1.3.3. Transforms in Action

Variable Scale Map Example

In this animation below you will be able to experiment with a variable scale transformation applied to a map. In this example we have used the function of (Harrie et al. 2002). This defines two radii. Within the first the map is at a constant magnified scale. Outside of the second the map is at a constant base scale. The transformation then varies the scale smoothly between. Having two radius has the advantage that in the focus region there is no distortion of the map because of the scale, which makes it easier to read.

Instructions for use

• Once the map has loaded, the first thing you will need to do is to click within the map and drag the mouse to define the focus region. You will see the two circles, the inner circle in red shows the region of map that will be magnified. The outer circle in green shows the limit of the transformation, beyond this the map will return to its base scale.
• On the right you will see an interactive graph of the magnification function. Moving the lower horizontal scroll bar will change the size of the green circle. Moving the vertical scroll bar will change the amount of magnification within the inner, red circle.
• To reposition the focus region simply click and drag again within the map.