Plumb Bob

Plumb-Bob is a perspective rectifier for digital photo. It's a great addition to your metric surveying toolkit for a variety of fields, including architectural survey, building renovation, furnishing design, and estate agents. A sufficiently large picture (2 megapixels is enough) where 4 known key points are clearly visible. The real coordinates of the 4 key points. These points have to lay on the same plane to be surveyed and must not to be on the same line (collinear). The more distant the points, the lower the margin of error.