Seeing Changes with View and Compare Modes
This article covers the two "modes," or ways of exploring satellite data layers in Lens: View and Compare.
View mode allows you to view imagery or data layers for a single date. Using the high-resolution image below as an example, say that you notice something different about the cluster of buildings from what you've seen in past years:
Compare mode enables you to see how an area of interest has changed from one date to another. You can select two dates on the top bar and drag the slider across the images to see areas where changes might have occurred. You can compare imagery between two different time periods, or even compare different types of layers, such as truecolor landcover, index layers, falsecolor, landcover, and more.
Click the Plus button on the right to add a new image, and select the layer and date in the dropdowns.
And when you notice a change worth documenting, whether it's a new building, timber harvest, or something else, you can make a note to capture your observation. If you’re in Compare mode, the note will include both of the associated images for the two time periods.
Finally, when you generate a report, the imagery for both of those dates will show up in your report, as shown below.
Comparing different layer types
In addition to comparing two truecolor images side-by-side, Compare Mode allows you to select different types of layers. This is useful for recognizing the patterns between truecolor imagery and index layers. By default, Compare Mode will open in the same layer type as the first image you have selected. You can change the layer type and date in the dropdown menus.
In the example below, compare mode is being used to inspect a solar array in both Vegetation Index and truecolor imagery. The white areas show absence of all vegetation, which is confirmed by the highway and solar array clearly see in the truecolor image.
When distinguishing between different features on the ground, it can be helpful to view the vegetation and truecolor versions of the same image, too. In the example below, having the vegetation and truecolor versions of the same image date side-by-side allows us to clearly identify lakes from clouds, and roads from rivers.