The Sentinel 2A satellite is in its second full season of data collection and has been an important contributor to the creation process of making zone maps. With its repeat coverage of only 10 days, Sentinel has been providing a large number of images during the 2016 & 2017 growing seasons throughout the entire US and Canada. So many in fact, that it’s proving difficult to find storage space for them all.
There are many benefits to Sentinel images beyond its 10-day cycle. At 10 meter resolution for the Blue, Red, Green, & Near Infrared bands, it shows much more variation or detail in a field compared to Landsat which is 30 meter resolution (see Figure 1 below). Having the higher resolution assists in refining ditch bottoms and identifying small drowned out areas, as well as removing border effect to name a few of its many strengths.
Figure 1. A June 19, 2017 Sentinel 2 image (left) and a June 23, 2017 Landsat 8 image (right) of a field in Spokane County, Washington, processed as NDVI’s in our ADMS software.
In addition to the Red, Green, Blue, & NIR bands, Sentinel 2 also has 4 Red Edge bands that show the slight differences in the area between the Red band and the Near Infrared band (bands 5, 6, & 7) and a small area near the upper limits of the NIR band (band 8a in Figure 2). These Red Edge bands can be used in Indices to map leaf area and chlorophyll content in vegetation to better evaluate crop health and detect plant stress.
Starting in late July of 2017, Sentinel images that we at GK Technology have processed are now available to all our customers through the online extraction utility featured in our Consultant Package. Our library also consists of images from the 2016 growing season, but aren’t available due to image format issues, which we hope to address in the off-season. To download Sentinel 2 images you can go to either the GloVis Next orEarth Explorer websites and get them for free at your own convenience. You can also find instructions for this process on our website at GK Technology under the Data Links section.
Most importantly, Sentinel 2 images have become a huge asset to the agricultural mapping business and it appears they will stay that way for years to come. In addition to the 2A satellite, the European Space Agency (ESA) has also put into orbit a second Sentinel satellite (2B) that will be placed in a different orbit from the 2A satellite in order to provide repeat coverage every 5 days between the two satellites. So far, it doesn’t appear that any of the 2B images are available online, but there’s evidence that ESA has started processing imagery from the satellite and is working to bringing it online. It also uses a laser beam as the data link between the satellite and the downlink station on earth so the images collected can be downloaded from the satellite in an extremely short amount of time, which will in turn decrease turn-around times for making the imagery available to users. We look forward to where this could take us and the industry as a whole in the near future!
Figure 2: Source USGS
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