science

Tiled web map

Tiled web map is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tiled web map rather than just read about it. In short: A tiled web map or tile map (also known as slippy map in OpenStreetMap), is a web map displayed by seamlessly joining dozens of individually requested data files, called "tiles". It is the most popular way to display and navigate maps, replacing other methods such as Web Map Service (WMS) which typically display a single large image, with arrow buttons to navigate to nearby areas.

Key takeaways

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

Reference excerpt

A tiled web map or tile map (also known as slippy map in OpenStreetMap), is a web map displayed by seamlessly joining dozens of individually requested data files, called "tiles". It is the most popular way to display and navigate maps, replacing other methods such as Web Map Service (WMS) which typically display a single large image, with arrow buttons to navigate to nearby areas. Google Maps was one of the first major mapping sites to use this technique. The first tiled web maps used raster tiles, before the emergence of vector tiles. There are several advantages to tiled maps. Each time the user pans, most of the tiles are still relevant, and can be kept displayed, while new tiles are fetched. This greatly improves the user experience, compared to fetching a single map image for the whole viewport. It also allows individual tiles to be pre-computed, a task easy to parallelize. Also, displaying rendered images served from a web server is less computationally demanding than rendering images in the browser, a benefit over technologies such as Web Feature Service (WFS). While many map tiles are in raster format (a bitmap file such as PNG or JPEG), the number of suppliers of vector tiles is growing. Vector tiles are rendered by the client browser, which can thus add a custom style to the map. Vector map tiles may also be rotated separately from any text overlay so that the text remains readable.

Defining a tiled web map

Properties of tiled web maps that require convention or standards include the size of tiles, the numbering of zoom levels, the projection to use, the way individual tiles are numbered or otherwise identified, and the method for requesting them. Most tiled web maps follow certain Google Maps conventions:

Tiles are 256x256 pixels At the outer most zoom level, 0, the entire world can be rendered in a single map tile. Each zoom level doubles in both dimensions, so a single tile is replaced by 4 tiles when zooming in. This means that about 22 zoom levels are sufficient for most practical purposes. The Web Mercator projection is used, with latitude limits of around 85 degrees. The de facto OpenStreetMap standard, known as Slippy Map Tilenames or XYZ, follows these and adds more:

An X and Y numbering scheme PNG images for tiles Images are served through a Web server, with a URL like http://.../Z/X/Y.png, where Z is the zoom level, and X and Y identify the tile. "One file with all tiles" technology is an alternative with good performance, as demonstrated by PMTiles.

Tile numbering schemes There are three main numbering schemes in use:

Google Maps / OpenStreetMap: (0 to 2zoom-1, 0 to 2zoom-1) for the range (−180, +85.0511) - (+180, −85.0511) Tile Map Service: (0 to 2zoom-1, 2zoom-1 to 0) for the range (−180, +85.0511) - (+180, −85.0511). (That is, the same as the previous with the Y value flipped.) QuadTrees, used by Microsoft.

Standards Several standards exist:

Tile Map Service: an early standard supported by OpenLayers. One difference is the y axis is positive northwards in TMS, and southwards in OpenStreetMap. Web Map Tile Service: a more recent Open Geospatial Consortium (OGC) standard. The de facto XYZ standard referred to above. TileJSON: a lightweight JSON description of all the parameters associated with a web map, created by Mapbox. Bing Maps Tile System, using Quadkeys for addressing.

Client libraries To display a tiled map in a browser usually requires the support of a web mapping framework. This framework handles the retrieval of tiles, display, caching, and user navigation. Popular frameworks for tiled maps include Google Maps API, OpenLayers and Leaflet.

References

External links "How do Web Maps Work?". Mapbox. Example of a tiled marine map for boating

Illustrations

Worked examples

Example 1 — a first encounter with Tiled web map

Start with the simplest possible case. Write down what Tiled web map 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 Tiled web map 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 Tiled web map 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 Tiled web map

In research: Tiled web map 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 Tiled web map 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: Tiled web map is common in secondary-school and first-year university syllabi. It links to neighbouring topics Web mapping, so understanding it makes those chapters shorter.
In everyday life: Look for Tiled web map 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.

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How to study Tiled web map in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tiled web map 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 Tiled web map out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tiled web map in simple terms?

Why does Tiled web map 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 Tiled web map?

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 Tiled web map.