ch空間信息基礎(chǔ)ppt課件(已修改)
2025-05-17 12:04 本頁面
【正文】 靖娟利 土木工程系 第二章 空間數(shù)據(jù)結(jié)構(gòu) 主要內(nèi)容 空間信息基礎(chǔ) 1 空間數(shù)據(jù)的表達 2 空間數(shù)據(jù)模型與數(shù)據(jù)結(jié)構(gòu) 3 矢量數(shù)據(jù)模型 不規(guī)則鑲嵌數(shù)據(jù)模型 柵格數(shù)據(jù)模型 167。 空間信息基礎(chǔ) 空間信息 基礎(chǔ) 地球模型 地理參考 與坐標系 地圖投影 一、地球模型 地球自然表面 水準面 大地水準面 地球橢球體 地球形狀的概括 一、地球模型 地球表面 水準面 大地水準面 鉛垂線 地球橢球體 一、地球模型 — 橢球體 Spheroids and spheres ? The shape and size of a geographic coordinate system39。s surface is defined by a sphere or spheroid. ? Although the earth is best represented by a spheroid, the earth is sometimes treated as a sphere to make mathematical calculations easier. ? The assumption that the earth is a sphere is possible for smallscale maps (smaller than 1:5,000,000). At this scale, the difference between a sphere and a spheroid is not detectable on a map. ? However, to maintain accuracy for largerscale maps (scales of 1:1,000,000 or larger), a spheroid is necessary to represent the shape of the earth. Between those scales, choosing to use a sphere or spheroid will depend on the map39。s purpose and the accuracy of the data. 一、地球模型 — 橢球體 Spheroids and spheres ? A sphere is based on a circle, while a spheroid (or ellipsoid) is based on an ellipse. ? The shape of an ellipse is defined by two ra
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