矢量切片综述1

简述：

矢量切片服务是下一代ArcGIS for Server的重要功能，此技术来自于Mapbox公司。矢量切片技术的实现将切片服务的高效与矢量地图的灵活结合在一起，是WebGIS的一次革命性的的技术。本着取百家之长的精神，在Mapbox的官网中对矢量切片进行了解，本文正是翻译自Mapbox官网的一篇文章。原文章地址链接：https://www.mapbox.com/developers/vector-tiles/。翻译有不准确还请各位见谅。

正文

Vector tiles are the vector data equivalent of image tiles for web mapping. They apply the strengths of tiling – developed for caching, scaling and serving map imagery rapidly – to vector data. Consider an image tile at the zxy coordinate 14/4823/6160. This image is a PNG that depicts the corner of lower Manhattan with roads, building footprints, and parks:

矢量切片相当于把矢量数据像图片切片那样进行web绘图。他们有切片的优势—成熟的缓存、缩放比例技术，另外对于矢量数据能够快速的提供地图映射。参照图片切片有xyz参数，例如14/4823/6160，这张图片是一个PNG，描绘了曼哈顿下城的角落与道路、建筑足迹以及公园：

A vector tile at 14/4823/6160 would contain all the corresponding geometries and metadata – like road names, area types, building heights – in a compact, parsable format. Vector tiles are a highly performant format that provide greater flexibility in terms of styling, output format, and interactivity.
Vector tiles are designed to use the same tiling and coordinate scheme used by image tiles and take full advantage of HTTP. CDN caching, high scalability and efficient distribution make vector tiles a much more attractive solution than running, say, a enormous cluster of database and application servers that respond to queries on demand.

矢量切片被设计使用与图像切片相同的切割排列方式并且充分利用HTTP，.CDN缓存。这种高扩展性和有效的分配使矢量切片对于庞大的数据库集群和响应查询需求的应用服务器成为更有吸引力的解决方案而不仅是简单运行。

Here are some rough details of our implementation at time of writing:
这里有一些大致的细节在我们实现的时候写的：

• Vector tiles are Protocol Buffers, a compact binary format for transferring messages.
• 矢量切片是协议缓冲（Protocol Buffers），一种紧凑的二进制格式用来传递信息。
• Vector tiles store a serialized version of the internal data that Mapnik uses when rendering maps.
• 当渲染地图时矢量切片使用一系列储存的内部数据进行制图
• Vector tiles are organized into layers (e.g. roads, water, areas), which contain individual features each with a geometry and variable number of attributes per layer(e.g. name, type, etc.).
• 矢量切片被组织到层中（比如道路、水、区域），每一层都有包含几何图形和可变属性的独立要素（例如姓名、类型等等）

附：Mapbox的矢量切片
服务地址：https://api.tiles.mapbox.com/v4
许可：pk.eyJ1IjoibWFwYm94IiwiYSI6IlhHVkZmaW8ifQ.hAMX5hSW-QnTeRCMAy9A8Q
样式：https://www.mapbox.com/mapbox-gl-styles/styles/bright-v4.json

示例：
https://b.tiles.mapbox.com/v4/mapbox.mapbox-terrain-v1/14/4653/6160.vector.pbf?access_token=pk.eyJ1IjoibWFwYm94IiwiYSI6IlhHVkZmaW8ifQ.hAMX5hSW-QnTeRCMAy9A8Q
https://a.tiles.mapbox.com/v4/mapbox.mapbox-streets-v6-dev/14/4956/6060.vector.pbf?access_token=pk.eyJ1IjoibWFwYm94IiwiYSI6IlhHVkZmaW8ifQ.hAMX5hSW-QnTeRCMAy9A8Q