FieldAgent Web: Accessing Satellite Imagery

Accessing Satellite Imagery

Satellite map layers are now clipped to the field boundary!

This allows for the histogram of NDVI or NDRE values within a field to be shown. This also allows for the map to be displayed in a High Contrast (Equal Area) view.

Accessing Satellite Imagery

Most FieldAgent subscriptions include access to satellite imagery products.  The instructions below detail the process for accessing Sentinel satellite data.  Sentinel is operated by the European Space Agency.  The process for locating and using other imagery sources within FieldAgent is similar to the process below.

Where To Locate Imagery

Log in your FieldAgent account via the web app:

Within your account, select the field of interest and drill into it.
Next, select the layers button next to Map Layer to select imagery.

Deselect the highlighted drone icon and select the satellite icon to highlight in green.  This filters to only show satellite data.  The type of image (NDVI, RGB, and others) and the collection date are displayed.  Some systems provide an estimate of the cloud cover in the imagery, but not all constellations support this filter.

Scroll to find the date you wish to view satellite imagery for.
Tip: Try to find days with very high sunshine percentages. Higher sunshine percentages mean less cloud cover and better data. 
Select all the datasets you wish to view and compare.

Scroll to the top and select the "Back" arrow to return to the field page where your selected map layers will now be listed.

How to Adjust Imagery 

Now you can work with the satellite imagery just like any other data or image layer in FieldAgent.
You can change the stacking "Z" order of the layers by dragging map layers up and down to the top (front), and select the hide/view controls to view and compare different layers.

It's also possible to change colormaps and rendering tools for many product, and manage opacity of layers.  Select a layer to manipulate the coloring used as shown below.

How To Utilize Imagery

Satellite Imagery is useful for monitoring your fields from any location. Use satellite to check-in routinely or as a first response after receiving a FieldAgent Notifications. Satellite images may be able to detect and diagnose the conditions in your field. If you're still curious about what's happening in your field, you can use satellite images to pinpoint areas for drone or ground scouting. 

Comparing Zones

Quantitative (Number Based) Comparisons

The comparisons we’ve discussed so far have all been qualitative; creating visual comparisons of map layers. These visual comparisons can work well and may help with most decision making, however values allow you to put numbers to areas and compare without bias.

Let's say we are comparing three seed varieties or three farming practices in three different locations within a field. We can start by looking at an NDVI crop health satellite layer and performing a visual comparison. In the example below, we can see that all three sections of the field seem to be performing relatively well. If we had to say, the middle section appears to be performing the “worst”, although still very green.

Each pixel in an NDVI or NDRE health map contains a health value for that location. We’ll get into more on these values in the next section, but for now, understand that the higher the number, the “healthier” the location is.

To view average values for each location in this field:

  1. Add zones to the field by clicking on the + button in the zones section.

  2. Draw the zone using the tools on the right side of the window.
  3. Name the zone, click Finish on the right side of the window to complete your drawing and then click Save.
  4. Repeat this for each zone you’d like to compare
  5. Then add an NDVI or NDRE map layer to your screen.
  6. Click on a layer to view the details of that layer.
  7. Scroll to the bottom of the screen on the left and look for the section labeled Zone Statistics. Here you’ll find the average NDVI or NDRE value for each zone you’ve created as well as an average for the full field boundary. 
  8. Click Download Shapefile under the display mode section.

  9. The downloaded file can now be used in a tool such as SMS to create a prescription.

This is useful when comparing zones within a field as shown in the above example, but can also be useful when comparing two fields. Simply compare the Field Boundary Zone Statistics of a Satellite layer on one field to that of another field.

This tool can also be useful for evaluating drydown progression. Below are 5 dates with their NDVI map layers, as well as the Field Boundary NDVI value. You can see the progression from a lush field, to one that is dried down and ready for harvest. By comparing the values across fields, or within zones of a single field, you may be able to direct harvest order.

August 22nd

September 6th

September 16th

September 21st

September 26th

NDVI Value: 0.84

NDVI Value: 0.74

NDVI Value: 0.34

NDVI Value: 0.29

NDVI Value: 0.19

Exporting your satellite zone maps 

to learn more about exporting your zone maps click HERE

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