Mapmaking, by digital or manual methods, involves taking complex geographic information and building a visual image with many components. Creating effective maps requires an understanding of how to construct the elements of the map into a coherent whole that executes the communicative purpose of the map. Visual hierarchy and layout are the cartographer’s tools for organizing the map and completing the map construction. The cartographer layers the mapped geography in an image into a visual hierarchy emphasizing some features and de-emphasizing others in vertical ordering of information. Likewise, the cartographer arranges the components of a map image—title, main map, inset map, north arrow, scale, legend, toolbar, etc.—into a layout that guides the reader’s eye around the horizontal plane of the map. The visual hierarchy and layout processes work together to create the structure of the map image.

Web GIS allows the sharing of GIS data, maps, and spatial processing across private and public computer networks. Understanding web GIS requires learning the roles of client and server machines and the standards and protocols around how they communicate to accomplish tasks. Cloud computing models have allowed web-based GIS operations to be scaled out to handle large jobs, while also enabling the marketing of services on a per-transaction basis.

A variety of toolkits allow the development of GIS-related websites and mobile apps. Some web GIS implementations bring together map layers and GIS services from multiple locations. In web environments, performance and security are two concerns that require heightened attention. App users expect speed, achievable through caching, indexing, and other techniques. Security precautions are necessary to ensure sensitive data is only revealed to authorized viewers.

Many organizations have embraced the web as a way to openly share spatial data at a relatively low cost. Also, the web-enabled expansion of spatial data production by nonexperts (sometimes known as “neogeography”) offers a rich field for alternative mappings and critical study of GIS and society.

As internet use has grown, many paper maps have been scanned and published online, and new maps have increasingly been designed for viewing in a web browser or mobile app. Web maps may be static or dynamic, and dynamic maps may either be animated or interactive. Tiled web maps are interactive maps that use tiled images to allow for fast data loading and smooth interaction, while vector web maps support rendering a wide variety of map designs on the client. Web maps follow a client-server architecture, with specialized map servers sometimes used to publish data and maps as geospatial web services. Web maps are composed of data from a database or file on the server, style information rendered on either server or client, and optionally animation or interaction instructions executed on the client. Several graphic web platforms provide user-friendly web mapping solutions, while greater customization is possible through the user of commercial or open source web mapping APIs. When designing web maps, cartographers should consider the map’s purpose on a continuum from exploratory and highly interactive to thematic and less interactive or static, the constraints of desktop and/or mobile web contexts, and accessibility for disabled, elderly, and poorly connected users.