Vector tiles

Key takeaways

Vector tiles belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Vector tiles to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Vector tiles from memory before moving on to harder problems.

Reference excerpt

Vector tiles, tiled vectors or vectiles are packets of geographic data, packaged into pre-defined roughly-square shaped "tiles" for transfer over the web. This is an emerging method for delivering styled web maps, combining certain benefits of pre-rendered raster map tiles with vector map data. As with the widely used raster tiled web maps, map data is requested by a client as a set of "tiles" corresponding to square areas of land of a pre-defined size and location. Unlike raster tiled web maps, however, the server returns vector map data, which has been clipped to the boundaries of each tile, instead of a pre-rendered map image. There are several major advantages of this hybrid approach. Compared to an un-tiled vector map, the data transfer is reduced, because only data within the current viewport, and at the current zoom level needs to be transferred. The GIS clipping operations can all be performed in advance, as the tile boundaries are pre-defined. This in turn means that tiled vector data can be packaged up and distributed, without needing any kind of GIS system available to serve data. Compared to a tiled raster map, data transfer is also greatly reduced, as vector data is typically much smaller than a rendered bitmap. Also, styling can be applied later in the process, or even in the browser itself, allowing much greater flexibility in how data is presented. It is also easy to provide interactivity with map features, as their vector representation already exists within the client. Yet another benefit is that less centralised server processing power is required, since rasterisation can be performed directly in the client. This has been described as making "rendering ... a last-mile problem, with fast, high-quality GPU[s] in everyone’s pocket".

History There is a long history of the use of vector tile schemes in GIS. A very early GIS (circa 1966), the Canada Geographic Information System (CGIS), used a vector tile storage scheme that allowed limited resource computers to efficiently access and process vector map data. CGIS used the term "frame" instead of vector tiles. In 1975, the US Wildlife Service initiated a national program to map and digitize all the wetlands in the US. In 1976 they awarded a contract to Autometric to develop a software application that allowed stereo imagery to be digitized using an analytical stereo plotter. Later support for 2d digitization from single photos (aka single photo resection) on a digitizing table was added. The software was called WAMS (Wetlands Analytical Mapping System). The WAMS data store used a tiled vector structure. Each tile was called a “geounit”. A geounit corresponded to one of the USGS quadrangle scales, typically 1:24000. As the data were digitized, they were immediately stored in the tiled data store and topologically structured. Lines crossing geounit boundaries were automatically split. The storage Coordinate Reference System (CRS) was WGS 72 lat/long. WAMS is described in detail in “The wetlands analytical mapping system: WAMS" [Pywell and Niedzwiadek, 1980] Building on the operational experience gained in implementing and using WAMS as well as from the Map Overlay and Statistical System (MOSS), in 1986 Autometric released a UNIX based commercial GIS that implemented an enhanced tiled and indexed storage and access structure: DeltaMap (later GenaMap). The tiled structure capabilities and indexing scheme is described in "DeltaMap: Not just another GIS". Where WAMS implemented a fixed tile system based on latitude/longitude 1:24000 quadrangles, DeltaMap allowed the user to define any size tile in any coordinate reference system (CRS). In this way, sparse data required only a few tiles whereas dense data could use much smaller tiles. R-trees were used as the indexing scheme for the vector tiles. Further, unlike earlier tiling implementations, DeltaMap/GenaMap used the same tiling and indexing scheme for any geospatial data type including 2d and 2.5d vector and feature data, satellite imagery, 3D grids such as DEMs, and annotation. In the late 1980s, Genasys further enhanced GenaMap to allow "Continuous, seamless" processing of the tiled layers. Basically, from the end user perspective, the tiles became invisible. This capability was true regardless of whether the user were editing, visualizing, querying, or analyzing the data.

Standards and approaches As of early 2015, there is no dominant standard for vector tiles. Approaches can differ in their URL format, data serialisation format, packaging of styling information, and support for projections other than Web Mercator.

Protocol buffers (Mapbox) Mapbox has defined an open standard for vector map tiles called "vector-tile-spec" which uses Google protocol buffers for space-efficient data serialisation. Web Mercator is the projection of reference, but vector tiles may be used to represent data with any projection and tile extent scheme. It is also tied to the Mapnik rendering engine, using a "serialized version of the internal data that Mapnik uses". In March 2015, Esri, the dominant geospatial software maker, announced that they would be supporting Mapbox's vector tiles standard in both server and client platforms.

Mapnik Vector Tile This was an early format developed for the Mapnik renderer.

Other formats The approach followed by TileStache is to allow multiple data serialisation formats; as of early 2015, it supports GeoJSON, ArcJSON, GeoBSON, Arc GeoServices BSON, GeoAMF and Arc GeoServices BSON. The requested format is given in the URL (e.g., https://example.com/tiles/mylayer/2/1/3.json)

Support

Services and applications Vector tiles have been used by the Google Maps Android client since December 2010 and on the desktop client since 2013. Vector tiles for rendering OpenStreetMap data were first proposed in March 2013 and are supported by Mapnik, the most widely used renderer of OpenStreetMap data. Mapbox, a commercial provider of custom cartography tools and hosting, has focused its cartography tool, Mapbox Studio, around vector tiles. The popular, and very powerful, Android client for OpenStreetMap data, osmAnd supports vector tiles, which it calls "vector maps".

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Vector tiles

Start with the simplest possible case. Write down what Vector tiles claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Vector tiles before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Vector tiles ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Vector tiles

In research: Vector tiles appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Vector tiles in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Vector tiles is common in secondary-school and first-year university syllabi. It links to neighbouring topics Google Maps, OpenStreetMap, Web mapping, so understanding it makes those chapters shorter.
In everyday life: Look for Vector tiles outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Vector tiles in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Vector tiles means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Vector tiles out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Vector tiles in simple terms?

Vector tiles, tiled vectors or vectiles are packets of geographic data, packaged into pre-defined roughly-square shaped "tiles" for transfer over the web. This is an emerging method for delivering styled web maps, combining certain benefits of pre-rendered raster map tiles with vector map data.

Why does Vector tiles matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Vector tiles?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Vector tiles.