最近几年来，地理信息系统无论是在理论上还是应用上都处在一个飞速发展的阶段。 GIS被应用于多个领域的建模和决策支持，如城市管理、区划、环境整治等等，地理信息成为信息时代重要的组成部分之一； “数字地球”概念的提出，更进一步推动了作为其技术支撑的GIS的发展。 与此同时，一些学者致力于相关的理论研究，如空间感知、空间数据误差、空间关系的形式化等等。 这恰好说明了地理信息系统作为应用技术和学科的两个方面，并且这两个方面构成了相互促进的发展过程。
The IOS icon is used for application-related operations.
Different icons in IOS
AppIcon
Application icon for App Store
Small icons for search results and settings
Toolbar and navigation bar icon
Tab bar icon
9.27.1. AppIcon ¶
AppIcon is the icon of the application that appears on the device SpringBoard (all applications on the default screen).
9.27.2. Application icon for App Store ¶
It is a high-resolution application icon for 512 x 512 or 1024 x 1024 (recommended size).
9.27.3. Small icons for search results and settings ¶
Use this small icon in applications that search for lists.
It is also used with related applications where the function is enabled and disabled on the settings screen. For example, enable location services.
9.27.4. Toolbar and navigation bar icon ¶
A list of special standard icons used in toolbars and navigation bars. It includes shares such as icon cameras, writing and so on.
9.27.5. Tab bar icon ¶
A list of special standard icons is used in the tab bar. It includes icons such as bookmarks, contacts, downloads, etc.
Some different iOS devices have different icons of different sizes. You can see more guidelines for icons in Apple files: ios人机交互界面指南 .