This article introduces satellite data in PIX4Dfields and explains how to work with it.

Introduction to Satellite data

PIX4Dfields 2.0 allows access to satellite imagery from the Sentinel-2 mission of the European Space Agency (ESA). This gives an excellent mapping opportunity to combine both satellite and drone technologies in agriculture and related industries. Satellite images have been broadly adapted by farmers, researchers, and companies to gather information about their businesses.

Main advantages of satellites are the broad-area coverage, historical data access, and gathering data without the need to be on the field.

Main disadvantages are the obstruction of the images by clouds, the low revisit time depending on location, and the high Ground Sampling Distance (GSD) of the images. However, the resolution is sufficient for many agricultural cases.

Data characteristics:

• Historical data is available globally from 2017.
• Revisit time is ~5 days. For more information: Revisit and coverage.
• All bands are upsampled to a resolution of 5m and stacked in a raster (.tiff).
• Radiometric and atmospheric corrections are applied to deliver bottom of the atmosphere (BOA) reflectance data, processed from L1C data with Sen2Cor.
• The maximum field boundary size for an individual request is ~10000 ha).

How to import Sentinel-2 images in PIX4Dfields

Sentinel-2 images can either be imported into a new project or an existing one.
In order to import images into an existing project, click Import on the layers menu.

Import images icon on Layers menu.

In order to import images into a new project, click  New Project on the dashboard.

After the Import files menu appears;

• Select Download under the Satellite data section.

Import files menu.

• First, the boundary needs to be selected, or it can be created by clicking  Create new or imported by clicking Import shape. Holes in shapes will be discarded, data will be shown for the whole field. If you need the holes in your layer, you can trim it afterwards using the same boundary you used for the satellite download. For more information: Trim layers.
• Once the boundary is selected, the prior month's available images will appear in the graphic.

Satellite image selection menu.

• The X-axis contains the date of each image.
  
• The Y-axis contains the Cloud coverage bars and the average NDVI.
• Click on the bars to display the image on the map.
• The 14 days buttons on the sides allow searching images in those periods.
• Clicking the calendar icon, another month/year could be selected.
• To download an image, select it by clicking on the square above each bar.
• After, the selected days appear on the right-hand side of the menu under Selected days.
• Click Create layers to make them available in the layers menu of PIX4Dfields.
  

Layers and bands available after importing

Two layers are created for each downloaded image, an RGB composite orthomosaic that contains all the available bands, and a precalculated NDVI. Names are created by adding Date + Boundary name.

Bands available for generating indices.

What can I do with the available layers?

All the available features in PIX4Dfields can be used with both layers obtained. The RGB composite orthomosaic can be used for creating indices as it contains all the available bands. Zonations and prescriptions can be created with the NDVI orthomosaic. 

Satellite troubleshooting

• There is a fair-use quota for satellite data in place, it is reset every month.

Quota limit reached error message.

• If access to satellite images is not possible, firewall exceptions must be added.
• In case of problems, you can contact support.

Try PIX4Dfields now

Register for a free 15 days trial to import Sentinel-2 satellite images in PIX4Dfields.