I have a PBF file that contains the following information about a country:
Nodes, each with their own longitude, latitude and properties; used to store points in a 2D space.
Ways, each with their properties, they are connected through nodes; used to store roads, boundaries.
While this file is only 80 MB in its compressed form, it's 592 MB when uncompressed and stored in a DB.
Yeah, and that's only for one country, Belgium. Imagine storing France, Germany and Italy alongside.
Let's take a single highway for example, from Antwerp through Brussels to Charleroi. This would consist of a ton of nodes to store all the turns in the highway, but do I need all these turns? I doubt it.
Let me tell you what I want to be able to do:
I want to view the map at different zooming levels; major cities, minor cities and street level at least.
I want to be able to get routing information between two points.
I want to be able to compute the nearest road to my GPS location.
Search for a location, by means of an index in the database.
But most importantly, the database shouldn't be too big as it will be stored on a mobile device.
So, I thought about a combination of two techniques:
Image tiles for viewing purposes, to working around storing/processing all the individual nodes.
Storing the endpoints of roads for routing information, alongside information about the road.
The problem with this is that I can't compute the nearest road to my GPS location with only this information; imagine that a bend in a highway, I can't determine that I'm on the highway with just the two endpoints. I was thinking about storing intermediate nodes between endpoints but that would be very costly to generate, I think. Also, determining the endpoints of roads (that are like a T-split) is most likely not even that easy as I need to figure out whether I need to store the midpoint at the top of that T-split or not.
So, viewing is easy using image tiles; but I can't find an easy way to do routing and GPS location finding, what kind of storage technique should I be looking into? I find it a bit inconvenient that a
80 MB file turns into a database of
592 MB, I want to reduce that size a much as possible...
What can I do to do this as efficiently as possible? In terms of disk and CPU. I'm targeting a WP7...