Delineation of Vegetation Using Satellite Imagery, Clark County

Science Center Objects

In 2006, USGS, in cooperation with the Bureau of Land Management (BLM), began a 4-year study of the Red Rock Canyon National Conservation Area (NCA) to produce a land-cover data set from DigitalGlobe’s QuickBird high-resolution (2.4-meter) satellite imagery and field vegetation data. In 2010, the study was extended to include the Clark County portion of Mormon Mesa, and Coyote Springs and Piute-Eldorado Valley Areas of Critical Environmental Concern (ACEC).

Desert Tortoise, Red Rock Canyon National Conservation Area, Nev.
Desert Tortoise, Red Rock Canyon National Conservation Area, Nev. (Public domain.)

BLM administers more than half of the approximately 5 million acres of land in Clark County, Nevada. Federal lands are often designated for specific uses or protection, requiring manage­ment plans tailored to those designations. In 1990, the Red Rock Canyon NCA was designated as Nevada’s first National Conservation Area to protect and preserve geological, archaeological, ecological, cultural, scenic, scientific, wildlife, riparian, wilderness, endangered species, and recreation resources. The Coyote Springs, Piute-Eldorado Valley, and Mormon Mesa ACECs were designated to protect critical habitat for the desert tortoise (Gopherus agassizii).  The resolution and level of vegetation detail of existing land-cover data sets were not sufficient to support local resource management in these areas.

Vegetation sample plot, Clark County, Nev.
Vegetation sample plot, Clark County, Nev. Photo courtesy of David A. Charlet (Public domain).

Feature extraction software, Feature Analyst, was used to classify the imagery on the basis of detailed field data. Over 1,000 vegetation field samples were collected and classified to the National Vegetation Classification Standard, Version 2 hierarchy at the alliance level and above. Feature extraction models were developed for vegetation on the basis of the spectral and spatial characteristics of selected field samples by using the Feature Analyst hierarchical learning process. Individual model results were merged to create one data set for the Red Rock Canyon NCA and one for each of the ACECs. Field sample points and photographs were used to validate and update the data set after model results were merged. Non-vegetation data layers, such as roads and disturbed areas, were delineated from the imagery and added to the final data sets. The resulting land-cover data sets are significantly more detailed than previously were available, both in resolution and in vegetation classes.