Perhaps you're interested in changes in HF in a particular area over time. For instance, you could add an area of interest to your map and then HF datasets from, say, 2010 and 2021 to visualize the change. You can also get summary information for some datasets if you click on the three dots next to your Area of Interest in the main layers panel and then "Summaries", to compare time periods.
Is there any reason to use the HF layers from older years than the most current year? I see you can select different years in this app.
Perhaps you're interested in changes in HF in a particular area over time. For instance, you could add an area of interest to your map and then HF datasets from, say, 2010 and 2021 to visualize the change. You can also get summary information for some datasets if you click on the three dots next to your Area of Interest in the main layers panel and then "Summaries", to compare time periods.