الاحداثياث الجغرافية

[صالح عريبي]

[السلام عليكم
مالفرق مبين Geographic coordinate system and Proejction coordinate system [/size]وشكرا

[رسلان احمد عثمان]

السلام عليكم حسب علمي
Geographic coordinate system
هو نظام يتعامل بالاحداثي الجغرافي
Proejction coordinate system
نظام يتعامل بالصيغة المترية
والله اعلى واعلم

[نجد جمال]

[align=left]A projected coordinate system is defined on a flat, two-dimensional surface.[/align]

Map projection classifications[align=left]
Map projections can be generally classified according to what spatial attribute they preserve.


Equal area projections preserve area. Many thematic maps use an equal area projection. Maps of the United States commonly use the Albers Equal Area Conic projection.

Conformal projections preserve shape and are useful for navigational charts and weather maps. Shape is preserved for small areas, but the shape of a large area, such as a continent, will be significantly distorted. The Lambert Conformal Conic and Mercator projections are common conformal projections.

Equidistant projections preserve distances, but no projection can preserve distances from all points to all other points. Instead, distance can be held true from one point (or a few points) to all other points or along all meridians or parallels. If you will be using your map to find features that are within a certain distance of other features, you should use an equidistant map projection.

Azimuthal projections preserve direction from one point to all other points. This quality can be combined with equal area, conformal, and equidistant projections, as in the Lambert Equal Area Azimuthal and the Azimuthal Equidistant projections.

Other projections minimize overall distortion but don't preserve any of the four spatial properties of area, shape, distance, and direction. The Robinson projection, for example, is neither equal area nor conformal but is aesthetically pleasing and useful for general mapping. [/align]







[align=left]A geographic coordinate system (GCS) uses a three-dimensional spherical surface to define dcilocations on the earth. A GCS is often incorrectly called a datum, but a datum is only one part of a GCS. A GCS includes an angular unit of measure, a prime meridian, and a datum (based on a spheroid).[/align]

[نجد جمال]

[align=center][flash=http://www3.interscience.wiley.com:8100/legacy/college/strahler/0471238007/animations/ch03_animations/animation2.html]WIDTH=800 HEIGHT=600[/flash][/align]