So, I feel like a bit of a tool. I'm still working on my Java program to download MNDOT traffic data (mentioned in a previous post), but I decided to switch things up a bit. I decided to throw away my old database and to get new data. I decided that this was a good idea because I'm not sure how reproduceable my results are. I figured that I could probably find a better way to import data in the process. The way that I found isn't any better when it comes to procedures since it's more difficult and takes much longer, but it does give me "better data."
osm2pgsql is a lossy conversion utility. It only adds features that have certain tags, as defined in the config file, and it converts nodes and ways to linestrings and polygons. This means that you can't tell which linestring is connected to which, but for rendering a map that's not important (as opposed to routing).
What the crack?! Routing is at the heart of what I do! Wow -- what a catch. So, what next? Well, I turned to osmosis. This tool is ugly and took forever, but it produces a schema that's almost identical to OSMs. The schema itself is worth the wait. osmosis creates a table called nodes that contains the majority of the data in the database. These nodes include tags, ids, versions, time stamps, and the point itself. "What about the lines?" you might ask. Well, there's a ways table. This table contains an id, some tags, and an array of the nodes listed in the line. Hey, that's cool! That sounds like the beginning of a graph, which would be really useful. Then, I found the way_nodes table, which is a graph. It lists the wayId, nodeId, and the sequence of that node within the way. I spent a lot of time coming up with that kind of stuff in my project! This database won't be easy to draw from, but it seems like it'd be perfect for the types of things that I'm doing -- routing and graph operations. So, what happens when I draw it?
QGIS gives me the finger. Yep. My weapon of choice for the last few years won't work for this database. Due to the number of nodes in the planet.osm file (you know -- THE BIG ONE), the database schema uses a BIGINT datatype for the ids. QGIS won't touch your database unless you use int4 datatypes for the ids. There's a ticket open about it, but it's been lingering for quite some time. So, I'm forced to use another desktop based tool. I'm currently trying uDig. I've only been using it for all of 10 minutes, so I can't speak about it yet -- I haven't had enough time to develop an opinion.
Anywho, hopefully this eases my work and leads to some cool stuff.