一、什么是Coverage

       Coverage是OGC提出的一种表达地理现象的通用数据模型。Coverage可以理解为时空域与属性域之间的映射函数。

　　A coverage is a feature that associates positions within a bounded space (its spatiotemporal domain) to feature
attribute values (its range). In other words, it is both a feature and a function. Examples include a raster image, a
polygon overlay, or a digital elevation matrix.

　

二、Coverage的构成

　　Coverage主要由两部分构成，时空域（domain）与属性域（range）。domain或可理解为函数的区间，而range可理解为函数的值域。

　　A spatiotemporal domain is a set of geometric objects described in terms of direct positions.
　　The range of a coverage is a set of feature attribute values.
 
三、Coverage的种类
　　Coverage主要有两种类型，离散的（discrete coverage，如土地利用类型图）和连续的（continuous coverage，如市区温度分布图）。
　　A discrete coverage has a spatiotemporal domain that consists of a finite collection of geometric objects and the direct positions contained in those geometric objects.A discrete coverage maps each geometric object to a single record of feature attribute values.
　　A continuous coverage has a spatiotemporal domain that consists of a set of direct positions in a coordinate space.A continuous coverage maps direct positions to value records.