In this monthly feature, we span the globe to examine Our Changing Landscape with time series of medium resolution RapidEye satellite imagery. The RapidEye archive dates back to late 2008 and already contains more than 4 billion square kilometers of data. This month, we look changing snow cover high in the Rocky Mountains over Arapaho National Forest.

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 a daily revisit time to every location on the planet with a huge footprint that is 77-km wide. The data is priced competitively with a base price 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 available 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.

Arapaho National Forest

The focus of this edition of Our Changing Landscape is a 575 square kilometer tract of mostly-forested mountain land up in the ‘hills’ above Boulder, Colorado. This piece of land straddles the Continental Divide – the point where water changes flow direction from east to west – with Arapaho National Forest running through the center. Arapaho National Forest covers 770,604 acres and is a wilderness lover’s dream, featuring miles of hiking trails through stands of spruce and aspen trees, mountain meadows and jagged peaks. Located just northeast of the center of the RapidEye images below are the Indian Peaks made up of three 13,000-feet plus mountains: Apache Peak (13,438 feet), Arapahoe Peak (13,392 feet) and Navajo Peak (13,405 feet).

In the southwest portion of these RapidEye images, you will see two small mountains towns: Fraser which is the larger of the two and then Tabernash located to the northwest at the edge of the scenes. Fraser is a town of about 1,000 residents and was settled in 1904 ahead of the arrival of the Moffat Railroad. Tabernash is a tiny town of less than 250 residents and is perhaps best known for a 1984 plane crash that was captured on VHS by a camcorder mounted on its instrument panel.

Located in the southeast corner of the RapidEye images is a local ski resort, Eldora. Eldora Mountain Resort is well known to the inhabitants of Boulder as it is our closest location to ski at just 21 miles away. The resort features 680 acres of skiable terrain with a 3-mile long run. Eldora averages 300 inches of snow per year, with the majority falling from December to February. During the winter of 2012 which is featured in the RapidEye images below, Eldora received just 200 inches of snowfall, well below its yearly average. The biggest snowfall of 24 inches was in early February with maximum base depth of 60 inches reached by early to mid-March. By mid-April, the base of snow was melted off and summer was on.

The RapidEye images that accompany this article cover a single winter season and show how much snow cover advances and retreats on a yearly basis in the Rocky Mountains. What you cannot see from this small snapshot in time is the disappearance of Colorado’s 14 named mountain glaciers. Mountain glaciers are particularly sensitive to small temperature and precipitation changes; and hence have been ravaged by global climate change. Located by the Indian Peaks is one glacier that is of particular importance to Boulder, Arapaho Glacier. It is part of the Silver Lake/Lakewood Watershed which supplies 40% of our drinking water and is rapidly shrinking. During the 20^th Century, Arapaho Glacier lost 52% of its surface area, decreasing from 0.34 square kilometers (sq km) to just 0.16 sq km. If the melting trend continues, Boulder will lose a significant part of its fresh water supply in as little as 60 years.

If you would like to find out more about using RapidEye for your academic studies, engineering projects or any landscape analysis, let us know at sales@apollomapping.com or (303) 993-3863.