Description: Map constraints include projections and contours
Keywords: Engauge Digitizer, browser based documentation, online manual, Map Constraints

## Engauge Digitizer - Map Constraints

### Projections

Currently, only (somewhat common) cylindrical lat/lon coordinates, and (very rare) polar lat/lon coordinates are supported.

Such popular projections as Lambert, Mercator and UTM are not supported, and any attempts to accurately digitize such projections will not succeed.

In the future, a generalized warping algorithm may be added which would support the vast majority of map projections. Besides being extremely flexible, this approach would be easy to learn and work even in cases where details of the original map projection are not known. However, the disadvantages of the generalized warping algorithm would be that lat/lon lines must exist in the map, and accuracy will probably be degraded.

### Open and Closed Contours

Version 1.5 of Engauge Digitizer first offered support for open and closed contours. The Connect As property of a curve can be changed to Contour, and then the points of that curve are connected according to their age, with one exception. Any point created along an existing contour line (which would have two older endpoints) is treated as if the new point was created sometime between the two endpoints, and inserted between them.