WebGIS application with OpenLayers 2 - Part 2: Map controls

So far we have created the basic container for a web mapping application GUI. The key aspect in a good application is user experience. This mostly depends on how easily a user can utilize the application, and how smoothly can accomplish a workflow. For a decent user experience, one should think as a user when designing the appearance and mechanics of the application. To make things go right in a WebGIS application powered by OpenLayers 2, the library offers a wide variety of controls. As developers, the responsibility is on us, if we get the most out of it, or not. This is the part where OpenLayers 2 shows its advantages even against its successor. The following post will demonstrate how we can extend our application with minimal programming, and mostly controls offered by OpenLayers 2.

Controls and projections in OpenLayers

OpenLayers has a huge advantage as a Web GIS GUI over Leaflet. It can handle any projection, which can be described by Proj.4. Leaflet supports only two projections (the WGS84 and the Web Mercator). These projections are natively supported in most of the GUIs. As Leaflet is a plugin based, modular library, it has a plugin to use Proj.4 capable projections, but it makes a reverse transformation. It transforms the input coordinates with Proj4js from the defined projection to geographic coordinates. OpenLayers on the other side is capable to handle any coordinate system, so the input maps will be rendered in a projection defined by the developer.