一、什么是Coverage
Coverage是OGC提出的一種表達地理現象的通用數據模型。Coverage可以理解為時空域與屬性域之間的映射函數。
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的構成
Coverage主要由兩部分構成，時空域（domain）與屬性域（range）。domain或可理解為函數的區間，而range可理解為函數的值域。
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的種類
Coverage主要有兩種類型，離散的（discrete coverage，如土地利用類型圖）和連續的（continuous coverage，如市區溫度分布圖）。
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.