identification of a specific land use class (transportation) within an urban region
(City of Roanoke, Virginia, USA).
In addition to identifying specific land use classes, aerial photos enable time
series mapping of land use changes, an important analysis to identify how land use
has impacted water quality and quantity. Figure 3 (noted earlier) shows a comparison of the northwestern part of the City of Roanoke from 1960 to 2011. The 1960
photo shows some urban development for residential areas but also large expanses
of agricultural lands.
The two later images in Fig. 3 (2008 and 2011) show that urban land has replaced
former agricultural lands and includes additional residential areas throughout the
region, an airport, a large shopping mall, and other commercial areas. This time
series shows that permeable land surfaces have been extensively replaced by impervious surfaces, greatly altering the hydrologic characteristics of the land. These
changes, agriculture to urban, have greatly degraded the water quality of streams
within the Roanoke River watershed. The City of Roanoke has substantial drainage
problems and experiences frequent flooding due to increased stormwater runoff from
impervious surfaces. The Virginia Department of Environmental Quality has listed
several segments of the Roanoke River system within the city as impaired, i.e., they
do not meet established water quality standards due to the presence of contaminants
such as Escherichia coli, heavy metals, and high water temperature [34].
4.3 Mapping Using Satellite Imagery
The 1950s was the beginning of a race into space as governments across the world
established satellite systems for telecommunications, defense initiatives, and
weather monitoring. During the 1960s, astronauts from the US’ Gemini and Apollo
missions created a large archive of photos of the Earth from space. In the late 1960s,
one of the first broad-scale land cover maps was created from these photos
[35]. This map, of the southwestern United States, demonstrated the capability of
remotely sensing land cover employing imagery acquired from outside the Earth’s
atmosphere.
Weather satellites can be used to monitor the Earth’s surface, but their major
purpose is monitoring weather patterns using data at coarse spatial resolutions,
relative to the needs for land surface analysis. The first land observation satellite
was launched in 1972 (Landsat 1), a joint project of the USGS, the USDA, and the
US National Aeronautics and Aerospace Administration (NASA). With the advent
of land observation satellites, land use/land cover mapping and monitoring changed
dramatically. This system established the utility of satellites to acquire imagery
over large areas, to provide a continuous stream of images, and to record multitemporal images over the same area.
Land Use/Land Cover Monitoring and Geospatial Technologies: An Overview
13
(City of Roanoke, Virginia, USA).
In addition to identifying specific land use classes, aerial photos enable time
series mapping of land use changes, an important analysis to identify how land use
has impacted water quality and quantity. Figure 3 (noted earlier) shows a comparison of the northwestern part of the City of Roanoke from 1960 to 2011. The 1960
photo shows some urban development for residential areas but also large expanses
of agricultural lands.
The two later images in Fig. 3 (2008 and 2011) show that urban land has replaced
former agricultural lands and includes additional residential areas throughout the
region, an airport, a large shopping mall, and other commercial areas. This time
series shows that permeable land surfaces have been extensively replaced by impervious surfaces, greatly altering the hydrologic characteristics of the land. These
changes, agriculture to urban, have greatly degraded the water quality of streams
within the Roanoke River watershed. The City of Roanoke has substantial drainage
problems and experiences frequent flooding due to increased stormwater runoff from
impervious surfaces. The Virginia Department of Environmental Quality has listed
several segments of the Roanoke River system within the city as impaired, i.e., they
do not meet established water quality standards due to the presence of contaminants
such as Escherichia coli, heavy metals, and high water temperature [34].
4.3 Mapping Using Satellite Imagery
The 1950s was the beginning of a race into space as governments across the world
established satellite systems for telecommunications, defense initiatives, and
weather monitoring. During the 1960s, astronauts from the US’ Gemini and Apollo
missions created a large archive of photos of the Earth from space. In the late 1960s,
one of the first broad-scale land cover maps was created from these photos
[35]. This map, of the southwestern United States, demonstrated the capability of
remotely sensing land cover employing imagery acquired from outside the Earth’s
atmosphere.
Weather satellites can be used to monitor the Earth’s surface, but their major
purpose is monitoring weather patterns using data at coarse spatial resolutions,
relative to the needs for land surface analysis. The first land observation satellite
was launched in 1972 (Landsat 1), a joint project of the USGS, the USDA, and the
US National Aeronautics and Aerospace Administration (NASA). With the advent
of land observation satellites, land use/land cover mapping and monitoring changed
dramatically. This system established the utility of satellites to acquire imagery
over large areas, to provide a continuous stream of images, and to record multitemporal images over the same area.
Land Use/Land Cover Monitoring and Geospatial Technologies: An Overview
13