severin.menard at gmail.com
Mon Jul 7 23:09:27 UTC 2014
On Mon, Jul 7, 2014 at 1:09 PM, Alexander W. Janssen <
alexander.janssen at gmail.com> wrote:
> On Mon, Jul 7, 2014 at 10:43 AM, Dan S <danstowell+osm at gmail.com> wrote:
> > Hi Alex,
> Hi Dan!
> > 1) Yes, sometimes it's frustratingly difficult with low-res imagery to
> > know what you can contribute. I would say DEFINITELY carry on mapping
> > those big waterways you mention. In my experience, when we're trying
> > to map an unmapped area, having those landmarks in OSM's database
> > (waterways, major roads, residential areas) really helps future
> > mappers to have points of reference, even if they are approximate and
> > need refining later.
> OK, will continue with that.
> > 2) Re farmlands and forests: I sometimes draw these in, but not often.
> > I agree with you that it seems helpful to give a rough picture of the
> > landscape to expect, BUT on the other hand, I think having these
> > polygons all over can sometimes make the more important jobs harder:
> > jobs such as checking that every single building has been captured.
> > And since these landuse polygons are pretty much never requested in
> > the tasks (apart from landuse=residential which is often a crucial
> > first step), it seems the locals and the aid organisations don't
> > particularly need them. So I would suggest don't spend much time on
> > those.
> Ah, allright. Well, I prioritize anyway; if I'm in the mood I'll just
> draw it anyway :-)
I would say it depends on the situation. Eg in Khartoum (
http://www.openstreetmap.org/#map=12/15.7493/32.5389) I found interesting
to add the residential areas as well as the brownfields and farmlands
around or inside. Brown-fields and farmlands rather than something left
blank also say we did not miss a residential area. In Central African
Republic, basically the residential areas are surrounded by farmlands then
forest. Would be interesting to add the cultivated areas, but maybe through
a remote sensing analysis as the extent will vary from a year to another
and do not need to be extremely precise.
> > If you see tasks which seem fairly complete, it
> > might be a better use of your time to get yourself to a point where
> > you feel confident enough to *validate* other people's completed
> > squares. It takes a little while to feel confident about being a
> > validator but we always need more validation effort than we get.
> Good point; however, when it comes to the validating part, I know how
> hard that is in my area - especially when it comes to correct road
> relations and the such. There are still many grey areas, as soon as we
> run out of unaddressed areas, I'll look other the validation part. So
> that more skilled people can concentrate on that first. Also, Is there
> a feedback process in case I'm doing something wrong? I guess if I
> make a mistake, I'll do the same over and over again. Got the wiki in
> another tab open for reference at all times, but well, you know how it
> > 3) Firstly, you should indeed tag the changeset with the actual
> > imagery you used.
> I thought so.
> > But secondly, if you're not careful about which
> > imagery you use, there's a risk that you might end up tracing from
> > imagery that is a couple of years old or something like that.
> Luckily Bing shows a date in JOSM and all of it shows 2014 up until now.
> > My personal approach would be to try and use the recommended imagery,
> > since someone has usually put effort in to working out which imagery
> > is most appropriate. Also, there's usually a conversation on the
> > mailing list which always gives some clues about what to use.
> I paid attention to this, however other people seem to have the same
> problem - MapBox/Digital Globe is not exactly high-res. In one
> occasion I could use Spot data, but that seems to be rare.
> I wonder if it'd be useful to use Sentinel 1-A data? It's free to use
> and available at ESA's Sentinel Data Hub. However, the 1-A satellite
> was just recently comissioned and the webinterface is a nightmare.
> Also, the data products aren't really curated yet, only level-1
> products are really useful now and we're speaking about TIFF-blobs
> hundreds of Megabytes large. I think these would've to be split to
> tiles and zoom-levels first before they're really useful to JOSM.
> Information about ESA's Sentinel project:
> Sentinel Data hub: https://senthub.esa.int/
> Regristration and usage is free.
> > Dan
> The best thing about procrastinating is you can do it NOW and ANYTIME.
> HOT mailing list
> HOT at openstreetmap.org
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the HOT