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Understanding WMTS

Koordinates represents data using the Web Map Tile Service standard - otherwise known as WMTS. In this guide, we give some background on why we use tiled map services, and WMTS in particular, over other standards.

What is a tiled map service?

Tiled maps introduce two simple innovations over earlier standards for representing data (see our note on WMS, below).

First, map loading in web browsers and GIS software happens much faster. Instead of sending users a big ‘screenshot’, tiled maps send a bunch of little map images. Viewed together, these images give users the map view they are after. This means that when you pan across the map—going, say, from Dunedin to Port Chalmers—you don’t need to wait for the entire map to reload, as you would under WMS. Instead, a tiled map simply adds new images to the section of the map already loaded. You can see this at work on or Google Maps.

Second, tiled maps dramatically reduce IT infrastructure costs. Tiled maps pre-generate map images at a bunch of different zoom levels, which means you no longer have live servers generating ‘screenshots’ on demand, as you did with earlier standards.

The benefits of WMTS

WMTS is an advanced form of tiled map service. Unlike other tiled map services, WMTS can be published in different map projections, including the standard NZ Transverse Mercator. This makes it a practical solution for the publication of online maps aimed at both professionals and general users.

Why doesn’t Koordinates use WMS?

Some services use and recommend an earlier standard, known as WMS. WMS was developed back in 1999, and works by giving users a ‘screenshot’ of spatial data. This ‘screenshot’ has to be regenerated and reloaded every time a user repositions the map. When we’re talking about big maps with lots of layers, this adds up to a lot of reloading.

Why does this matter? First, the IT infrastructure costs to support a small number of users are very high. This can make it uneconomic to deliver high-value data to large number of users. Given that it can be hard to predict usage, WMS makes it hard for a data publisher to plan for future infrastructure costs.

Second, WMS is slow and difficult to use, and it doesn’t work with consumer mapping sites like Google Maps. If you’re looking to get visualisations of your datasets seen by a lot of users, WMS isn’t the best choice. It will mean that people will find it harder to get and reuse the data; data release will also be much more expensive.