DecimalDegree
目录
DecimalDegree和DegreeMinuteSecond一样是表示经纬度(Longitude/Latitude)的一种地图单位(MapUnit)。
公式如下：DecimalDegree = Degree + Minute/60 + Second/3600
注意上面提到是地图单位，但我们常说的是距离单位(DistanceUnits)，比如英里(Miles)。
以下是维基百科的描述
From Wikipedia, the free encyclopedia
(dd) are often used in Geographic Information Systems (GIS), web-mapping applications such as Google Maps, and GPS devices to express latitude and longitude coordinates, rather than expressing geographic coordinates with degrees, minutes, and seconds (dms).
Accuracy
A value in decimal degrees to an accuracy of 4 decimal places is accurate to 10meters at the equator. A value in decimal degrees to 5 decimal places is accurate to 1meter at the equator. Because the earth is a sphere and not flat the accuracy of the longitude part of the coordinates increases the further from the equator you get. The accuracy of the latitude part does not increase.
Example
With DMS, the geographic coordinates of the United States Capitol are “38° 53′ 23″ N, 77° 00′ 32″ W”. In decimal degrees, West and South are considered to be negative numbers and the DMS is converted to degrees using the formula (D + M/60 + S/3600). Thus the decimal degree representation of the U.S. capitol is “38.8898341, -77.0088651”.
转载自：https://blog.csdn.net/felixschrock/article/details/2223930
