Search results
Results From The WOW.Com Content Network
Orthographic views project at a right angle to the datum plane. Perspective views project from the surface onto the datum plane from a fixed location. Aerophotogrammetry, orthophoto from drone, Città Alta, Bergamo, Italy. This photo is properly projected on elevation model, yet on a single building scale, a small tilt is noticeable.
Orthographic projection (also orthogonal projection and analemma) [a] is a means of representing three-dimensional objects in two dimensions.Orthographic projection is a form of parallel projection in which all the projection lines are orthogonal to the projection plane, [2] resulting in every plane of the scene appearing in affine transformation on the viewing surface.
Orthographic multiview projection is derived from the principles of descriptive geometry and may produce an image of a specified, imaginary object as viewed from any direction of space. Orthographic projection is distinguished by parallel projectors emanating from all points of the imaged object and which intersect of projection at right angles.
Orthographic projection in cartography has been used since antiquity. Like the stereographic projection and gnomonic projection, orthographic projection is a perspective projection in which the sphere is projected onto a tangent plane or secant plane. The point of perspective for the orthographic projection is at infinite distance.
Images drawn in parallel projection rely upon the technique of axonometry ("to measure along axes"), as described in Pohlke's theorem. In general, the resulting image is oblique (the rays are not perpendicular to the image plane); but in special cases the result is orthographic (the rays are perpendicular to the image plane).
Two parallel projections of a cube. In an orthographic projection (at left), the projection lines are perpendicular to the image plane (pink). In an oblique projection (at right), the projection lines are at a skew angle to the image plane. Every parallel projection has the following properties:
The correction technique is called image rectification and is a large part of photogrammetry. [2] DOQs produced by the USGS cover an area measuring 7.5-minutes longitude by 7.5-minutes latitude (the same area covered by a USGS 1:24,000-scale topographic map, also known as a 7.5-minute quadrangle) or 3.75-minutes by 3.75-minutes.
The black dimensions are the true lengths as found in an orthographic projection. The red dimensions are used when drawing with the isometric drawing method. The same 3D shapes drawn in isometric projection would appear smaller; an isometric projection will show the object's sides foreshortened, by approximately 80%.