Vector data require far less storage than raster data because arc node lists simplify and reduce the data required to make sense of the features contained in the map.
矢量数据要求的存储要比栅格数据少得多,因为弧节点列表简化并减少了表示地图中包含的特征所需的数据。
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The core of the listing is the defnode macro that takes a node type and a vector of field names, and creates a constructor function for creating maps of that type.