Developable surface
Topic: Map Projections · NCERT: Class 11, Ch 4 "Map Projections"
Meaning
A developable surface is a surface that can be flattened without stretching, tearing or creasing it. A cylinder, a cone and a plane are developable. You can cut open a paper tube or a paper cone and it lies flat without any damage. The graticule is projected onto one of these surfaces. This gives the three main families of projection: cylindrical, conical and zenithal.
Example
Roll a sheet of paper into a tube round a school globe so that it touches the equator, which passes through Indonesia and Kenya. Trace the parallels and meridians onto it, then unroll it. The sheet lies perfectly flat, and you have a cylindrical projection.
Don't confuse with
- Non-developable surface: a sphere, like the globe, cannot be flattened without tearing or stretching. That is why projections are needed in the first place.
Related concepts
- Non-developable surface
- Cylindrical projection
- Conical projection
- Zenithal projection
- Normal projection
- Oblique projection
- Polar projection