In this monthly feature, we span the globe to examine Our Changing Landscape with a time series of medium resolution RapidEye satellite imagery. The RapidEye archive dates back to late 2008 and already contains more than 13 billion square kilometers of data. For our first edition of 2018, we observed changes in fall colors on the Korean Peninsula; and for this February edition of Our Changing Landscape we move back to the United States with a look at the progression of center pivot agriculture in the San Luis Valley, Colorado during 2017.
The RapidEye Constellation
RapidEye is a constellation of five 5-meter medium resolution satellites each offering five spectral bands of information. The RapidEye constellation offers daily revisits to every location on the planet with a huge footprint that is 77-km wide. The data is priced competitively with a starting cost of $1.28 per square kilometer for all five spectral bands – academics do receive discounts. RapidEye adds a fifth band, the red edge, to the ‘traditional’ multispectral set of blue, green, red and near-infrared (NIR). The additional spectral data in the red edge band allows users to extract more useful land ‘information’ than can be from traditional 4-band imagery sources. When RapidEye imagery is ordered as a Level 3A Orthorectified product, images from multiple dates are extremely well registered, making it the ideal data source for Our Changing Landscape.
Center Pivot Agriculture in the San Luis Valley, Colorado
The San Luis Valley is a relatively flat depositional basin that covers a long narrow path from south-central Colorado to north-central New Mexico about 120 miles (193 kilometers) long and 75 miles (120 kilometers) wide. Located some 7,700 feet (2,347 meters) above sea level, the San Luis Valley is a cold high-elevation desert receiving only 7” to 8” of rainfall per year, making it the driest region of Colorado. Despite the lack of precipitation, the valley has significant water resources from snowmelt, the Rio Grande in the south and then groundwater throughout.
Agriculture has a long tradition in the San Luis Valley fed by groundwater irrigation which is recharged by the melt of winter snow from the surrounding mountains. The summer growing season starts around late May in the valley and lasts until September. The season is characterized by warm, sunny days and cool nights, making it ideal for a variety of crops including barley, potatoes, hay and alfalfa where the region represented a significant portion of Colorado’s total 2014 and 2015 agricultural production. In the San Luis Valley, many fields are watered using center pivot sprinklers as it gives farmers some control over irrigation rates. Center pivot agriculture makes a distinct mark on the landscape, making it a prime focus for this Our Changing Landscape; so off to the 5-meter RapidEye archive we head, to see how center-pivot watered fields changed throughout 2017 in the San Luis Valley.
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