand it. I don't think that you are knocking accuracy. On some systems, they will not scan for the new WAAS birds unless the almanac is wiped and reloaded. Of course, on the east coast and midwest, getting the new birds that are higher up than 35 is a benefit (easier and more reliable reception) for people to use WAAS. The more birds you can use, the better the reliability, especially under the defoliating trees. Now to clean up the remains of dinner. For all of us who are in the south, midwest and east, stay dry and warm.
  2. I believe that the way that you do a "soft" reset, for lack of a better term, is to tell the unit via the menus that you are in a new location. Others with Explorist's have done that and reported some success in other message threads here. Just tell it that you are in a new location and hopefully this will do it. This does not preclude the possibility that your software may not be programmed to allow for reception of the new birds.
  3. 48 appeared to be sending correction data. 51 was not responding - no bar, no data. Oooohhhh, the anticipation of it all
  4. You should be able to see three birds from your location, 35, 48. and 51. After resetting the GPSr, you have to leave it still for about 45 minutes to an hour to let it crunch. AFAIK, 36 is not an assigned satellite. This may be showing up because the software is doing an ID scan checking for new satellites broadcasting the correct code. It may be possible that you did not leave it long enough on to cycle through all the WAAS numbers. IIRC, 35 is not broadcasting an almanac for 48 and 51 until they get commissioned. 51 is sending data but 48 isn't - that was this morning into work. If acquired, 48 and 51 would show up. On my GPS V, I get a strong gray bar on 48 (no usable data but signal) and a black bar on 51 (usable data). The D's mean that the GPSr has received valid compensation data from the WAAS birds for that particular satellite in your constellation and is applying the corrections to the received data. The D will disappear when the data gets too old and no new correction data has been received and applied. I don't think you did anything wrong. I would think that you just did not give the unit enough time to cycle through all the numbers to find out what it can hear. That number 36 should scroll upwards every few minutes and the unit should record what it hears. Good Luck!
  5. I looked at the Explorist book and there are no setting on/off for WAAS. All I can think of is that you may want to try RESTART GPS. Maybe someone else may be able to offer a better suggestion.
  6. Battery Saver On? WAAS reception off? You should be seeing them all from Texas. Hmmmmm..... sorry for double posting...server error
  7. Battery Saver On? WAAS reception off? You should be seeing them all from Texas. Hmmmmm.....
  8. Significant is a not terribly defined answer. Niether do I take that as true untill I see figures. My take is that it uses some more juice but not nearly as much as backlight and autorouting. I never considered Michigan that far east. You have had good WAAS coverage all along. It is Maine the hasn't. The launches happened about a year ago. #48 is to go off test mode on 10/11/06 and should be good to go shortly after, puting the Maine area back into play. WAAS 51 was sending data this past weekend and yesterday. WAAS 48 was tone only and no data. The east coast should be seeing 51 with no problems. Also, 51 should go operational in a couple of day, IIRC.
  9. I prefer to use DD.DDDDD mode all the time. I will even convert ddmm.mmmm and dms to dd.ddddd. The idea of doing the property survey has run across my mind but I live in the middle of four regional planning commission benchmarks. A project of mine is to rent a total station for a day and do a proper survey using the marks as my reference points. I am not a land surveyor, by trade, but I remember enough from college to do the deed. I had to learn how to do surveys in snowstorms using plain transits, philly rods, and tape. Today I did a cache and even though I knew where the cache was, my GPSr called it on the walk to within 1/2 - 1 meter. I can't complain about that at all. I need to pop my eyes out, give my head a rest, and go to sleep. Monday comes far quicker than I like. QRT de N6NKO
  10. Let me start by saying that this was an exercise from the engineer side of me. Almost everyone has heard the gag line "Measure with a micrometer, mark with chalk, and whack with an axe." I decided to take that outlook when looking at the precisions presented by my GPS V. The unit present four different data formats, three are on-screen, one is not. The available on-screen displays are DDD.DDDDD, DDD MM.MMM, and DD MM SS.S. The one that is not is the NMEA output which is DD MM.MMMM. There are other data modes, simple text and binary, but I will not go into those here. All the below data is using WGS84 scalings. The base location for these calculations are N 43 01 00.00000 W 88 01 00.00000 (dms). Here are the results: DD.DDDDD +/- 0.00001 deg lat = +/- 1.11 meters +/- 0.00001 deg lon = +/- 0.816 meters DD MM.MMM +/- 0.001 min lat = +/- 1.854 meters +/- 0.001 min lon = +/- 1.355 meters DD MM SS.S +/- 0.1 sec lat = +/- 3.086 meters +/- 0.1 sec lon = +/- 2.265 meters NMEA DD MM.MMMM +/- 0.0001 min lat = +/- 0.19 meters +/- 0.0001 min lon = +/- 0.134 meters These are the displayed accuracies. But a chain is no stronger than its weakest link, and it really applies here. Ionospheric variation, temperature calibrations, reflections, component accuracy, etc. Since GPS is a timing dependent operation, stability is of the utmost. The nice thing about digital operation is that the functions and results are repeatable. The best way to improve the stability of the unit is to stabilize the master oscillator. This is why temperature correction data is included in the units. Problem is as the unit ages, these corrections have to be adjusted. As an example, I have a HF Amateur Radio receiver that will tune down to 1 Hz accuracy. I can hear when the oscillator has drifted. Even though the unit is left on all the time and in a stable temperature environment, the Temperature Compensated Crystal Oscillator (TCXO) will drift. It may not drift as far as an uncompensated oscillator but it drifts. An OCXO (oven controlled) would be even more stable but at the expense of a larger unit, higher power consumption and longer times to stabilize. Now that begs the question, does the drift in the oscillator cause a position shift greater than the accuracy of the processing? Hopefully, the shifts are within the least significant digit. This is just food for thought.
  11. I would call this into question. If the WAAS processing was turned off in battery save mode, I would at least expect the WAAS selection box to show "Disabled" or blacked out. In the satellite window in Bat Save, the slots for the WAAS birds are gone but it looks like it may still be crunching on something. The current really did not drop until I explicitly disables WAAS in Bat Save mode.
  12. 48 is broadcasting tone but no data. 51 is sending out tone and data. I was picking up 51 here with no problems during a test and even in the house in the kitchen.
  13. Considering where this thread is going, I thought that I would run a test with my GPS V as the guinea pig. I hooked it up to an external battery ( 12 volts, 18 A-H ) with an ammeter in line. Here is what I got with a battery voltage of 13.5, FWIW: WAAS on, Bat Saver off: 50-55 mA, max 0.74 watts WAAS off, Bat Saver off: 49-52 mA, max. 0.70 watts WAAS on, Bat Saver on: 50-53 mA, max. 0.72 watts WAAS off, Bat Saver on: 48-50 mA, max 0.68 watts The current was going up and down in regular cycles. That is why the range in currents. I do not have peak hold on my old Fluke meter (sniff, sniff). I had at least one WAAS bird and about 8 active regulars while doing this test. Now here is the real battery eater combination - WAAS on, Bat Saver off, Full backlighting: 203-217 mA, max 3 watts. Now lets bring that down to battery levels. I am not taking in to consideration losses in power conversion. I run Ni-MH batteries. Total voltage is 4.8 available. At 0.74 watts, I am pulling about 150 mA out of the batteries. At full light , 3 watts, I would be pulling approx. 625 mA. At 0.68 watts, I would be pulling approx. 140 mA. 2500/140 = 17.8, 2500/150 = 16.6, 2500/625 = 4. The 2500 is from the capacity of my batteries. The times listed above are not accurate but representative. The unit does save energy with WAAS off vs. on. The backlighting is a real killer though. Of course, YMMV....
  14. I believe that every GPS out there that is WAAS capable has the ability to turn it on and off. Some are more convienient than others. Handheld and dash units should be easy. Dongles, well, that is a different story. You have to send the command to turn on or off. There are pro's and con's to using WAAS. The idea of WAAS was to help aircraft navigate. WAAS is actually sponsored by the FAA, IIRC. The idea of putting up the new WAAS birds is to allow aircraft to use GPS for landing purposes. So the biggest pro is increased accuracy. The WAAS system relay "ground truth" correction information to the GPS units via the WAAS sites. The correction sites all over the US relay information back to their processing system which generates the location correction data and sends it out. The GPSr then take this data and applies it to what it is receiving and tries to come up with corrected information. How accurate will it be? Who knows? The ionosphere is a dynamic beast at best and can really mess things up as well depending how disturbed it is. That is a subject for another thread altogether... But, to sum it up, WAAS is being implemented to allow for improved accuracy of the Consumer GPS market. Now comes the con - increase power to process the information results in shorter battery life. Some books for GPSr's shows the estimated battery life with and without WAAS activated. I am sure that there may be a line in the specs for the unit that mentions battery life with/without WAAS activated. Hopefully this helps out. I am sure that others will put in what I have missed.
  15. Thanks for the correction. I am still curious though about a comparison between the two. Now back out to yardwork (leaves, leaves, and more leaves). This time of the year is a beauty (the looks of the leaves changing) and a beast (having to clean them up).
  16. DiS02, When you get your new Legend when you turn "30", compare the two for site accuracy, lockup time, etc. I am beginning to wonder if Garmin may have taken two steps back by resorting to the SiRF products with patch antennas instead of staying with their receiver and quadrifilar antennas. I just got over the "bug" that it was brought home from school by the kids. Had the effects for about three weeks. Yuck! So get better.
  17. The +/- refers to a radius. There is a 95% probability that your true position is somewhere within a 7 foot radius of the physical location you are actually at. Within that circle (technically an elipse, I believe) there is an equal 95% probability that you are standing at the true position or you are 14 feet away from it. The reported accuracy from the unit is more of a relative measure than an absolute. Just got the reply back from Garmin. The accuracy is radius ... sniff, sniff Regardless, I will take it and run. I can't complain about +/- 7 feet at all. Just knowing what they mean helps out immensely. Now, back to lunch.....
  18. If you have a DMM, just turn the GPSr off and route the battery path through the ammeter terminals and see if you are getting current flow. You may see a hair of flow to operate the on/off switch circuit. Then compare that flow to what you read when the unit is on. Also, fast charging may bring the terminal voltage up to a useful level but the battery has not had time to absorb the charge. The chemistry can only convert so fast. I prefer normal desk chargers and keep several Ni-MH sets available - one in, one out and two in the charger on trickle. The sets are always rotated to keep them charged. Good Luck.
  19. These are not NGS BM's. They were laid by the Regional Planning Commission and are measured (hopefully as they measure to +/- 0.005 ft) as they are used as references for real estate control and planning. The issue that I have with them is that they used Easting/Northing in survey feet measured to 0.01 foot. So I had to convert them to Lat/Lon using NGS software. The real twist is that these are every 1/2 mile in square grid and as luck has it, all the monuments lie in the center of very busy intersections. The whole process will be challenging to do solo and probably the time that I will have available to do the work will be in the winter and on a day that it is snowing heavily :-) All I need to do is rent a total station and two retroreflectors and I can do the measurements in one shot turning one common corner that is at about 90 degrees. Plus, I can also fill in the blanks on my property deed as well. The description is lot/block and has never been really surveyed. Such Fun!!!
  20. I would suggest that you put the GPSr on a tripod or something of that nature to minimize ground reflections. Where I live, I am surrounded by four benchmarks. One is 1/2 mile from me. A project that I have in mind is to rent some surveying equipment and apply what I learned in college aeons ago in my surveying class and extend the BM to my place and put in a marker to reflect that. Then the marker can be used for calibration checks. Before doing the readings, I would let the unit run for about three hours. This will warm up the electronics and stabilize the internal oscillator better. This will allow for a more reasonable and accurate reading. Good Luck!!!
  21. Unfortunately, I am not happy about the demise of the GPS V. The unit was widely functional and versatile for many tasks. Sniff, sniff, hanky....(Roger Rabbit sound) Just to let everyone know, the unit can hold 7ft accuracy while moving. That is good in my book. Now to find out from Garmin if the accuracy means +/- 7 ft at your location or +/- 3.5 feet at your location. I think that it would really be righteous if it ends up meaning +/- 3.5 feet (~ 1 meter). Lost benchmarks, here I come!!!
  22. If you have the 60Cx or 60CSx it is already WAAS compliant, but ships with default to Disabled. To Enable WAAS, do the following from the satellite page: MENU MENU SETUP SYSTEM WAAS / EGNOS (2nd menu option down) ENTER ENABLED QUIT / QUIT I was seeing 51 today on my way to work today with my 60CSx with reported accuracy of +/- 13ft In my experience I either get Ds on most of the satellites, or no Ds at all, and they tend to come and go. This is true for both my GPS V and 60CSx. I don't understand what that is all about, perhaps someone who understands the technical aspects of WAAS can explain it. For a good explanation of WAAS, go to http://gps.faa.gov. There is a good explanation to WAAS there. The dropouts are caused mostly by garbled reception. If the WAAS birds are intermittent in reception, the correction data being sent will be intermittent as well and when the correction packet expires, the "D" drops out. The GPSr then has to wait for the next valid packet to start correcting all over again. Having more than one WAAS bird available helps ensure a consistent flow of correction data. Hope this helps....
  23. Check your menu options. There is a option probably to turn on WAAS processing and the unit should not be in battery saving mode as well. Then you should see the birds.
  24. Here is how I pulled this off... From previous knowledge, I know that my GPS V can't see 35 in its new position from my parking space at work (third spot from front door) as I park facing east. I mount the GPSr on the dash in the center. The high angle of the Jeep Cherokee front window and the location on the dash cuts out almost everything in the western hemispheric view. Since 35 is low in the western sky for me, any signal from it is intercepted by my car roof (metal) and the GPSr is deaf to it. Plus, the side windows are metal passivated as well. Now I did the almanac reset and left the unit on the dash while eating lunch in the car and watching the satellite info screen. When I saw the unit cycling through the WAAS numbers, I knew all I had to do is wait. When it locked onto 48, another WAAS channel popped up and continued scanning up. Then it locked onto 51. After the 51 lock in, 48 went gray and the GPSr started crunching the data from 51 and springing up D's all over the place. The accuracy went from 3D 45 feet to 3D Differential 7 feet in about 3 minutes time. SUCCESS!!! The unit now uses 51 as primary, 48 as secondary and 35 when all else fails. So, you have to rig up some form of metal shield to block the satellite. If at home outside, a metal cookie sheet should do the task just fine. Just set up the unit in satellite view mode, adjust to block reception of the west, reset the almanac, have a cold one and watch the updating take place.
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