How To Add a Locator Map in ArcGIS Pro
This post details how to add a locator map (or inset map) to a layout in Pro (updated May 2021 for Pro).
Map making is part art, part science, but mainly art, in my humble opinion. It’s often the case that you’ve done the hard yards with analysis and, in the critical map making phase, you want to add some extra maps, like a locator map that shows where your study area is in the context of a larger area, or an inset map that allows you to zoom in smaller areas. In this post I’ll cover how you can do just that.
So let’s say you’ve got some analysis results related to, say, maintenance priorities on some walking tracks in the Oxford area, and are in the process of making your map. You’ve laboured for hours over the colours and labels and all those necessary elements, but what’s missing is a locator map at a smaller scale (larger area) so that people know where the study area is.
Pro projects can contain multiple maps, layouts, tables, etc – this is a nice step up from previous versions where you would have to have a separate project for each layout. If you want to add any additional maps to a layout, you simply need to add a new map. You can do so fromthe Insert tab > Insert New Map.
For 2D maps the right choice is New Map. For 3D scenes, you could choose Local or Global depending on the scale of the new map. We’ll stick with New Map for this post.
This adds a new data frame to your project and inserts a new map window – I’ve called this new map “Locator” (by lazy double-clicking the map name, “layers” by default or changing it in the Properties) and added an unobtrusive basemap to it:
Back on the layout we can now add data into this map for display. To add this new map, use Insert tab > New Map Frame and choose the one to add:
Which I then add to the layout by drawing a box for it:
It’s there but it’s not got the right extent yet. No worries – I can change this by making sure the map frame is selected (it is above) and choosing Activate, , from the Layout tab. I can now zoom in and out, or pan to get it to the right extent:
The extent for the locator is one of those choices that the map maker has to make – I could have gone for the whole extent of Aotearoa, or possibly to the full South Island, or even the extent of the Canterbury Region, but I made the call to focus in on Christchurch, Banks Peninsula and North Canterbury – I’m counting on my reader being able to put this all into a spatial context.
Let’s not forget that the whole point of this post is to add a rectangle to my Main Map that shows where the study area is so the next step is to make a connection between the Locator Map and Main Map frames.
Back on the Insert tab we find an Extent Indicator button:
Since my Locator map is still selected, the option shown under that is for the main map frame. With that picked, the extent of the Main Map is shown on the Locator map:
Nice. I can change the rectangle’s properties (colour, width, etc) by going to the Layout and going to extent rectangle’s properties:
Here I can set up the frame size and colour, add a background and a drop shadow (just because you can doesn’t mean you should…).
Using the same technique, I could also add in an inset map, that shows more detail of my data at a larger scale (smaller area). I’ll add a data frame called Mt Thomas, add in my data (I could just copy and past data from my Data Layers frame to keep the symbology consistent), and set up the extent rectangle in my Data Layers frame (since that’s where it will be displayed). Here’s the result:
We’re getting there but I am by no means finished. I still need to do a lot of thinking about how all my map elements fit together. Am I adding too much to the map? Do the additional maps add value? Are they too big and taking up too much real estate? I’m playing some games with map frame colours to try and help make it clear what each map refers to. Is it too much? These are all part of the everyday burden of the map maker and a key part of the process of making effective maps.
Keep in mind that maps are only needed if you want to add spatial data. If you just wanted to add an image or text of some sort, you could pick one of the Graphics and Text items:
There would still be a lot of work needed to get this particular map up to a more professional level, but it’s a good start. Being able to show extent rectangles like this is an effective way to give your map reader a better sense of where they are and also show more detail.