Re: [OSM-talk] Defective GPS trace
On Sun, Jan 3, 2010 at 10:17 AM, Jean-Marc Liotier j...@liotier.org wrote: That would be using a map as an item in a to-do list. It would look ugly to me and I doubt that many people would support that use. Better keep the todo list separate - in another layer if you want it represented geographically. Yes and no. A straight line works almost as well for routing as a correctly surveyed road, and much better than a non-existent way. So rather than a to do list, it's more like a first draft. You might say that in order of priority, we would like the following information about every road: 1) Start and end point 2) Major junctions 3) Name 4) Minor junctions 5) Exact route. 6) Surface 7) Width, lanes, speed limit... The order is debatable though. Steve ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On Sun, Jan 3, 2010 at 9:17 AM, Jean-Marc Liotier j...@liotier.org wrote: Steve Bennett wrote: I'm even tempted to draw a massive straight line between several towns to indicate roads that I know exist but that I haven't surveyed. Would this offend a lot of people here? That would be using a map as an item in a to-do list. IMHO that's ok provided you comprehensively use source:*=* and FIXME=* ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
Liz wrote: On Sat, 2 Jan 2010, Michael Hufer wrote: On the Oregon 550(t) you will find the satellite almanac-screen if you touch the five-bars satellite reception indicator. Thanks, will try it. Later I might read the instructions. I wouldn't bother, they're not much cop :-( ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
Steve Bennett wrote: I've got a trace from today which is significantly out of sync with a path I traced from Nearmap: http://www.openstreetmap.org/edit?lat=-37.880138lon=145.193417zoom=19gpx=594988 http://www.openstreetmap.org/edit?lat=-37.880138lon=145.193417zoom=19gpx=594988 The trace looks like I was wandering through the grassy paddock, but I was actually following exactly that northern most highway=path in the bush. So it looks like the trace is incorrectly recorded something like 50m north of where I actually was. Now, since the discrepancy seems to go away on that track a bit further east (later chronologically), presumably the explanation is the GPS data is faulty. Is this common? I'm new to GPSing, so I'm just surprised. It's a Garmin Oregon 550. Is there anything I can do to reduce, or at least detect, such errors? Steve There are some good points in the previous messages, but I think there's an overall strategy that's: Don't be a slave to your GPS. Be aware of your surroundings - Are you in thick undergrowth? Are you traveling at the bottom of a steep cliff? As has been said, keep an eye on the accuracy reading (except if you're driving of course!) If you are in an area where reception is poor make a note of it, either with a waypoint or, as I do, with old fashion paper pencil. I take photographs to help me remember what my route looked like. I find it extremely useful for recalling road signs street names. If your trace goes straight across a field, but you know you walked around the edge of it, mark it as you walked it, taking a best guess as to where you went. Then tag it with a note or Fixme explaining that it needs updating. Cheers Dave F. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
Craig Wallace wrote: But I'd still agree with Shaun - a single GPS trace is not really accurate enough for adding ways to OSM IMO. Whilst I agree - more the merrier, just because you have only one trace it's not a valid reason not to upload it. If you feel it's an accurate representation, good. If not, add a note or Fixme tagged explaining that it needs retracing to get a more accurate average. IMO, if your policy was followed, OSM would be a fraction of it's size poorer for it. Cheers Dave F. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
2010/1/1 Ulf Möller o...@ulfm.de You can check the satellite screen on the Garmin. It should show an estimated position accuracy. The eTrex often claims 10m accuracy when in fact it is 50m off, so that doesn't really help. Using two different GPS receivers is a good idea if you don't want to survey twice. while this might help in the case your devices calculations/capabilities create the offset, this is still no help in the case of atmospheric interferences. Generally I'd say the more traces you can get, the better is. If you got only 1 trace that shouldn't prevent you from mapping though: enter the data the best you can (detailed tags are at least as valueable as positional accuracy), and probably someone else will optimize the track with new data in the future. Cheers, Martin ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On Sat, Jan 2, 2010 at 3:40 AM, Craig Wallace craig...@fastmail.fm wrote: But I'd still agree with Shaun - a single GPS trace is not really accurate enough for adding ways to OSM IMO. Hmmm...is there consensus on this view? My approach so far has been any information that is approximately correct is better than nothing. The quality of information can be improved over time, and a way whose endpoints are correct but with a fictitious route is far more valuable than a completely missing way. I'm even tempted to draw a massive straight line between several towns to indicate roads that I know exist but that I haven't surveyed. Would this offend a lot of people here? Steve ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
Steve Bennett wrote: On Sat, Jan 2, 2010 at 3:40 AM, Craig Wallace wrote: But I'd still agree with Shaun - a single GPS trace is not really accurate enough for adding ways to OSM IMO. Hmmm...is there consensus on this view? My approach so far has been any information that is approximately correct is better than nothing. The quality of information can be improved over time, and a way whose endpoints are correct but with a fictitious route is far more valuable than a completely missing way. Anyway you put it, the map will only ever be an approximative representation of reality, so approximation is the name of the game and improvement is part of it. But from approximative to fictious, there is a line that I would not cross. I'm even tempted to draw a massive straight line between several towns to indicate roads that I know exist but that I haven't surveyed. Would this offend a lot of people here? That would be using a map as an item in a to-do list. It would look ugly to me and I doubt that many people would support that use. Better keep the todo list separate - in another layer if you want it represented geographically. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
2010/1/3 Steve Bennett stevag...@gmail.com: completely missing way. I'm even tempted to draw a massive straight line between several towns to indicate roads that I know exist but that I haven't surveyed. Would this offend a lot of people here? I've done this, I knew a road ran between 2 towns but wasn't on OSM, so drew a straight line, and when I was able, I surveyed it properly. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
[OSM-talk] Defective GPS trace
I've got a trace from today which is significantly out of sync with a path I traced from Nearmap: http://www.openstreetmap.org/edit?lat=-37.880138lon=145.193417zoom=19gpx=594988 The trace looks like I was wandering through the grassy paddock, but I was actually following exactly that northern most highway=path in the bush. So it looks like the trace is incorrectly recorded something like 50m north of where I actually was. Now, since the discrepancy seems to go away on that track a bit further east (later chronologically), presumably the explanation is the GPS data is faulty. Is this common? I'm new to GPSing, so I'm just surprised. It's a Garmin Oregon 550. Is there anything I can do to reduce, or at least detect, such errors? Steve ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
Steve Bennett wrote: The trace looks like I was wandering through the grassy paddock, but I was actually following exactly that northern most highway=path in the bush. So it looks like the trace is incorrectly recorded something like 50m north of where I actually was. Now, since the discrepancy seems to go away on that track a bit further east (later chronologically), presumably the explanation is the GPS data is faulty. Is this common? I've experienced the same from time to time. Seems to happen sometimes with garmin devices... when you restart it, it's at the correct position again. I'm new to GPSing, so I'm just surprised. It's a Garmin Oregon 550. Is there anything I can do to reduce, or at least detect, such errors? Start your gps at a known position and look at the map. For eample when you're standing near a road and your garmin tells you something different, restart it. best regards ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On 1 Jan 2010, at 13:07, Steve Bennett wrote: I've got a trace from today which is significantly out of sync with a path I traced from Nearmap: http://www.openstreetmap.org/edit?lat=-37.880138lon=145.193417zoom=19gpx=594988 The trace looks like I was wandering through the grassy paddock, but I was actually following exactly that northern most highway=path in the bush. So it looks like the trace is incorrectly recorded something like 50m north of where I actually was. Now, since the discrepancy seems to go away on that track a bit further east (later chronologically), presumably the explanation is the GPS data is faulty. Is this common? I'm new to GPSing, so I'm just surprised. It's a Garmin Oregon 550. Is there anything I can do to reduce, or at least detect, such errors? It is very common for GPSs to give errors for whatever reason. Interference is very common from things like buildings. Newer units are less likely to have an issue. You simply need to go along that track again a few times to get an averaged out reading. Shaun ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On Sat, Jan 2, 2010 at 12:54 AM, Shaun McDonald sh...@shaunmcdonald.me.ukwrote: It is very common for GPSs to give errors for whatever reason. Interference is very common from things like buildings. Newer units are less likely to have an issue. You simply need to go along that track again a few times to get an averaged out reading. Well...ok. But in this case I have the aerial photography, so I can just trace it, once I know more or less where the path goes. I was just curious if there was a way to detect errors at the time - repeating every trace several times just in case would be pretty inefficient. Anyway, I'll try SLXViper's suggestion. Steve ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On 01/01/2010 14:14, Steve Bennett wrote: On Sat, Jan 2, 2010 at 12:54 AM, Shaun McDonald sh...@shaunmcdonald.me.uk mailto:sh...@shaunmcdonald.me.uk wrote: It is very common for GPSs to give errors for whatever reason. Interference is very common from things like buildings. Newer units are less likely to have an issue. You simply need to go along that track again a few times to get an averaged out reading. Well...ok. But in this case I have the aerial photography, so I can just trace it, once I know more or less where the path goes. I was just curious if there was a way to detect errors at the time - repeating every trace several times just in case would be pretty inefficient. You can check the satellite screen on the Garmin. It should show an estimated position accuracy. Also, you can look at which satellites its receiving. If its locked on to a reasonable number of satellites in a decent spread across the sky, you can be fairly confident in its accuracy. You don't have any sort of WAAS like system in you part of the world do you? That would help a bit. But I'd still agree with Shaun - a single GPS trace is not really accurate enough for adding ways to OSM IMO. I'd say get at least 2, preferably 1 in each direction. If they are close to each other you can be confident its probably accurate. If they are much different, its worth getting a few more traces and taking an average. Though yes, this is not really necessary if you have accurate aerial photography that you can trace from. Craig ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
Craig Wallace schrieb: You can check the satellite screen on the Garmin. It should show an estimated position accuracy. The eTrex often claims 10m accuracy when in fact it is 50m off, so that doesn't really help. Using two different GPS receivers is a good idea if you don't want to survey twice. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On 01/01/2010, at 17.40, Craig Wallace wrote: But I'd still agree with Shaun - a single GPS trace is not really accurate enough for adding ways to OSM IMO. I'd say get at least 2, preferably 1 in each direction. If they are close to each other you can be confident its probably accurate. If they are much different, its worth getting a few more traces and taking an average. I agree with this. I've noticed on my Garmin device, that if the satellite reception is lost or very poor, the device assumes it's continuing along a straight line using the most recently determined vector. Coming from a different direction, the device might be able to grab better hold of the the satellite signal and give you a better trace. Cheers, Morten ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On Sat, 2 Jan 2010, Craig Wallace wrote: You can check the satellite screen on the Garmin. It should show an estimated position accuracy. Also, you can look at which satellites its receiving. If its locked on to a reasonable number of satellites in a decent spread across the sky, you can be fairly confident in its accuracy. The Oregon 550 lacks a pictorial representation of the almanac, and only has five bars telling you whether it thinks it has good PDOP or not. Or it might, but as I've had mine 8 days , the same as Steve has, and it is in a menu I haven't found yet ;) ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On Fri, Jan 1, 2010 at 11:40 AM, Craig Wallace craig...@fastmail.fm wrote: On 01/01/2010 14:14, Steve Bennett wrote: Well...ok. But in this case I have the aerial photography, so I can just trace it, once I know more or less where the path goes. Though yes, this is not really necessary if you have accurate aerial photography that you can trace from. Of course, how can you know whether or not you have accurate aerial photos if you're not sure of the accuracy of your GPS readings? Aerials aren't always georectified correctly. The more independent sources you have, the better. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On the Oregon 550(t) you will find the satellite almanac-screen if you touch the five-bars satellite reception indicator. Micha H. On Sat, 2 Jan 2010, Craig Wallace wrote: You can check the satellite screen on the Garmin. It should show an estimated position accuracy. Also, you can look at which satellites its receiving. If its locked on to a reasonable number of satellites in a decent spread across the sky, you can be fairly confident in its accuracy. The Oregon 550 lacks a pictorial representation of the almanac, and only has five bars telling you whether it thinks it has good PDOP or not. Or it might, but as I've had mine 8 days , the same as Steve has, and it is in a menu I haven't found yet ;) ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
You can also use Oregon's Waypoint Averaging function to make more accurate positioning of waypoints. But you need to do this at different times (say on you next hiking trip when you cross the same waypoint) for this to be really effective. With couple of accurate waypoints it is easier to detect track inaccuracies. Igor On Fri, Jan 1, 2010 at 9:18 PM, Michael Hufer michael.hu...@gmx.de wrote: On the Oregon 550(t) you will find the satellite almanac-screen if you touch the five-bars satellite reception indicator. Micha H. On Sat, 2 Jan 2010, Craig Wallace wrote: You can check the satellite screen on the Garmin. It should show an estimated position accuracy. Also, you can look at which satellites its receiving. If its locked on to a reasonable number of satellites in a decent spread across the sky, you can be fairly confident in its accuracy. The Oregon 550 lacks a pictorial representation of the almanac, and only has five bars telling you whether it thinks it has good PDOP or not. Or it might, but as I've had mine 8 days , the same as Steve has, and it is in a menu I haven't found yet ;) ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
The accuracy shown on your GPS unit is not necessary the actual accuracy, but just a calculated accuracy depending on the signals your unit is receiving. You can experience athmospheric disturbance, plasma-effects, signals reflected off tall buildings, canyon or urban canyon effects, bed satellite constillations etc. If you have SBAS (WAAS/EGNOS) activated you might see an improvement in the signal, but mind that if you are outside the official coverage of such systems you might experience that these corrections are in fact increasing the error. If you have access to other forms of augmentation, such as IALA, make sure that you receive signals from the closest station. Even if you have access to good arial photography, remember that it might be out of alignment, it can be a good advise to gather some good fixes to check the alignment of your photos, this can be several GPS tracks along your trail. The problem of GPS devices drifting off is minimal, though more common in small and cheap devices, in many cases simple augmentation can counter for this, but the built in memory of your unit might also help in adjusting (for better or worse). On Fri, Jan 1, 2010 at 8:39 PM, Igor Brejc igor.br...@gmail.com wrote: You can also use Oregon's Waypoint Averaging function to make more accurate positioning of waypoints. But you need to do this at different times (say on you next hiking trip when you cross the same waypoint) for this to be really effective. With couple of accurate waypoints it is easier to detect track inaccuracies. Igor On Fri, Jan 1, 2010 at 9:18 PM, Michael Hufer michael.hu...@gmx.dewrote: On the Oregon 550(t) you will find the satellite almanac-screen if you touch the five-bars satellite reception indicator. Micha H. On Sat, 2 Jan 2010, Craig Wallace wrote: You can check the satellite screen on the Garmin. It should show an estimated position accuracy. Also, you can look at which satellites its receiving. If its locked on to a reasonable number of satellites in a decent spread across the sky, you can be fairly confident in its accuracy. The Oregon 550 lacks a pictorial representation of the almanac, and only has five bars telling you whether it thinks it has good PDOP or not. Or it might, but as I've had mine 8 days , the same as Steve has, and it is in a menu I haven't found yet ;) ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On Sat, Jan 2, 2010 at 8:17 AM, Aun Johnsen li...@gimnechiske.org wrote: The accuracy shown on your GPS unit is not necessary the actual accuracy, but just a calculated accuracy depending on the signals your unit is receiving. You can experience athmospheric disturbance, plasma-effects, signals reflected off tall buildings, canyon or urban canyon effects, bed satellite constillations etc. If you have SBAS (WAAS/EGNOS) activated you might see an improvement in the signal, but mind that if you are outside the official coverage of such systems you might experience that these corrections are in fact increasing the error. If you have access to When I looked up WAAS on wikipedia a while ago, it appeared that we do have an equivalent system in Australia (although the term WAAS is american), but I'm not sure how to tell whether it's functioning in a given area. I switched the WAAS capability on the GPS on, but again, I don't know if it's actually doing anything. Steve ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
2010/1/2 Steve Bennett stevag...@gmail.com: When I looked up WAAS on wikipedia a while ago, it appeared that we do have an equivalent system in Australia (although the term WAAS is american), but I'm not sure how to tell whether it's functioning in a given area. I switched the WAAS capability on the GPS on, but again, I don't know if it's actually doing anything. There is no GPS augmentation system in Australia, the closest one is in Japan. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
2010/1/2 Aun Johnsen li...@gimnechiske.org: Even if you have access to good arial photography, remember that it might be out of alignment, it can be a good advise to gather some good fixes to check the alignment of your photos, this can be several GPS tracks along your trail. I'm pretty sure the imagery he's refering to is nearmap.com, which I'm not sure how they manage it exactly but they seem to be about sub-metre accuracy... ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
2010/1/2 Steve Bennett stevag...@gmail.com: When I looked up WAAS on wikipedia a while ago, it appeared that we do have an equivalent system in Australia (although the term WAAS is american), but I'm not sure how to tell whether it's functioning in a given area. I switched the WAAS capability on the GPS on, but again, I don't know if it's actually doing anything. There is no GPS augmentation system in Australia, the closest one is in Japan. we will have to disagree on this one. skim to the fifth page of this pdf to find the first listed AU stations http://www.beaconworld.org.uk/files/worldDGPSfreqorder.pdf These of course are the free (unencrypted ones). Encrypted broadcasts are used by surveying firms, and won't be listed. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On Fri, Jan 1, 2010 at 11:49 PM, John Smith deltafoxtrot...@gmail.comwrote: 2010/1/2 Aun Johnsen li...@gimnechiske.org: Even if you have access to good arial photography, remember that it might be out of alignment, it can be a good advise to gather some good fixes to check the alignment of your photos, this can be several GPS tracks along your trail. I'm pretty sure the imagery he's refering to is nearmap.com, which I'm not sure how they manage it exactly but they seem to be about sub-metre accuracy... Than they have done a hell of a job on aligning the fotos, cudos to them. I know that Yahoo imagery varies from less then 1 meter to at least 30 meters on the hi-res, havn't seen nearmap, and as I understand its only for Australia, so I would not have any data to compare with. As far as I know IALA have coverage also in Australia, and I am sure that you can get HF also, though it might inicate stations far away (IALA have a range of about 150km, HF roughly 1000km), these two systems are focused on shipping, so I would guess augmentation stations and transmitters are located along the coast. So saying that Australia have no augmentation systems are plain wrong. Now the question is rather if your handheld device supports IALA. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On Fri, Jan 1, 2010 at 6:49 PM, John Smith deltafoxtrot...@gmail.comwrote: 2010/1/2 Aun Johnsen li...@gimnechiske.org: Even if you have access to good arial photography, remember that it might be out of alignment, it can be a good advise to gather some good fixes to check the alignment of your photos, this can be several GPS tracks along your trail. I'm pretty sure the imagery he's refering to is nearmap.com, which I'm not sure how they manage it exactly but they seem to be about sub-metre accuracy... Where are you getting that sub-metre accuracy claim from? This thread ( http://www.mail-archive.com/talk...@openstreetmap.org/msg03414.html), which you contributed to, throws out 3-5 meters, 1-4 meters, and 5 meters or so. This seems like somewhere that the wisdom of crowds actually applies. I think I'd trust the average of a bunch of independent GPS traces to a single orthorectified aerial - especially in an area which isn't extremely flat. But I guess I might be convinced otherwise, if I'm actually shown the sub-metre accuracy claim, which presumably outlines the methods utilized to ensure such accuracy. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
2010/1/2 Anthony o...@inbox.org: Where are you getting that sub-metre accuracy claim from? This thread (http://www.mail-archive.com/talk...@openstreetmap.org/msg03414.html), which you contributed to, throws out 3-5 meters, 1-4 meters, and 5 meters or so. They claim the imagery should be sub-metre, from what I've noticed the differences between different images on different dates are very close to each other. I can't however verify their claim, I don't have anything accurate enough, my claim was a best estimate based on GPS traces... This seems like somewhere that the wisdom of crowds actually applies. I think I'd trust the average of a bunch of independent GPS traces to a single orthorectified aerial - especially in an area which isn't extremely flat. They're planning to re-fly once a month over capital cities and you can access their older images. But I guess I might be convinced otherwise, if I'm actually shown the sub-metre accuracy claim, which presumably outlines the methods utilized to ensure such accuracy. I've cc'd Ben from nearmap on this email, I haven't seen what they do mentioned before. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
2010/1/2 Aun Johnsen li...@gimnechiske.org: Than they have done a hell of a job on aligning the fotos, cudos to them. I know that Yahoo imagery varies from less then 1 meter to at least 30 meters on the hi-res, havn't seen nearmap, and as I understand its only for Australia, so I would not have any data to compare with. Their imagery is a lot better than yahoo, in places yahoo is noted to be out by 20+m, where as nearmap is pretty consistent. They use planes, not sats dunno if it makes things easier or not. As for comparing, you can always use the GPS data uploaded to OSM. As far as I know IALA have coverage also in Australia, and I am sure that you can get HF also, though it might inicate stations far away (IALA have a range of about 150km, HF roughly 1000km), these two systems are focused on shipping, so I would guess augmentation stations and transmitters are located along the coast. So saying that Australia have no augmentation systems are plain wrong. Now the question is rather if your handheld device supports IALA. I didn't think there way, and the only augmentation I've seen is from mobile phone networks... ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
2010/1/2 Anthony o...@inbox.org: This seems like somewhere that the wisdom of crowds actually applies. I think I'd trust the average of a bunch of independent GPS traces to a single orthorectified aerial - especially in an area which isn't extremely flat. But I guess I might be convinced otherwise, if I'm actually shown the sub-metre accuracy claim, which presumably outlines the methods utilized to ensure such accuracy. Average sub-metre error would still allow for a place or two with 50m error especially over a big area such as Australia, and Steve might have visited one of these places. It would be best to just go there again and see if on the second survey the error is siginificantly lower (or there's still error but the the vector is opposite direction). For example based on GPS traces I can say with some confidence that Yahoo is on average 3m off in my city even though there is a couple of places that are badly mangled. Cheers ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
Thanks for the comments, everyone. In all my playing with nearmap, I have little reason to doubt their accuracy. There are a couple of little seams here and there, but nothing more than a couple of metres. Giving the way this trace here meanders all over the place, I'm pretty confident that the nearmap data is a safer bet than the trace - but I'll be paying more attention to accuracy in the future. Btw, can everyone actually see the trace in the URL I referred to ( http://www.openstreetmap.org/edit?lat=-37.880138lon=145.193417zoom=19gpx=594988- then press G)? I'm a bit uncertain about the different privacy settings in Potlatch. Steve ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] Defective GPS trace
On Sat, 2 Jan 2010, Michael Hufer wrote: On the Oregon 550(t) you will find the satellite almanac-screen if you touch the five-bars satellite reception indicator. Thanks, will try it. Later I might read the instructions. ___ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
