Hi! I'm about to write my own renderer. But there are a few things I don't find myself or that aren't clear to me. So I have a couple of questions, some easy, some maybe not. 1. I used on http://www.openstreetmap.org the "Export" link to get a file of "OpenStreetMap-XML"-Data of my area. The area was around 1km x 1km. Where do I find the official definition for this XML? Which tag-names do exist? ?xml - osm, bounds, node, tag, nd (In my following questions I might refer to them as tag-objects.) 2. For example there were these nd ref="[somenumber]" -tags, all contained in some way-objects. So I just assume the number in the ref-attribute should reference some other tag-object in this xml-file. But it's not like that. The numbers are either unique or sometimes happen to be in another nd-object used there as ref also. Is that a bug in the export function? Or a feature? :P 3. For general purposes of course I want to extract those datas related to a selected area myself out of the planet-file. Assuming I use a xml-planet file: Do I have to look for all node-objects (A) with latitude and longitude inside my area, and then in a second run I would have to look for all tags which contain directly or indirectly aforementionened "ref"-attributes that point to those nodeobjects (A)? Do I have to do it a couple of times, in case there are "ref"-attributes pointing to another way-object? 4. Though I would much prefer to work with a planet file in xml-format, I would switch to pbf-format, if it is much faster in the processing *and* if pbf is definitly state of art in the OSM-project. Are the current planet files xml, or already pbf? Or is the pbf idea already outdated again? Assuming I have a planet file in xml and one in pbf, will they both hold the same data, will one hold a subgroup of the other, or may both contain data that isn't in the other? - Or in short: What should be taken as the official planet file? Assume I have to download the pbf file to get the "official" planet data: Which program to use to convert it all into an xml file? 5. About coastline files: Seeing there are coastline files, does that mean that the coastlines are not included as tag-objects in the planet file, or are they only implicitly included, or are the coastline files just some sort of handy service for map-makers? If they are only implicitly included: Is it difficult to generate those coastlines, so that I just should use the coastline files provided here, or is it fairly simply (technically and in CPU-usage) to generate the coastlines myself? 6. Is it advisable to use the data from http://www.naturalearthdata.com? As far as I have read through the wiki-pages, mapnik uses them, and mapnik is used by openstreetmap.org themselves. Do I need or is it advisable to use http://www.mapability.com/info/vmap1_index.html ? Are there any advantages using that? 7. Last but not least: Should I better use the OSM forums (http://forum.openstreetmap.org/index.php - no link on the homepage) or the help-section (https://help.openstreetmap.org - prominent link on the homepage) for questions? |
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Many of the answers I think are on the wiki.
Hi! And thank you for the answer. I will ask the remaining questions again in single threads. Might be better. =) 1. I found that, and now I found the links to the definitions on that page, too. 2. That's how I imagined it should be. The exported file from the openstreetmap.org export function wasn't like that. ): 3. I hope the definitions will enable me to write my own extractor. 4. True. 5. I will read through. 6. Ok. 7. =) I'll give this here a second try. Greetings WS
(23 Oct '12, 17:05)
WhyStand2
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(a slightly tangential answer) What I'd suggest first is have a go at mapping something local to you and adding it to OSM (using either Potlatch in "advanced" mode so that you can see the tags and node numbers, or JOSM). Then have a go with something that renders the data (not necessarily a full rendering database). That way you'll get familiar with the way the data is connected, and answers to questions like "what's an 'nd' in a way definition" will reveal themselves. On the last point, the questions that you're asking might fit here (though better one at a time!) or on the "dev" mailing list, or (with some context in a pastebin that you can refer to) one of the IRC channels. There is a "Development" area of the forum but it's relatively low traffic. |
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What you should definitely do is to ask one question at a time - nobody is going to write an answer that covers all these questions.
I tried, but it took from before you added your comment ;)