Tile Map of past life (reproduced)

From the ancient Babylonian clay map to today's electronic map, from the Columbus Nautical chart to the modern satellite navigation, the history of the map condenses human curiosity and wisdom, and is also mixed with blood and lust. The history of the map is thick enough, because the map is associated with political, military, and economic ups and downs, and the history of the map is good enough because the map is developed to meet the needs and to accompany the development of science and technology.

For a long time, the map was a game for a small number of people. Military home map Command campaign; Navigator uses map to guide the direction; The country uses a map to mark the territory ... Until the popularity of computer technology, map technology began to serve more areas. But always, professional people, in the professional field, do a map-related professional thing. Until the birth of the tile map.

The birth of the tile map

Map data is typically large in volume and requires sufficient bandwidth and data rendering capabilities. Before the advent of tile maps, maps were used in the desktop software of local area networks. The development of the Internet has spawned the need for maps to be used by browsers, and in 1999 there was a WMS (Web map Service) solution. At the end of the browser, there is no concept of the map, but the browser is born to display text and pictures. The WMS is designed to render the map as a picture on the server side and display the map image on the browser side. The map image size depends on the browser window size.

WMS has greatly advanced the process of Internet maps. The problem is that the WMS generates a large picture each time depending on the browser window size, which is challenging and inefficient for back-end rendering and network transmission. Then there is the idea of wms-c (Cached), which improves efficiency by caching map tiles. Google has become the best practitioner of this idea in engineering practice. 2005, Google Maps online, through efficient tile mapping technology, so that users around the world easy to enjoy the benefits of the map.
Google Maps uses the Web Mecator projection and tile grading cutting scheme, also become the current Internet map de facto standard. Then, Google Maps added network services, real-time traffic, street maps and Google Earth, and the booming Internet map began.

The principle of tile map

When using the Internet map, we see a large map image that fills the entire screen. In fact, this big picture is a number of small images of the same size (usually 256*256 pixels) are seamlessly stitched together according to established rules, these small images are tiles. Tiles are organized according to the pyramid structure shown, and each tile can be uniquely marked by level and row number. When panning the map and zooming the map, the browser calculates the required tiles according to the pyramid rules and gets and splices from the tile server.

Since tiles are static pictures that can be pre-generated through caching and CDN technology, tile servers can provide efficient tile reading services. In addition, browsers get and display multiple small images in parallel, much more efficient than getting and displaying a large picture. Showing the map becomes as simple as displaying the image, which is why the Internet map can carry billions of users.

The evolution of tile maps

The image-based tile (grid tile) opens the door to the Internet map, which is rapidly gaining popularity. However, with the gradual deepening of the move and application of the map, raster tiles have encountered at least two problems:

• Image occupies a large bandwidth and storage, not conducive to the application of the map in mobile devices;
• The picture cannot be interacted with.

Constrained by network bandwidth overhead and storage space, raster tile maps appear to be inherently deficient at the beginning of the mobile side. This encourages the use of vector tiles instead of raster tiles on the mobile side. The vector tile uses the same grading cut scheme as the grid tile, but the tile data is in vector form. Vector tiles are small in size and can be highly compressed, occupying more than a few thousand of storage space than grid tiles. On the one hand, reduce network bandwidth consumption, on the other hand make map offline possible.

At present, on the browser side, vector tile is becoming the mainstream technology of Internet map gradually. But this is not to say that grid tiles will exit the historical stage. Internet map Data Update is not frequent, a single tile needs to display the number and type of objects limited, vector tiles can be pre-generated, the cost of local updating is also very small. Vector tiles are not suitable for frequent data updates, large data volumes, and complex rendering methods.

Interoperable Raster Tiles

In the Geohey data visualization service, the user data is rendered as a picture on the server side according to the input configuration parameters. In many scenarios, you need to view the property information for spatial data. Because the raster tiles cannot preserve the spatial characteristics of the data, the points, lines, and polygons in the tiles lose their ability to interact. So how do you display millions of plots of land data, and do you have the ability to interact with plots?
[The mouse moves freely on the map to full screen experience] in this week's update, the Geohey data visualization service adds Utf-grid capabilities to provide interactive capabilities for grid tiles. What is Utf-grid? This column will continue to tell you, sell a Xiaoguanzi first O (∩_∩) o~~

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Note: This article is reproduced in the "Geohey: Map, hello" column (Https://zhuanlan.zhihu.com/geohey), thanks to the original author

Tile Map of past life (reproduced)