[OSM-newbies] The BIG mapping picture

[Iván Sánchez Ortega]

El Sábado, 2 de Mayo de 2009, Ernst Radema escribió:
> I would like to ask for [...] the BIG picture of the mapping process.

Some people survey with GPSs and convert the data into features.
Some people survey with GPSs and use that as a help to trace features.
Some people record features with GPS waypoints, paper and pen.
Some people record features with GPS tracks and photographs. Others use audio 
instead of photographs.
Some people use aerial photos.
Some people just check for consistency errors.
Some people print an incomplete map on paper and scribble the missing data on 
it, then add the missing bits and pieces.
Some people import data from other sources (with permission).

> * Who decides and how is decided what all these points rare: eg in
> Holland ( where I live ) you often encounter a canal, a street, a bike path
> and a foot path next to each other.

OSM does not have a strict ontology. There is stuff that gets defined by 
general consensus, and there is stuff that is only used by few people.


> * Storage of all this information in a huge database

Yep.

> * Rendering of database information into visible map-images
>   * What are OSMarender ( sounds like OpenStreetMaps ) and
>   * Mapnik rendering ?

Osmarender and Mapnik are different ways of making beautiful images with all 
the data in the database.

> * Tiling: maps are cut into tiles of 0,25 x 0,25 degrees on a
> Tile-server.

Nope. First you need to know what a map projection is. Then, you need to know 
about the infamous EPSG:900913 projection. Then you need to know about 
quadtiles.

Wikipedia is your friend here.

> Is this -more- or less- how mapping Works? Is it completely else? Who has
> more information, corrections, additions?

The whole picture is huge. OSM is not about maps, it's about map *data*. 
The "big picture" changes from day to day because there is people researching 
into new ways to survey, people researching into new ways of editing the 
data, new ways of storing and retrieving the data, new ways of checking for 
errors, new ways of rendering maps, new ways of putting the map data to new 
and unexpected uses.....


-- 
----------------------------------
Iván Sánchez Ortega <ivan at sanchezortega.es>

Given the opacity of the product, how could a Windows admin ever know as much 
about Windows as a UNIX admin does about UNIX?!
                  -- Roger B. A. Klorese on Postfix Mailing List
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