Using the Analyze Area Tool for Ecological Monitoring

Analyze Area allows you to easily visualize seasonal patterns and year-over-year changes in vegetation and surface water. Drill down to specific areas of interest on your property and see how conditions have changed over the last several months or years. We derive these data from Sentinel-2 satellite data, an ensemble of two satellites – the first launched in 2015 and the second in 2017. The 10-meter resolution Sentinel-2 data are ideal for tracking changes over time due to the high weekly data capture frequency. You can explore details on vegetation, water, and snow for targeted areas of interest within a property. Find more information on these metrics in the Map Overlays article.

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Using Analyze Area

The first step is to select the Analyze Area button on the right side of the screen. Clicking on this polygon icon will make the Analyze Area pop-up box appear, and you will be able to draw boundaries around your targeted area of interest by clicking to drop each point and double-clicking to close the polygon.

Once you’ve drawn your polygon, the Analyze Area box will populate to show how conditions have changed over time. You can choose from vegetation, water, or snow and select the period you would like to visualize in the graph. You can also make a note to associate with this particular part of your property for easy reporting or future reference.

Explore the vegetation, water, and snow graphs using presets (e.g., not water, water) or select thresholds to determine what percent of the selected area was within a specific metric range over your period of interest.

Example showing how to select a category to visualize in the Analyze Area graph. In this case, we have chosen “Water” in a coastal property to determine what percentage of the selected area is water over the last year.

Example showing the “Area in Range” option to visualize in the Analyze Area graph. In this case, we have selected thresholds for the water layer to determine how much of the selected area fell within that range for surface water presence over the last year.

You can use the Analyze Area feature in several ways. For example, the vegetation layer could help determine when a timber harvest occurred on a forested property based on a drop-off of vegetation vigor that did not match past seasonal cycles shown in the graph. Additionally, the water layer enables users to visualize ponding, subsidence, or flooding in specific areas throughout the year.

Exploring chart data

Use your mouse wheel or trackpad to zoom in and out on specific months, and pan horizontally by clicking and dragging the chart body. To reset the visible time range, click on the refresh icon to the left of the x-axis.

If the imagery currently selected in the map view corresponds to a visible graph datum, the data point will have a solid red border. Suppose the imagery does not match a graph datum, such as a truecolor map image with a vegetation Analyze Area chart. In that case, an interpolated data point will appear with a light red border and fill.

Click on the chart to update the map view’s imagery to that layer and date. Launch Compare Mode by first selecting one point, then holding down the shift key and selecting a second point on the chart.

Analyze Area for Water Layers

The y-axis is labeled  Dry Land to Water for both the Surface Water and Water & Moisture layers. However, the two layers focus on separate ranges of NDWI to highlight different types of water presence (moisture vs surface water). Since the Water & Moisture layer corresponds to a lower range of NDWI values  (-0.65 to 0 for Sentinel-2), the resulting graph shows higher values for water presence compared to a graph of the Water layer for the same area. You can hover over the chart to see the derived NDWI data. 

Comparing years with the year-over-year chart

The Analyze Area year-over-year chart allows you to compare data from multiple years on the same annualized axis. You can look at the entire calendar year or compare particular months of interest. The year-over-year chart is experimental; learn more in this support article.

Launching Year Over Year 

The “Year Over Year” chart view option is available in the Analyze Area tool's rightmost dropdown menu.

Once the data loads, you’ll see each year of data represented by a separate line on the chart, distinguished by color. Data for all years are turned on by default to show high-level trends. If you prefer to hone in on specific years, you can toggle individual years on and off by clicking each year at the bottom of the chart or selecting “None” and adding each year of interest back to the graph.

Using the year-over-year chart

Use this chart to look at trends between years, find outliers, and identify areas for closer analysis. Hone in on changes within a specific timeframe by selecting individual years and panning to particular months of interest. This functionality is helpful when monitoring growing season health and productivity or recovery after a significant event.

Get a sense of how different years compare by selecting all years and visually identify any outliers for further analysis. If you want to hone in on changes within a specific timeframe, you can select individual years and pan to particular months of interest. 

Best practices

In many situations, lines from multiple years may overlap. Zoom in on the chart and select only the years of interest to make it easier to click on points of interest and compare data across years. 

Exporting Analyze Area values

To export the values from an Analyze Area chart, click on the three dots icon in the upper-right corner, and select the “Export graph CSV” option. You can also select “Export shapefile” to download the polygon used for the Analyze Area analysis.

The CSV includes three columns: date, the index value (NDVI, NDWI, or NDSI), and area. If the “Average Value” option is selected, the acres column will refer to the total analysis polygon area (e.g., the entire property boundary). If the “Area in Range” option is selected, the acres column will refer to the acreage that falls within that range at each given date. 

In the example below, on 3/25/2020, 25.50 acres of the property fell within the defined NDVI value range.

Capturing Analyze Area charts in notes

You can also save the chart showing trends in the data as a Note in Lens. From the Analyze Area tool, simply add a description of what you're seeing below the graph and click "Create" to save this graph as a note. This will ensure that the chart will be included in the reports you generate about this property. You can also zoom in on the graph from the Notes pane or in the Report as needed.

Best practices 

Opening Analyze Area will not change the imagery currently loaded for the property. You can then review the Sentinel 2 time-series data to better understand the image you have been monitoring. 

If you would like the Sentinel 2 ecological layers (i.e. Moisture & Water, Surface Water, Vegetation, Snow) to be associated with your note, click on a point on the Analyze Area chart to load the imagery for that date. To enter compare made, select one point on the chart then hold shift and select a second point. Both images will then save with your note.