The Elevation Interact Map is a map in the ArcGIS Online Map Viewer. The main advantage is that you can apply available raster functions to each elevation layer. The map also has many other tools and abilities because it is the the ArcGIS Online Map viewer after all. The disadvantage for some users is that it is GIS-y and can be confusing or overwhelming. If this is you, stick to the Elevation Viewer.
ArcGIS Online is a deep online web GIS. The help here is directly related to the elevation layers. Refer to help on CT ECO or in depth help about ArcGIS online and its many capabilities. You do not need an account to use the map, however you do need an account to save.
The Content panelon the left lists the layers in the map. Turn ON the layers you want to view and turn OFF all others. The layers form a stack (bottom of the list draws on the bottom of the stack) and each can be turned on and off. A check mark means the layer is turned "on" or visible (as long as no other layer higher on the list is turned on and is hiding it from view).
Zoom to the area of interest using the zoom tools or the mouse scroll wheel.
Reorder the layers by either clicking on the three vertical dots on the left and dragging the layer or by using Move Up and Move Down on the More Options menu, accessed through the three horizontal dots.
Transparency makes the layer see-through. It is a sliding scale from 0% (nothing showing through) to 100% (layer is completely transparent and therefore not visible). Slide the bar to change the transparency of that layer.
Go to the raster function page for detailed instructions on applying raster functions in ArcGIS Online.
Clicking on the map is another way to get more information about that feature or location. The information is shown in a pop-up window and is only displayed for layers that are turned on (checked) in the layer list (see Layers above) AND have pop-ups enabled. All elevation layers in the Elevation Interact map have pop-ups enabled by default.
Multiple results occur when a location is clicked where more than one layer both exists and is turned on. It is evident by the top blue banner in the pop-up. The pop-up banner says (1 of 3). This means 3 results were returned at that spot and the first one is visible. To see the next, click on the tiny right arrow in the upper right of the window. In this example, the location was covered by three different elevation datasets.
The pop-ups have been customized to only show the elevation value. There are many options for customizing pop-ups in the map including making more attributes visible. Look for Configure Pop-up on the More Options menu accessible through the 3 blue horizontal dots next to the layer.
The elevation is reported in the pop-up. Note that elevation values are in meters for all datasets EXCEPT the 2016 which is in feet. You may want to consider customizing pop-ups the pop-up so that more than the elevation is visible.
There are a number of ways to add other layers to your ArcGIS Online map. Detailed instructions can be found on the CT ECO on ArcGIS Online help page.