[postgis-users] WKB data in files

Mateusz Łoskot mloskot at forest.sggw.waw.pl
Sun Nov 2 13:49:28 PST 2003

On  02.11 2003 Paul Ramsey wrote:
> I think you have hit the nail on the head. WKB is not really designed as 
>  a file format, but as a transport format. Generally you would store 
> shapes on disk as a GeometryCollection of some sort. But as with shape, 
> you would need somewhere to store your attributes (an assocated file, 
> hooray) and probably an index file to speed up access speed (another 
> associated file, hooray).  And by then, you have reinvented the shape file.

In my simple solution, I'd like to use SQLite database to store
attributes and WKB files to store geometry. SQLite is considered
as analogy to dbf files in ESRI Shape.

> Why is the shape file not suitable to you for on disk storage? There are 
> numerous open source readers and writers in all sorts of languages. The 
> shape file format is often abused, but the proliferation of standard 
> read/write libraries has basically plastered over any lingering 
> interoperability problems with the format.

May be you are right. May be I misunderstand some points.
I think that Shape is not suitable to OpenGIS geometry model.
I'm not sure (I need time to have more experience),
if shapes types stored in Shapefile conform to the geometry model
defined by OpenGIS. Could you explain me that from your experience ?

I could store geometry directly in SQLite, but SQLite stores everything
as text, and encoding/decoding from text to binary could decrease
the performance. 
So, the main reasons I'm going to store WKB in files are:
- conformance with OpenGIS spec. / geometry model
- SQLite specifics
- my application has no access to PostGIS ;-(((

I know Shapelib, and in my first implementation I use
Shapelib (as I said in my first post). Shapelib is a great
library but I'd like to choose the solution matching 
OpenGIS specs and rules better.
So, could you suggest any ?

Thanks for your help


Mateusz Łoskot
mloskot at forest.sggw.waw.pl
GNU/Linux (Slackware 9.0)

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