Re: [talk-au] Running stats against GPX files ...
On 24/06/2009, at 12:59 PM, John Smith wrote: Also with my previous answer, you can get away with only 14 bytes per point rather than 17, 3 bytes for time, 4 for lat, 4 for lon, 2 for time, 1 for hdop. Although if reset tracks that go over 65,000 seconds back to zero you could get away with only 13 bytes. No idea if this would compress well or not. However 9000 points uncompressed with 13 bytes per point would give you about 115kBytes, the 9000 point gpx file I compressed came out at 35kBytes. I'd say that unless you're *really* concerned about space, I'd just stick with gzip/bzip2-ing the GPX files. If you are that concerned about space, you'd definitely want to use some form of delta encoding, and probably variable-length encoding too. Why spend a whole four bytes storing the latitude? Presumably it's going to be fairly close to the previous point in the track, not 1km away. Same for time, it'll definitely be after the previous timestamp and not by much. If you want to get really fancy, you can start compressing straight- ish sections with something similar to video I an B/P frame, storing it as a fraction of the way between the two key points, and an offset from the line joining them. But you're probably not that keen :) -- James ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Hi all ...
Resent, because I accidently only sent it to David On 21/06/2009, at 4:56 PM, David Dean wrote: Of course, if the number of kilometres is always the same you could easily work out where the location is anyway by looking at the blank hole in all their traces, helpfully centred on their house. It's a matter of who you're trying to stop from finding out where you live, and how close you're willing to have then get from OSM. Are we trying to stop someone who doesn't really care from noticing exactly where you live, or are you trying to stop someone hell-bent on knowing where you live from even knowing which suburb you are in? If it's just to stop people casually seeing where you live, then cutting out a polygon will probably be enough. For the second case, not uploading GPS tracks may not be enough. I would guess that there are plenty of clues as to where you live just in your edit locations and patterns - like someone's early edits are probably going to be streets near where they live. While I'd prefer that you can't tell exactly where I live, I reckon it would be pretty difficult to stop someone from finding out which suburb I live in. -- James ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Hi all ...
On Thu, 25 Jun 2009, James Livingston wrote: While I'd prefer that you can't tell exactly where I live, I reckon it would be pretty difficult to stop someone from finding out which suburb I live in. I have deliberately looked to see from where editors come so when i find that someone who did something in cairns seems to live on the Isle of Wight I'm not concerned about editing it. They came, they saw, they mapped, and I'll edit where it seems to be changed. But if I think I'm encroaching on a local's territory I'll try to contact them to discuss things. So I do look to see who lives where :-) ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Running stats against GPX files ...
--- On Thu, 25/6/09, James Livingston doc...@mac.com wrote: Because I'm a bit bored, I thought about the above. Assume you want an accuracy of 1m and 1s: Most use 6dp (about 10cm) because it fits neatly in an int, but yea 1m or even multiples of 2 or 3m might be good enough since most GPS won't do better than 2 or 3m accuracy. stored in it's fully glory, using say the 13 byte encoding mentioned If you using delta's you only need 12 bytes, since you in theory wouldn't go over 65,535 seconds. Going down this path you would put the full time stamp in the header. * the DOP has changed Why would this matter, DOP usually varies, although it is usually pointless recording over 4 or 5, and if you want to 1dp multiple it by ten, so you only really need +/-60 so plenty of room to move in a single byte. If the first byte is not -128, then it is the change in altitude since the last point. The second byte is the change in latitude the third byte is the change in longitude, and the fourth is the number of seconds since the last point. Most altitude won't change by +/-60m that quick unless you're on a Qantas flight :) Seriously though, vdop isn't any where near as acurate as hdop, so you could do multiples of 10m. There you go, most points now take up 4 bytes :) in which case you can start doing nibbles instead of bytes, and you might be able to get it down to 2 bytes if you really try. But I'm not that bored. Me either, I had to mess about with nibbles and even single bits in the past and it's not fun. While I agree with your sentiments about GPX, I think some variation of JSON would be more efficient from a programming point of view and potentially just as human readable. I made a post to this effect on the GeoJSON list, they have a basic spec nutted out, but it's lacking when it comes to most of the valuable information stored in GPX files like time stamps, elevation and hdop. If you are bored, the full details of my post can be found here: http://lists.geojson.org/pipermail/geojson-geojson.org/2009-June/000488.html ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Hi all ...
--- On Thu, 25/6/09, Liz ed...@billiau.net wrote: But if I think I'm encroaching on a local's territory I'll try to contact them to discuss things. So I do look to see who lives where :-) You only care about what town or suburb some is in, the discussion was on a little more accurate, down to the street or even the house they live or place of work. There can be all sort of reasons people don't care if you know the town/suburb, but on the other hand there is all sorts of reasons people are wary about letting others know more accurately these locations. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Hi all ...
On Thu, 25 Jun 2009, John Smith wrote: You only care about what town or suburb some is in, the discussion was on a little more accurate, down to the street or even the house they live or place of work. There can be all sort of reasons people don't care if you know the town/suburb, but on the other hand there is all sorts of reasons people are wary about letting others know more accurately these locations. Yes, and I've tried to be a bit obscure about my location, but if you know my name, everyone in town knows which is my house. One person well known to me put his marker in the local cemetery. -- BOFH excuse #35: working as designed ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Running stats against GPX files ...
On 25/06/2009, at 8:02 PM, John Smith wrote: --- On Thu, 25/6/09, James Livingston doc...@mac.com wrote: * the DOP has changed Why would this matter, DOP usually varies, although it is usually pointless recording over 4 or 5, and if you want to 1dp multiple it by ten, so you only really need +/-60 so plenty of room to move in a single byte. That was mostly so that you don't ever record the DOP unless it's changed, because it's not really going to do much over the course of a couple of second. There you go, most points now take up 4 bytes :) in which case you can start doing nibbles instead of bytes, and you might be able to get it down to 2 bytes if you really try. Yep, and there are a heap other things you can do too. It all comes down to what you want to use the data for. Are you constantly access it? Occasional access? Archival purposes? Read-only or are you writing too? If you're doing geospatial processing, then fixed size records (like the 13 byte one mentioned) is good, because you can retrieve any node by it's index. If you're archiving the data, what you care about is how small you can get the collection of tracks (not just individual ones). While I agree with your sentiments about GPX, I think some variation of JSON would be more efficient from a programming point of view and potentially just as human readable. I made a post to this effect on the GeoJSON list, they have a basic spec nutted out, but it's lacking when it comes to most of the valuable information stored in GPX files like time stamps, elevation and hdop. I quite like XML, but *way* too many people use it when they really shouldn't be. You need to ask yourself, do I need the eXtensible bit of XML? I think anyone who blindly uses XML without thinking why is a bit daft, but I also think that of people who will never use it under any circumstances, even if it solves their problems. Anyway... -- James ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Hi all ...
On 25/06/2009, at 8:38 PM, Elizabeth Dodd wrote: Yes, and I've tried to be a bit obscure about my location, but if you know my name, everyone in town knows which is my house. One person well known to me put his marker in the local cemetery. Yeah, small country towns are a whole different matter. If you have a crazy stalker, I don't think they really need to extrapolate GPX traces uploaded to OSM to figure out where you live. There's a fair chance it'd be someone who knows where you live anyway :) -- James ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Running stats against GPX files ...
--- On Thu, 25/6/09, Liz ed...@billiau.net wrote: what about Air France? They find the black box yet? ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Running stats against GPX files ...
--- On Thu, 25/6/09, James Livingston doc...@mac.com wrote: It all comes down to what you want to use the data for. Are you constantly access it? Occasional access? Archival purposes? Read-only or are you writing too? At this stage, I personally, only have one purpose, to collect and upload to OSM, how they cope with it and store it and use it is a different matter again. If you're doing geospatial processing, then fixed size records (like the 13 byte one mentioned) is good, because you can retrieve any node by it's index. If you're archiving the data, what you care about is how small you can get the collection of tracks (not just individual ones). By using deltas you can avoid compression and end up with similar sized data files, which has potentially less processing if you want to sequentially access the file, but yea, there is always a trade off, it all depends on the goals. I quite like XML, but *way* too many people use it when they really shouldn't be. You need to ask yourself, do I need the eXtensible bit of XML? I think anyone who blindly uses XML without thinking why is a bit daft, but I also think that of people who will never use it under any circumstances, even if it solves their problems. JSON offers most of the advantages of XML, without a lot of the drawbacks, XML is often referred to as a horse designed by a committee and they ended up with a camel :) ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
[talk-au] General mapping question :)
Ok, I'm stumped how to show this effectively. Basically Google maps are showing a road which no longer or never existed, on one end it goes through a gate to private property, the other end it looks like a car port and the road/track ends. http://maps.google.com.au/maps?f=qsource=s_qhl=ensll=-25.335448,135.745076sspn=55.047272,114.082031ie=UTF8ll=-26.15826,152.645245spn=0.006885,0.013926z=17 Marked as Horswood Rd on gmaps... I've marked the parts of the road that exists presently on OSM from a GPS survey, but I'm not sure how to mark the road explicitly that it isn't a through fare. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Running stats against GPX files ...
On Thu, 2009-06-25 at 05:16 -0700, John Smith wrote: JSON offers most of the advantages of XML, without a lot of the drawbacks, XML is often referred to as a horse designed by a committee and they ended up with a camel :) The way I see it - XML is good for marking up text. JSON is good for describing structured data. If HTML was based on JSON, it would be somewhat ugly, and I think an XMLish like thing suits it well. On the other hand, I think JSON is a good fit for a gps trace (since it is just structured data), and using XML is bleh. The big reason that XML gets used everywhere is because it gets used everywhere :). If a language didn't have a JSON library and an XML library, the XML one would get written first. So even though it is a clumsy language for lots of things, it is at least a clumsy standard language. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Running stats against GPX files ...
--- On Thu, 25/6/09, Andy Owen andy-...@ultra-premium.com wrote: If HTML was based on JSON, it would be somewhat ugly, and I think an XMLish like thing suits it well. Yes, but we're not talking about displaying html, and in fact most people snubbed xhtml and it virtually doesn't get used at all, so it doesn't seem to be a good choice for that either ;) The big reason that XML gets used everywhere is because it gets used everywhere :). If a language didn't have a JSON library and an XML library, the XML one would get written first. So even though it is a clumsy language for lots of things, it is at least a clumsy standard language. I find XML parsing to be one of the most convulted things to do in general, there isn't a single parser that does it as well as JSON parsers do, then again JSON is basically a blob of memory shared between applications instead of a DB interchange language. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Someone needs some help.
I've cleaned this up with the exception of a couple of abbreviations that I don't know how to map back in to their full names (e.g QYS). While I'm there, I'm tempted to replace the current PGS coastline with the borders from ABS - a good idea ?? cheers On Sat, Jun 20, 2009 at 7:37 PM, Ross Scanlon i...@4x4falcon.com wrote: Hi All, Just been using keepright to go over all the stuff I've uploaded and came across this: http://www.openstreetmap.org/?lat=-34.9987lon=117.8835zoom=13layers=B000FTF Now someone has done a admirable job of adding the ways but has not read the wiki about naming. Most of the names are in all upper case and the type of street is abbreviated in just about all cases. Does anyone know of an easy way to change the names to mixed case and or change the ST to Street etc. Mind you if your bored and have run out of your own uploads etc here's something to do. -- Cheers Ross ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au -- Franc ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Someone needs some help.
--- On Thu, 25/6/09, Franc Carter franc.car...@gmail.com wrote: I'm tempted to replace the current PGS coastline with the borders from ABS - a good idea ?? All you have to do is answer this question: Which looks to be the most accurate? Also take into account the fact that yahoo imagery can be misaligned. In general the ABS data looks more accurate, but be aware of the 2000 node limit and at least several ABS boundaries exceed this and while it's possible to split them it's a pain in the butt to do. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Someone needs some help.
On Thu, 25 Jun 2009, Franc Carter wrote: couple of abbreviations that I don't know how to map back in to their full names (e.g QYS). ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Someone needs some help.
On Thu, 25 Jun 2009, Franc Carter wrote: couple of abbreviations that I don't know how to map back in to their full names (e.g QYS). Sorry, got carried away with the send button qys as an abbreviation as a word on the end of street name in a coastal town? Quays a google search found Amity Quays ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] Someone needs some help.
Thanks On Fri, Jun 26, 2009 at 7:04 AM, Liz ed...@billiau.net wrote: On Thu, 25 Jun 2009, Franc Carter wrote: couple of abbreviations that I don't know how to map back in to their full names (e.g QYS). Sorry, got carried away with the send button qys as an abbreviation as a word on the end of street name in a coastal town? Quays a google search found Amity Quays ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au -- Franc ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] General mapping question :)
(To the list this time...) Not sure if this applies, but in many rural areas you'll find that public roads may be through gates marked as private property. For instance, the road I live on passes through private property, has an (open) gate marked as private property, but this road is the only access to a few other properties behind it. I've also run into a few instances quite literally out the back of Bourke... 150Km along the 300Km Wilcannia-Bourke track to see a fence warning it's private property and trespassers will be shot at. It's still the main public road though... That said, none of that helps your tagging quandary... 2009/6/25 John Smith delta_foxt...@yahoo.com Ok, I'm stumped how to show this effectively. Basically Google maps are showing a road which no longer or never existed, on one end it goes through a gate to private property, the other end it looks like a car port and the road/track ends. http://maps.google.com.au/maps?f=qsource=s_qhl=ensll=-25.335448,135.745076sspn=55.047272,114.082031ie=UTF8ll=-26.15826,152.645245spn=0.006885,0.013926z=17 Marked as Horswood Rd on gmaps... I've marked the parts of the road that exists presently on OSM from a GPS survey, but I'm not sure how to mark the road explicitly that it isn't a through fare. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] General mapping question :)
--- On Thu, 25/6/09, Jason Stirk jst...@oobleyboo.com wrote: Not sure if this applies, but in many rural areas you'll find that public roads may be through gates marked as private property. I don't think it does, since I doubt a public road would go through a car port some how :) Also, looking at the sat imagery from google there appears to be some kind of dirt track for some of it, but there is also thick areas of trees and no sign of any kind of road. I though about marking it as a turning circle but there wasn't enough area to turn round and I had to do a 5 point turn. For instance, the road I live on passes through private property, has an (open) gate marked as private property, but this road is the only access to a few other properties behind it. I've also run into a few instances quite literally out the back of Bourke... 150Km along the 300Km Wilcannia-Bourke track to see a fence warning it's private property and trespassers will be shot at. It's still the main public road though... ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] General mapping question :)
I think what you've marked is about all you can do. Obviously the road does not go all the way through and the gates at each end are the restriction. Cheers Ross --- On Thu, 25/6/09, Jason Stirk jst...@oobleyboo.com wrote: Not sure if this applies, but in many rural areas you'll find that public roads may be through gates marked as private property. I don't think it does, since I doubt a public road would go through a car port some how :) Also, looking at the sat imagery from google there appears to be some kind of dirt track for some of it, but there is also thick areas of trees and no sign of any kind of road. I though about marking it as a turning circle but there wasn't enough area to turn round and I had to do a 5 point turn. For instance, the road I live on passes through private property, has an (open) gate marked as private property, but this road is the only access to a few other properties behind it. I've also run into a few instances quite literally out the back of Bourke... 150Km along the 300Km Wilcannia-Bourke track to see a fence warning it's private property and trespassers will be shot at. It's still the main public road though... ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
Re: [talk-au] General mapping question :)
--- On Thu, 25/6/09, Ross Scanlon i...@4x4falcon.com wrote: I think what you've marked is about all you can do. Obviously the road does not go all the way through and the gates at each end are the restriction. Putting a gate to mark the end of the road was the best I could think of doing, maybe I should have added a note about it not really existing. I added a similar barrier=gate at -26.1526, 152.6403, there is actually a gate if you keep going forward, but on gmaps the road is shown to take a 90 degree turn and continue. If you try doing a 90 degree turn and keep going you'll run into a fence. ___ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au
