Template:Cross ratio metrology example.svg
From Vigyanwiki
Use of cross-ratios in projective geometry to measure real-world dimensions of features depicted in a perspective projection. A, B, C, D and V are points on the image, their separation given in pixels; A', B', C' and D' are in the real world, their separation in metres.
- In (1), the width of the side street, W is computed from the known widths of the adjacent shops.
- In (2), the width of only one shop is needed because a vanishing point, V is visible.
