web mapping - Maps zoomed around specific locations (magnifying glass effect)

How do I create a static map where the scale varies based on location?

Example: to drive from a specific location X in Albuquerque to a specific location Y in Chicago, I want to "zoom" around X and Y as follows:

• Near X and Y, the scale is fairly large, so you can see minor streets, buildings, etc, near X and Y.


• Far away from both X and Y, the scale is fairly small, so you might just see long lengths of highway, but no details.

In other words, it's like a regular map with a "magnifying glass effect" around X and Y. The effect should "fade off" smoothly, so there isn't a break in the map.

Reasoning: when traveling between remote cities, the highway travel is often easy (in the sense it doesn't require details), but getting from X to the highway and from the highway to Y can require detailed instructions, knowing minor streets, etc.

EDIT: I've attached a horrible example of what I want to do. Notes:

• This only zooms in on one city, not two.


• This is just plain old image zoom. What I would want is more detail in the Albuquerque area.



• Notice, however, that the roads/highways are continuous: the magnifying does not have a "cutoff" problem.

Answer

This document presents an algorithm to do that:

Harrie, L., Sarjakoski, T., Lehto, L. A variable-scale map for small-display cartography. In: Joint International Symposium on GeoSpatial Theory, Processing and Applications (ISPRS/Commission IV, SDH2002). Ottawa, Canada, july 2002

An example:

EDIT: This kind of representation is quite old. See the plan Conrad Morant (1548):