4 地理空间数据来源#
4 Sources of Geospatial Data
在创建地理空间应用程序时，您使用的数据将和您编写的代码一样重要。高质量的地理空间数据，特别是基础地图和影像，将是您应用程序的基石。如果您的地图不好看，那么无论您如何编写其他部分的程序，您的应用程序都会被视为业余作品。
传统上，地理空间数据被视为一种宝贵且稀缺的资源，通常以数千美元的价格进行商业销售，并且有严格的许可限制。幸运的是，随着“民主化”地理空间工具的趋势，地理空间数据现在变得越来越容易免费获取，且使用限制很少或根本没有限制。虽然在某些情况下，您可能需要为数据付费，例如为了确保数据质量，或如果您需要的数据在其他地方无法找到，但现在通常只需从适当的服务器下载所需的数据即可，而且是免费的。
本章概述了一些这些主要的免费地理空间数据来源。这不是一个详尽的清单，而是提供了对 Python 地理空间开发者来说最有用的数据源的信息。
在本章中，我们将讨论：
一些主要的免费矢量格式地理空间数据来源
一些主要的免费栅格格式地理空间数据来源
其他类型免费地理空间数据的来源，重点是城市和其他地名数据库
When creating a geospatial application, the data you use will be just as important as the code you write. High-quality geospatial data, and in particular base maps and imagery, will be the cornerstone of your application. If your maps don’t look good, then your application will be treated as the work of an amateur, no matter how well you write the rest of your program.
Traditionally, geospatial data has been treated as a valuable and scarce resource, being sold commercially for many thousands of dollars and with strict licensing constraints. Fortunately, as with the trend towards “democratizing” geospatial tools, geospatial data is now becoming increasingly available for free and with little or no restriction on its use. There are still situations where you may have to pay for data, for example, to guarantee the quality of the data, or if you need something that isn’t available elsewhere, but it is now usually just a case of downloading the data you need, for free, from a suitable server.
This chapter provides an overview of some of these major sources of freely-available geospatial data. This is not intended to be an exhaustive list, but rather to provide information on the sources which are likely to be most useful to the Python geospatial developer.
In this chapter, we will cover:
Some of the major freely-available sources of vector-format geospatial data
Some of the main freely-available sources of raster geospatial data
Sources of other types of freely-available geospatial data, concentrating on databases of city and other place names