Checking out the ArcGIS Online update: Multilayer Basemaps

Following Monday's update to ArcGIS Online you can try out the features I previewed in last week's post. There is also a good overview of the new features here, along with links to some examples. The new predominance style for smart mapping is illustrated and explained in a Story Map. I've had a play with the example application for the new Compare Scenes application template and it looks useful for a project I'm about to start, but for this post I'm going to focus on the new multilayer basemap option.

Multilayer Basemaps

These sounded interesting and the illustration in the blog looks great. To get a proper sense of how they work and what they might be useful for I decided to make my own, following the instructions added to the help.

Since the multilayer basemap is built as a Web Map you start by choosing an existing basemap (changing it later means starting again). Adding layers and moving them into the basemap lets you build up your composite basemap on top of this. The layers used in the basemap need to be one of the following: Imagery, Map image, Tile, Vector tile, WMS OGC, WMTS OGC or OpenStreetMap (Bing layers can also be used). I used the Environment Agency’s LIDAR WMS service and added this to the Topographic basemap. Making the LIDAR layer semi-transparent gave me a basemap that shows the LIDAR information but also the placenames (in some areas roads and railways show also show) from the Topographic map, illustrated here with the route of the Pennine Way as a map layer:

The Pennine Way (black line) crosses Wensleydale and passes south of Hardraw Force, in the wooded area in the centre. The dry stone walls are visible at this scale and some old quarry workings can be seen in the NE. The Topographic map label for High Shaw is visible (top centre).

The LIDAR only covers parts of England and this showed up another advantage of the multilayer basemap. As well as getting the placenames and major features for context, it also means that I still have a basemap for the areas that lack  LIDAR coverage:

Having added a layer to your multilayer basemap there is also the option to set it as a reference layer. I didn't read the help page carefully enough and was surprised when the LIDAR layer (set as a reference layer) drew on top of the Pennine Way route in my first attempt. So here is the statement from the help page - with added emphasis: Reference layers always draw on top of ALL other layers in the map. The example use for reference layers they give in the help is for labels. The mechanism might also be useful for important business data that shouldn't be obscured in any Web Maps created, such as a layer of constraint polygons.