[snodnipper]

huge topic.

> I wish I could learn to build my own tiles, vector or PNG. I don't really understand where the data comes from, how is data gathered and assembled.

There are many data providers out there. You might be interested in OpenMapTiles, which is a pipeline from OpenStreetMap (OSM) data. https://github.com/openmaptiles/openmaptiles

Also check out Maputnik http://maputnik.github.io/editor/

If you want to learn about "tiling schemes" then head over to https://www.maptiler.com/google-maps-coordinates-tile-bounds...

> I'm also really curious about the choices involving the zoom level, how do you decide to render things depending on the zoom level, when is data discarded, to have good detail or better performance and lighter tiles. I would really be willing to try build lighter maps so I can have my own mapping software on a desktop machine.

Lots of different considerations - is a human going to look at the map? If so then a cartographer will determine what is going to be shown at a given scale. There are other constraints too, such as limited space to show data and also hidden constraints, such as the maximum amount of data for a region (e.g. ~500kb per tile in the case of mapbox vector tiles)

> The data sizes and hardware requirements involved are generally pretty big. It could be interesting to see how much details one could achieve to make a "portable" map browser when limiting the data size to 2GB, 5GB or 10GB.

Lots of projects out there doing impressive things there. Quadtree tiles get you so far...k-d trees might yield other useful properties. Skobbler have some pretty impressive data compression technology (~12GiB for global coverage, routable and searchable...with some limitations - skobbler.com/apps). Of course the trick is to discard all that you don't need.

> I would really like to ask why, on some mapping software, you can't see names of large enough cities/places/regions that are obviously there. It often makes it difficult to browse maps properly.

If there is limited budget then the effort to create appropriate labels is limited. Data sources can be limited / incomplete...there can be nuances between jurisdictions etc. and of course label prioritisation has been a longstanding problem. What happens when you rotate a map and the text labels collide with one another...which ones do you keep...which do you discard etc. These things are also context dependent...why not include continent names? Or region names? Or province names? What about the difference between physical and political geography? A cartographer can help ensure that the right information is available at the right time...whilst acknowledging that they have to tell little white lies in every map they make.