Web Mapping Illustrated

Chapter 5. Acquiring Map Data

You are probably eager to start on a project and try out all of these great tools. However, before you can jump in, you have some homework to do. The first step in any mapping project is identifying your data needs. Finding the information you require is your next step.

Appraising Your Data Needs

What you need will vary greatly depending on your goal, so you should first determine the goal or final product of your work. Along with this comes the need to assess what kind of map information you want to portray and at what level of detail. The following sections are a guide to thinking through all your requirements before starting a project.

Vector Maps or Raster Maps?

If you want to make a custom map, you need to determine what kind of map data you require. There are two kinds of maps, each requiring different kinds of map data.

A vector map shows features made up of points, lines, or polygon areas, as in Figure 5-1. For instance, this can be a local road map or a global map showing locations of power stations and their respective countries.

An image or raster map is made from data sources such as aerial photography, satellite imagery, or computer-generated images of Earth's surface. Figure 5-2 shows an example of a raster map made from weather satellite data.

One variant of the raster map is the scanned map. When a paper map is scanned, it is converted into a digital raster map and can then be used as a layer on other maps. This is one way to make mapping ...