[OSM-dev] [OSM-talk-nl] conversion AND data

[Stefan de Konink]

On Mon, 30 Jul 2007, Marc Kessels wrote:

> Anyhow: my program actually does this: you can specify a bounding box
> (in the source, could be a command line parameter, but "make 2AND" is
> just as simple for me....) and it will look at ways which have at least
> one point in this bounding box. The program will use much less memory in
> that case, of course.
> In case you make the bounding box as large as the Netherlands (or make
> the bouding box always return "-1") you do need to remember all nodes,
> and it will consume a lot of memory.
> I suppose you are suggesting to divide the complete country into several
> bounding boxes, and export per box. Am I right?

Per segment a bounding box as big as -1 < n < 1 - segment. So not a
linear segmentation, it would suck on the boundaries of it.

Get next segment from AND data
 - Get previous, next segment
  - Calculate boundingbox of 3 segments
   - Fetch boundingbox OSM/Output
    ? empty: merge
    ? nonempty:
       Join segments based on requirements X,Y,Z (name for example)
       Levenstein distance tricks etc.
       Other merge tricks.

> This would require that you go through the AND data a multiple number of
> times, which would take quite long. Also you will have an issue with
> ways that extend through a multiple number of boxes. Of course you could
> write some logic to catch this (e.g. by using only the most top left
> coordinate of a way) and output each way only one time, but you still
> have an issue that you are most likely creating duplicates of nodes
> outside of the current box. (the way will be attached to another way in
> another box, for wich also a new nodeID will be created). This could be
> solved by looking through the already created OSM file, but than you
> again have a file-access, and I think it will then be as slow as
> swapping data from and to memory...

There is nobody saying you should do this in one phase, instead of
specialistic reduce staps. (For example phase 1, check for duplicate...)


> Obviously, I did not need to go through this hassle, since my machine
> did have enough memory.... :)

Sure, I don't want to sound hard because you made this in the first place,
which is a very good job. But I could consider this lazy programming and
bad design. Sure *it* works and it should probably only run one time, but
since people are now experimenting with it, it could have been designed
better reducing the memory requirements. Since this was no objective or
requirement for you we should not bother...



Anyway my comments can always be dropped to the dustbin :)




Stefan