Map element: web map, legend, layer list and basemap switcher

The main break night map. It's two in the morning after a hard freeze, and reports of water main breaks keep coming in. The operations room has a big screen, and the director asks one question: where are the breaks, and where are our crews? Next to that, supervisors want the check zones around the pump stations, so they know which breaks might affect service there. If the map on that screen is cluttered, has cryptic layer names, or sits on a busy satellite basemap, people squint and guess. A good dashboard map answers the question in two seconds. In this lesson you'll build that map element in ArcGIS Dashboards. You'll add a legend, a layer list and a basemap switcher so every viewer can read it and adjust it without calling you.

What you will learn. Here's the plan for this lesson. First, you'll see where a dashboard map actually gets its layers, symbols and pop-ups, because that decides where you make most of your changes. Second, you'll add a map element to the dashboard you created last lesson and set its main options. Third, you'll learn the three map tools that matter most for viewers: the legend, the layer list and the basemap switcher. For each one you'll learn when to switch it on and when to leave it off. Our running example is a water utility tracking main breaks. The same steps work for service requests, traffic incidents or storm response.

The web map is the source. Let's start with the most important idea. A dashboard map element doesn't hold its own layers. It displays a web map, the saved map item you build in Map Viewer. Think of the web map as a printed poster and the dashboard as the frame on the wall. The frame decides size and position, but to change what's drawn, you reprint the poster. So layer symbols, pop-ups, layer names and the default basemap are all set in the web map. Save your changes there, reload the dashboard, and they appear. A bonus: one well-built web map can power a control-room dashboard and a mobile dashboard at the same time.

Adding the map element. Now open the dashboard you created last lesson. Choose Add element and pick Map. ArcGIS Dashboards shows the web maps you can access. Search for your water main breaks map and select it. The map settings panel opens. Here you'll find the map tools: legend, layer visibility, basemap switcher, search, zoom and a home button. The home button returns to the default extent, which simply means the starting view of the map. You can also choose whether pop-ups, the small info boxes, show when someone clicks a feature. Click Done, and the map appears in the layout grid. Drag its edges so it takes the largest share of the screen, because on most operations dashboards the map is the star.

Worked example: preparing the web map. Here's our worked example, before we touch the dashboard at all. In Map Viewer we have three reported main breaks, drawn as red points so they stand out. Next comes the pump station that feeds this part of the network. Then a one kilometre check zone around the station, a simple circle that shows crews which breaks are close to it. Now zoom closer to check the view. Are the red points easy to see against the basemap? Do pop-ups show the address and the time reported? Are the layer names words a supervisor would say out loud? If yes, save the web map. The dashboard will now inherit all of this for free.

The legend. The first map tool is the legend. It explains what each symbol means, for example red for main breaks and orange for the check zone around the pump station. The dashboard builds it automatically from the web map's symbology, so if a label in the legend reads "Value 1", the fix is in Map Viewer, not in the dashboard. Turn the legend on whenever color or size carries meaning, such as main breaks classed by the number of customers without water. Watch the count, though: a legend with twelve categories is a legend nobody reads. Three to five categories with plain labels like "Under 50 customers" work well on a wall screen.

The layer list. The second tool is the layer list, called layer visibility in the settings. It lets viewers turn layers on and off themselves. That's handy when some layers are context rather than the main story. During a main break response, the break points stay on, but a supervisor might switch on crew locations or valve locations only when planning a shutdown. The order and names in the list come straight from the web map, so arrange them there, with the most important layer on top. So should every layer go in the map just in case? Not really. Each layer adds loading time and clutter in the list. Include what someone will actually use.

The basemap switcher. The third tool is the basemap switcher. The basemap is the background map under your data. Your dashboard opens with the basemap saved in the web map, and the switcher lets viewers pick another one from your organization's basemap gallery, which your administrator controls. For most operations dashboards, a quiet basemap such as light gray canvas or dark gray canvas works best, because your red main break points pop against it. Imagery is great when a crew leader wants to see whether a break sits under a road or a parking lot. A good rule: start with a quiet default and add the switcher only when viewers truly need to change it.

Quick check of layer names. This slide is optional. It's for GIS admins, so if you don't write code, feel free to skip ahead. If you manage many web maps, a small script can catch bad names before viewers see them. Under the hood, a web map is a JSON document, which is just structured text with a list called operational layers. Each entry has a title and a visibility flag. This snippet uses a small inline copy of that list. It prints each title, whether the layer starts on or off, and flags any title with an underscore, a sure sign of a database name that leaked through. The output shows one layer to rename in Map Viewer. With the ArcGIS API for Python, you could run the same loop over every web map in your organization.

Common mistake: a blank map for viewers. Here's the mistake that catches almost everyone once. You share the dashboard with your field supervisors group, it looks perfect on your screen, and the supervisors call to say the map is blank. The reason: you're the owner, so you can see everything, but the web map, or one of the layers inside it, is still private. A dashboard can't lend its viewers permission to see items they can't open. The fix is to share the dashboard, the web map and every layer to the same group or audience. Always test in a private browser window, signed in as a regular viewer, before you announce the link.

Recap. Let's wrap up. First, a dashboard map element displays a web map, so layer symbols, pop-ups, names and the default basemap are all set in Map Viewer. Fix things at the source, then reload. Second, the legend, layer list and basemap switcher are optional tools. Turn on the legend when colors carry meaning, the layer list for optional context layers, and the switcher only when viewers truly need another background. Third, sharing has to match all the way down. The dashboard, its web map and every layer need to reach the same audience, or your viewers get a blank map.

Your exercise. Now it's your turn. Before the next lesson, build a web map in Map Viewer with at least two layers. Use your own data, or a layer from Living Atlas, Esri's free library of ready-made map layers, such as current traffic incidents or power outages. Rename each layer in plain language, pick a quiet basemap, and check that the pop-ups show useful fields. Then add it as a map element to the dashboard from last lesson, with the legend and layer list turned on. Finally, share everything to one group and open the dashboard in a private window. If the map shows up there, you're ready for indicators next time.