Re: [Talk-GB] tracing lakes with Potlatch
On Tue, 2010-04-06 at 17:26 +0100, Jason Cunningham wrote: The detail for water is excellent and may be the most 'detailed' vector data OS is going to provide. It's far better than the OSM community could achieve with GPSr's and aerial image tracing. Do you know how OS do the water detail? I've often wondered how they manage to get such good detail of really tiny streams in the middle of nowhere, often obscured by trees. Looking at the second link, there are islands in the stream that are marked on the map, but simply not visible on the aerial imagery. I suspect ground imaging radar would highlight water, but surely this has similar tree obscuring issues. cheers, Henry ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] tracing lakes with Potlatch
Henry Gomersall wrote: Sent: 06 April 2010 5:39 PM To: Jason Cunningham Cc: talk-gb@openstreetmap.org Subject: Re: [Talk-GB] tracing lakes with Potlatch On Tue, 2010-04-06 at 17:26 +0100, Jason Cunningham wrote: The detail for water is excellent and may be the most 'detailed' vector data OS is going to provide. It's far better than the OSM community could achieve with GPSr's and aerial image tracing. Do you know how OS do the water detail? I've often wondered how they manage to get such good detail of really tiny streams in the middle of nowhere, often obscured by trees. They do have about 200 years head start ;-) A lot of stuff nowadays is done from aerial imagery, but they can still drop back to traditional surveying methods if required. Cheers Andy Looking at the second link, there are islands in the stream that are marked on the map, but simply not visible on the aerial imagery. I suspect ground imaging radar would highlight water, but surely this has similar tree obscuring issues. cheers, Henry ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.791 / Virus Database: 271.1.1/2793 - Release Date: 04/05/10 19:32:00 ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] tracing lakes with Potlatch
On 06/04/2010 17:51, Andy Robinson (blackadder-lists) wrote: A lot of stuff nowadays is done from aerial imagery, but they can still drop back to traditional surveying methods if required. It was a strange coincidence that I met an OS surveyor, theodolite in hand, doing just that when I was out surveying the (*still* unopened) new Guided Busway near Cambridge, and for the same reason. David ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] tracing lakes with Potlatch
On Tue, Apr 6, 2010 at 1:37 PM, Henry Gomersall h...@cantab.net wrote: I've been keen for a while to improve the lake and tarns outlines in the lake district. It seems the current data is a little coarse and could be improved. Awesome. Having top-notch maps in popular outdoor areas is one of the big drivers of enthusiasm behind OSM. Also, is it worth bothering, as it seems some of the new OS datasets will have decent lakes and rivers. It's always worth bothering to improve OpenStreetMap, so long as you're OK with the knowledge that at some point in the future someone will improve your work even further! I was improving some loch outlines earlier on today, and anyone who looks at them this afternoon onwards will benefit - irrespective of what the OS datasets may or may not contain in the future. Cheers, Andy ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
Re: [Talk-GB] tracing lakes with Potlatch
Date: Tue, 06 Apr 2010 13:37:58 +0100 From: Henry Gomersall h...@cantab.net Subject: [Talk-GB] tracing lakes with Potlatch To: talk-gb@openstreetmap.org Message-ID: 1270557478.9949.39.ca...@whg21-laptop Content-Type: text/plain; charset=UTF-8 Dear All, I've been keen for a while to improve the lake and tarns outlines in the lake district. It seems the current data is a little coarse and could be improved. The (fairly poor) aerial imagery seems plenty good enough to get a decent outline, but Potlatch won't allow zooming beyond a certain level in this region, which makes it difficult. Is this something the Potlach 2 will allow? Also, is it worth bothering, as it seems some of the new OS datasets will have decent lakes and rivers. Cheers, Henry I've been tracing from the OS 1:25k first series which Andy Robinson is uploading as a potlatch layer. (see http://www.openstreetmap.org/?lat=54.5384502410889lon=-2.8754997253418zoom=13and http://www.openstreetmap.org/?lat=54.3379497528076lon=-2.28412628173828zoom=13 ). You can trace at zoom level 17, and the rectification of the maps is pretty good (compare roads on the maplayer with gps traces). The yahoo imagery for rural areas is worse than useless, IMHO, and the NPE is not well rectified - a comment on the standard of the original mapping, not those who rectified the data for OSM use, I hasten to add. There are very few of the maps available in the Lakes at the moment, but I'm hopeful Andy will continue to upload once the furore over OSOpenData has settled a little. As for the comment from another contributor suggesting don't bother tracing - I say go for it, so long as you have local knowledge of the areas concerned - look further afield (Dales, N York moors etc if you know the areas) and get some detail on, but use the best source for tracing available; which at the moment is OS1:25k First Edition. Cheers, Phil. ___ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
