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Everything posted by Kerry.

  1. As opposed to the CORS type antenna above there somewhere a dGPS antenna setup could/might look like the following (which is an actual dGPS antenna setup). everybody keeps telling me where to go
  2. No CORS (or equiv) don't really have a direct/continuous relationship to dGPS sites but depending on how the reference sites were fixed CORS could have been used to initially do that. CORS sites and data generally are higher up the tree then dGPS sites and within CORS (type) sites there's basically different hierarchical levels. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  3. They've also been into the virtual removable fence that's not a fence. GPS tagged cattle and the fence basically is a series of waypoints uploaded/changed to the tags as required via a radio link. The cattle approach the invisible fence, get a bit of a jolt and turn back. Probably expensive but for a few thousand head. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  4. I think you've got the bull by the tail. Not to sure if you're really looking for help from all the majority of that. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  5. Start with the obvious, more than a 100m tends to indicate Datum and/or position format. Eliminate both of those as a possible cause first. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  6. Anders, I knew you would, when we're finished with the sun today we'll let you have it for the next few hours, as long as you promise to send it back tomorrow. But really day v night doesn't have a great concernable effect on accuracy, accuracy that is going to be a real issue anyway in these circles, unless of course you're using differential then there can be some issues just after the sun goes down. The solar flux is the main villan and it's on about a 11 year cyle between peaks/max. Peaked back in about 2000 so things can only get better. At least for the next 3 or 4 so years Catch ya again when the sun comes back . Cheers, Kerry. I never get lost everybody keeps telling me where to go
  7. I don't think it was mentioned that the GPS knew which way you are/were pointing (it can't) just that if you were "pointed" directly to where you wanted to go and being pushed sideways then one would have to steer a course to counteract that and give you the most efficent way to stay on course to your destination. The GPS knows where you started from, where you wanted to go. It also knows where you currently are and heading (not pointing), which isn't really a heading as it's based on past information (sometimes referred to as Course Over Ground) but it's close enough (but still technically doesn't tell you a heading) given the time frames. Similar with Speed and Velocity Made Good as if one was heading directly to the destination with no influences then speed and VMG is the same. But with wind/current influences then your speed is different to your VMG and if one was going sideways (at a certain Speed & Course over Ground) then VMG to the destination is almost zero (or even negative). Cheers, Kerry. I never get lost everybody keeps telling me where to go
  8. Poindexter, yeah it's interesting in just who provides user definable masks and who doesn't. Maybe it's a good query to put to some of the manufacturers who don't allow this function. Maybe they don't want to make it sound confusing, maybe there's this wider community myth that the more satellites a receiever sees/uses, the better it is, more is best type syndrome even if Sats are contributing anything constructive (sometimes destructive) to the solution. Lowrance was originally 10 degrees, I'm intersted in what they are now as well. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  9. .... and solar flux (Anders I'll let you slide with sunshine, for now ) interactions with the earth's magnetic field and electron count (gradient density) contributing to errors in the single-frequency model .... nobody has much control over these. With the worst 2 satellites removed the "conservative" SPS accuracy "on the ground" using a single freq receiver under standard conditions (no obstructions etc) is 33 metres @ 95%. With the mixture of satellite technology (and ages) now up there and the differing User Range Errors that some of these Sats exhibit some of the accuracy "expectations" and claims by some are rather interesting (to say the least). Cheers, Kerry. I never get lost everybody keeps telling me where to go
  10. RRick, not going to be of concern to Geocaching (directly) but this "movement" thing might become more of an issue than most people think. Your driveway might be moving 1/8" per year but some countries are moving 3" (or more per year) and based on fixed time frame references in a few more years when things have moved forward a bit more and technology has moved back a bit, basically the accuracy of the (then) normal common garden variety receiver will/should be able be detect this overall movement (since fixed). It's a daunting issue for some applications. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  11. Could we have some indications of what the mask cut-off angles for different receivers might be. Do have values for many receivers but in addition would appreciate the make/model, software version, mask angle and the method that angle was determined. The actual method used to determine the cut-off is important. WAAS has obviously changed many manufacturer's thinking with regard the application of mask angle parameters. Mask cut-off angles were also re-accessed recently on an international basis as far as differential systems are concerned. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  12. Hopscotch, I don't have any real issues with Hiemdahl either but you appear another lost soul in a field that I'm not sure you understand either as you've also lost complete track of the original query. Try going back to the beginning and read the original query again (maybe twice). quote:Any tips on how to get consistent readings would be appreciated. To answer your query you basically can't (averaging now just can't wait for that as an answer), that's simply (sort of) the way it is with a SPS receiver BUT you can make the most of what there is with some planning AND understanding BUT you've chose to dismiss those comments. Cheers, Kerry. I never get lost everybody keeps telling me where to go [This message was edited by Kerry on April 23, 2003 at 03:00 PM.]
  13. With no outside/zero affects both will be the same. Generally applies in aviation or boating situations. However in a current/wind situation the "Course to Steer" is that as it is affected by the current/wind etc component. In simple terms from your present position the "to course" might be due north (0 degrees) but if the current is running to the west then the "course to steer" will be somewhere east of north depending on the amount of currect. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  14. quote:Originally posted by Anders:Just in case you want a real-life example of when "time of day" matters, check http://www.geocaching.com/seek/cache_details.aspx?ID=41685 Look at the (at this moment) last log, when I visited the place. Anders, was just reading a request from a GIS user locating "street furniture" in a city/high rise area. Not only was he wanting to be in the right place at the best time (or is that best time for a specific location) but on a real-time/position in the street basis. In other words apart from the dynamics of the system there is also the requirement of position in the street and one might imagine just stepping sideways could/might be enough to change the whole scenario. Mission planning on the time-line in real time, it has some interesting "problems" to say the least. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  15. Peter, I'll leave you explain the english language if it makes things sound correct. So is "Time of day" and "Times of day" different. Today might be April 23, 2003 but in GPS terms it is Day of Year (DOY) 113. Is "Day Of Year" as used in all almanac/rinex references incorrect? Also GPS time for specific purposes is referred to as "Time Of Week", which is in seconds starting midnight, Saturday. This TOW resets every week, is "Time Of Week" incorrect do you think? These TOW (Time Of Week) and DOY (Day Of Year) abbrev's are all standard GPS terms just like TOD (Time Of Day). Does appear we're talking about the same thing thou, even if the english might not be what some expect, it's all GPS language. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  16. quote:Originally posted by peter:I would call it what it is - i.e. that due to a number of factors, i.e. satellite positions, placement of obstructions, satellite availability, etc. the expected accuracy of a GPS measurement will vary over time. I'm not sure I'd call it "vary over time" but maybe a better term is "flucuate over time" (sometimes can fluctuate from good to completely bad). But what your saying in that is, there's times thoughout the day that are better than others? right. Doesn't that translate into the "Time of Day" does/can matter? quote:When you say that this is a "time of day" effect then I would ask at what times of day you'd expect the best result and the answer would be that there is no one good "time of day" because a good time one day will be a bad time on another day. You can work out the satellite positions for a specific location and predict relatively good times to do GPS survey work there, but they won't be at specific "times of day" - they'll just be a set of times for that location. I don't believe the word "specific" (that's your terms) has anything to do with the comment that "Time of day" matters. Again what you've just said in that is that certain times of the day will/can be better than other periods/times throughout the day, correct?. Doesn't that translate into that "Time of Day" does/can matter? quote:Similar with GPS reception, it's not the "time of day" that's important, but rather the satellite availability, positioning, and obstructions. Certainly these will vary with time, but they aren't tied to the "time of day" except to the extent that due to the synchronization of the orbits to sidereal time the satellite positions will repeat at about the same time for a number of days (with a slow drift due to solar vs. sidereal timing). Gee, I wouldn't compare GPS availability and all that stuff with planting crops, really can't see any comparision in that what so ever. Leave that to the long range weather forcasters. And isn't it all that satellite availability, obstructions, positioning etc that will dictate exactly when the "best" times will be on a particular day. Doesn't that translate into "Time of Day" does/can matter if one wants/expects the best results. My initial comment was that "Time of Day" can matter, and it does, but no where have I got into this "specific Time of Day" as specifics times have nothing to do with anything. As for the orbit precession timing difference (~4 minutes per day) that's not really a major influencing factor when compared to the real issues. All that you've mentioned has basically said that reception under certain conditions will be better at certain "Times of day" than other times. I don't have a problem with that as that's exactly what can occur. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  17. Not finished yet The following is the same backyard (today) and just for the fun of it SVN25 (PRN25) has been made unavailable (like if it was on maintainence, which can/could/might easily happen). The difference 25 makes is totally around that 6-7am time frame. But also some might note things have changed (for the worse) around 2pm, which is totally and solely due to being a couple of days apart (all based on the same current almanac). I'll pose the question this way. If "Time of Day" doesn't matter then why would it be so that's there absolutely no chance of getting a position at this particular location at ANY time today. In other words if time of day doesn't matter then one would "expect" to get a position fix at this location, under these circumstances at ANY time over ANY 24 hour period. everybody keeps telling me where to go
  18. quote:Originally posted by junglehair:Wow, this is the most rediculous discussion I have seen on the forums to date .... (Kerry, I'd be interested in hearing what you do for a living and why you know so much about GPS). Lets just say GPS and what I do for a living has a fairly close connection (and that's any time of day ). All types for all purposes a GPS is basically a GPS and there's some fairly fundamental principles that apply regardless of the type or use. And for sure one thing that stands out from time to time is some of the absolute miss-informed myth's that get propagated by the "applicance" sales types. Realize this is getting off the topic but it might also shock some to find out that in straight SPS mode there's practically bugga all difference (in practical SPS accuracy) between the normal run of the mill $400 handheld and a $40,000 "survey grade" receiver. For your info those plots above are based on a 5 degree mask angle as ideally NO receiver should really use low horizon satellites. Some manufacturers run a 0 (zero) mask, other a few degrees, some even 10 degrees. Most who use recreational units wouldn't have a clue what mask angle their receiver is anyway. That 15 degree for geodetic stuff cut-off basically ensures the best possible signal data is used and not corrupted with suspect obs from the lower horizon, more atmospheric influenced signal. But these days with sky clear above 15 degrees things aren't all that bad but of course there's certainly been times (even lately) when one may as well pack up and go home. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  19. Peter, this "Time of Day" issue (certainly wouldn't call it "specific" but) is a generic one and for sure there many variables, which go into affecting this. The atmospherics and much of that similar type of stuff is generally untouchable, nobody has all that much control if sun spot activity will be a problem today, tomorrow or whenever. This type of issue is dependent on many things like location, obstructions and apart from other things just what the system is actually doing at the time. All things aren't the same for all locations all of the time but depending on circumstances there can be issues some of the time and these times (all things being equal) are basically predictable. This "Time of Day" issue doesn't target or favour geocaching or any other use of the system as there is basically only one system. One has to understand the whole system, including the users are dynamic and for sure what occured here this morning at what ever time isn't "exactly" occuring anywhere else either but that's simply a factor of a specific user's environmenet in relation to the constellation at a particular time. Come back to the same point at some other time and obviously things have changed as if they didn't then GPS wouldn't work. Basically if users are unable to grasp this principle that the whole system and the relationship of that system to the user is constantly changing then there is some definite miss-understanding. First there has to be this understanding that if at a particular time at a certain location due to several variables a user doesn't have enough satellites to get a position fix but can come back after a short period and there is enough satellites then if time of day doesn't matter then I'd like to know what tag some call it. Gee, there's so many variables involved here, apart from the atmospherics issues, different satellites are on maintainence almost everyday, users are another, different locations. Even though there is some "basic" consistency in the constellation, really NOTHING stays the same, especially the user. That also one reason why the current accuracy specifications (oh by the way these accuracy specs apply to ALL users, geocaching isn't singled out as being special either, geocachers are simply just "another" user) are based on Signal-In-Space specifications as that's what's the owners/operators of the system have most (some) control over. They don't have any control over how/when/where or why a user wants/expects their equipment to work and under what conditions. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  20. quote:Originally posted by Johnnyvegas:This is a geocaching NG. Not one dedicated to GPS issues. It would seem you seem to think you know about goecaching, though you have never treid it. Would you go to a doctor that has only read some books, with no real experiance. In my opinion you are a troll, and I have to time for you. Your a laugh Cheers, Kerry. I never get lost everybody keeps telling me where to go
  21. JohnnyVeges What an utter load of waffle and totally irrelevent credibility attempt. But this is generally the avenue some will take when their own credibility is on the line, don't have any answers and couldn't argue their own way out of the corner in a blue fit. Some advice Johnny, try and support your own credibility first before you attempt to attack other's about who you know absolutely nothing about. If I was you, I'd first get my facts right before making stupid statements. Actually I didn't know it is a prerequisite to hide and find things before one knows what they are on about . Really not sure what your thinking is behind that one but your starting to sound like your beginning to know more and more about less and less. It's been obvious almost from the start that you wouldn't know reality if you fell over it, as for experience well say on more. So far your comments and lack of ability to backup any of your "experience" apart from just because "YOU" haven't seen things means absolute ziltch in the real world. Oh and Johnny what has knowing/not knowing anything specifically about geocaching (as you ignorantly put it) got to do with what the subject of this post is all about. Get back on the subject, support your comments or simply sit down, shutup, listen and you might actually gain something new. At least if your going to make a comment then support that comment as otherwise simply because "YOU" haven't experienced or don't understand it or didn't know it was an issue has no relevence to what actually happens. As for "Time Of Day" NOT being an issue (in your own "experience") then your comments are absolute rubbish lacking any credibility or understanding of the system what so ever. And it doesn't require one to be a "geocacher" to know, understand or have some background on that one, it's simple fundamental basics that most who use the system should at least understand or in your case try to understand. Accuracy well that's another subject but that's also another favourite of mine and also averaging so feel free to bring anything up anytime you like. Just come prepared with the facts. You had a typical "real world" example put before you, now if you refute that then lets hear the reasoning and justification. Oh because "you" haven't seen or experienced that is irrelevent. Cheers, Kerry. I never get lost everybody keeps telling me where to go [This message was edited by Kerry on April 22, 2003 at 07:17 PM.]
  22. quote:Originally posted by Johnnyvegas:As I have said. For geocacing and recreational use, Time of day in not an issue. Then if it's not an issue you still haven't explained/outlined WHY it's not an issue apart from "As I have said", which says absolutely nothing apart from an obvious lack of understanding. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  23. While JV is organising some facts that TOD isn't an issue maybe others might be interested in these FACTS and PERSPECTIVE compared to some of the myth and miss-information. . Would probably also be a similar cry at around 2.30pm (+/- 20 minutes), 6.15am, 6.45pm and possibly those times with only 4 sats? (especially in conjunction with high PDOP's) And it basically would have made no difference regardless of the receiver type being used, no signals, obstructed signals is basically no signals, obstructed signals to all/any receivers. I'm not sure about some but most should be able to see there's certain times of the day when trying to fix a position in my backyard today is totally a waste of time. Not being able to shift/move the obstructions (as in the real world) then the other options are pack up and shift somewhere else (with possible better visibility etc) or observe at a "Time of Day" when conditions are better (best). That time is when the grey area (number of satellites are the highest and the red line (PDOP) is the lowest. Then on top of all this more location/physical stuff, which is real and can actually be analyized there's other issues/unknowns, which can be rather difficult (in practice) to take into account. Cheers, Kerry. Maleki you might recognize the software these plots come from I never get lost everybody keeps telling me where to go [This message was edited by Kerry on April 21, 2003 at 05:56 PM.]
  24. Johnnyvegas You sound like your trying to say the dynamics of the system don't affect Goecaching and all Geocachers simply have to be oblivious to these dynamics. Maybe there wouldn't be as many queries similar to this if there was more understanding of these dynamics even if these dynamics might not play a major role in some applications all the time (such as caching) they certainly will play a role at some time, that's almost guaranteed. It's really an absurd statement saying "Time of day, no problem" as put simply it does and if you'd like to put forward some facts that dispute that "Time of Day" is no problem then please feel free. Cheers, Kerry. I never get lost everybody keeps telling me where to go
  25. quote:Originally posted by Johnnyvegas:It real simple. I have used my GPSR at all times of the day and night with way points I have saved in it or load from map programs I have and use, and I have never had a problem with accuracy. Of course I am only speaking from experiance in the field. Let face it, what happens in the feild under real conditions is what really counts. Well it ain't that simple and obviously you don't use GPS for any thing that critical as if you did then you'd understand more about the possible problems and issues. The next time you fly at least hope the pilot understands why they do pre flight checks for possible outages and what RAIM predictions are all about. In certain areas NOT knowing what is probably going to happen "in the field" (in advance) comes down to incompetence. Cheers, Kerry. I never get lost everybody keeps telling me where to go
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