Mapping with Drupal

Chapter 2. Web Mapping Basics

Many people making web-based maps do not come from a geographical information system (GIS) or traditional mapmaking background, and can go years without knowing what a map projection is. This chapter will introduce map projections, data storage, and the challenges of making maps online.

If you just want to start working through the tutorials and making maps, feel free to skim over this chapter and come back to it later. That said, even trained geographers often have to pause to remember which is latitude and which is longitude. While it is not necessary to understand these concepts to make maps with Drupal, there will be a time when it is really helpful. Is all the GPS data that you imported showing up a few meters out of place? You’re probably using mismatched projections. Is your map of Washington, DC, showing up in Antarctica? Your latitude and longitude are probably reversed. The first bug reported for the GMap module in Drupal in October 2005 was because the developer got this wrong.

Note

There are many mnemonics to help remember which is which. A common one is “lat is flat”: on a normal map, the lines of latitude run east-west across the map and look horizontal or flat.

Projections and Coordinate Systems

The world is roughly spherical, but computer screens are flat. How we represent the world on a two-dimensional surface and how we locate ourselves and objects on it are difficult problems, and there are many different ways to handle these issues. A ...