Maps of the Globe: Create Your Own Projections

[humanino]

I'd like to play with creating maps, as plane representations of the globe. I know a lot has been done, and I even considered buying some online, but at least for fun I'd like to compute my own projections, be able to tune them at will. So I would basically need a correspondence coordinate <-> country at some reasonable resolution level, in the form of a database or something more clever.

Would somebody know how I can get this information ? How do they create maps anyway ? Assume you have a plain list of coordinate for points along all borders in the world, is there an efficient way to compute which country a random point belongs to ?

 

[D H]

A long time ago I worked on a joint NASA/NOAA/WMO/UN effort to put weather satellites around the world. We used the CIA World DataBank II to provide geographic features and country boundaries. Our first target installation was the People's Republic of China. They didn't particularly like the CIA's dashed line separating mainland China and Taiwan. We had to figure out how to hack that out of the DataBank. Our next installation was Argentina. They didn't like the CIA's dashed line between Argentina and the [strike]Falkland Islands[/strike] Islas Malvinas. Our third target was Bangladesh. They didn't like some of the boundaries, either. By that time we had become quite adroit at editing the WDB II.

BTW, the CIA WDB II is still available (although horribly out-of-date). For example, http://www.evl.uic.edu/pape/data/WDB/.

 

[mgb_phys]

The most popular free software is probably http://grass.itc.it/ they also have links to free data sets, as do http://www.openstreetmap.org/

 

[MotoH]

Would you be willing to sail the 7 seas with my in a sailing vessel? (it will have cannons for Africa's coastline)

 

[LudusRex]

I can certainly understand your interest in creating your own map projections. It can be a fun and educational exercise to better understand the world around us. To answer your question about how maps are created, it is a complex and multi-step process that involves gathering data, selecting a projection method, and using specialized software to create the final map.

To begin, cartographers (mapmakers) collect data from various sources such as satellite imagery, aerial photography, and ground surveys. This data is then processed and organized into a geographic information system (GIS) which allows for the manipulation and analysis of spatial data.

Next, a projection method is selected based on the purpose and scale of the map. There are many different projection methods, each with its own strengths and weaknesses. Some common projection methods include Mercator, Robinson, and Peters. Each projection method distorts the shape, size, or distance of certain areas on the map in order to accurately represent the curved surface of the Earth on a flat map.

Once a projection method is selected, specialized software is used to create the final map. This software uses algorithms to accurately project the geographic data onto the selected projection. It also allows for customization and tuning of the map, such as changing colors and adding labels.

To answer your question about obtaining the correspondence between coordinates and countries, this information can be found in a GIS database. These databases are often created and maintained by government agencies or private companies and can be purchased or accessed online. Alternatively, you can also manually create a database by gathering data from reliable sources such as government websites or atlases.

In terms of efficiently computing which country a random point belongs to, there are various algorithms and techniques that can be used. One common method is to use a spatial index, which is a data structure that organizes spatial data in a way that allows for efficient querying and retrieval of data. This can help determine which country a point falls within based on its coordinates.

In summary, creating maps involves a multi-step process that includes gathering data, selecting a projection method, and using specialized software to create the final map. GIS databases and spatial indexing can also be used to efficiently determine which country a point belongs to on a map. I hope this information helps you in your pursuit of creating your own map projections.