Question
How can I optimise the display of WMS layers within MapThat?
Answer
MapThat can utilise internal and external Web Map Service (WMS) datasets as layers within a MapThat project. WMS layers are essentially images supplied via a URL, so their display can be a lot faster then trying to render complex geometry. In addition, because WMS layers are being supplied via a URL, instead of via a data download, you benefit from accessing real time data. For example, you can access WMS layers such as Flood Risk Zones from the Environment Agency:WMS layers can either be rendered in MapThat as either one image or using multiple image tiles. By using multiple image tiles you can further increase the speed of rendering your layers, as only the image/s for the current map extents is drawn. To display a WMS using Image tiling simply tick the box in the Admin Forms named – Render Using WMS Tiling. This means that when the user ticks to display the WMS layer, the WMS is rendered by opening smaller ‘tiled’ areas within the map.
If however your Web Server is running slowly, WMS layers that utilise individual tiling may have issues with displaying in MapThat. For example, using the individual tile option can mean that as the WMS loads into the map the image appears slowly, tile by tile, which can be frustrating for users. In these circumstances we would firstly recommend looking at the Web Servers capabilities to fix this issue. Alternately by unticking – Render Using WMS Tiling – and loading the WMS as one image, the WMS will load slightly slower but will load for the whole map extents without any obvious tiling issues.