Oh, the Places We Go!
Landsat has been observing our natural & built world for 50 years, revealing how people have changed the landscape on Earth.
What Landsat Sees
Imagine you are on a rollercoaster about to crest the top of the first big drop. There is that brief moment at the very top when you get an amazing view of the landscape around you. You can see across the park, the tall rides poking above the trees, and maybe even distant skyline of buildings.
As more rides are built and tourist attractions are created, the more tourists come to the area. More hotels and roads are needed. Schools, neighborhoods, and businesses are also needed to support the people living in the area including those sustaining the local tourist economy. This is what happened in Orlando, Florida over the past half century.
When Walt Disney was looking for a location for Disney World in the 1960’s, he decided on an area in Central Florida that was mostly swamp land at the time. By 1971, a year before the first Landsat was launched, Magic Kingdom was established near the city of Orlando. In the following decades, new theme parks were added with Epcot in 1982, Disney Hollywood Studios in 1989, and Animal Kingdom in 1998.
The construction of Disney World led to an increase in other business and attractions opening along Interstate 40, one of Florida’s major highways. SeaWorld Orlando opened in 1973 and added Discovery Cove in 2000. In 1990 Universal Studios opened and in 1999 added its Island of Adventure extension.
All this excitement has been observed by Landsat satellites since 1972. In these Landsat images, vegetation is green, water is black, and urban areas are white. The left image was acquired in 1976 by Landsat 3 and shows Magic Kingdom, SeaWorld, and the Orlando airport. As more new parks opened, we can see more shopping malls, roads, hotels, and even an expansion of the Orlando airport in this 2014 Landsat 8 image (right). The 2014 image shows more detail because of the advances in Landsat’s technology from Landsat 3 to Landsat 8.
The Landsat series of satellites continues to provide a consistent record of tourist destinations like Orlando and how the Earth is affected by urbanization.
Changes from Landsat
In less than the time it took between the establishment of Walt Disney World and the opening of their forth theme park Animal Kingdom, the city of Shanghai in China grew from just 119 square miles of urban area in 1984 (the size of Orlando today) to 503 square miles by 2014. This makes Shanghai China’s fastest growing city. In just nine years between 2000 and 2019, its population grew from 16.4 million people to over 22 million – about the same as the population of the entire state of Florida
This pair of Landsat images between the years 1984 (left) and 2019 (right) recorded Shanghai’s rapid growth and reveals how much the city’s footprint has increased. You can see urban areas (appearing as gray and white) expand in all directions with new housing, factories, shopping, and parking lots replacing what had mainly been green farmland and forests. This growth has altered some of Shanghai’s natural ecosystems – destroying wetlands in some areas and creating them in others.
As more wetlands, forests, and farmlands are replaced with concrete and buildings, the more the sun’s energy heats up the city – known as the urban heat island effect . Scientists also saw a rise in Shanghai’s temperature as a direct result of increased urbanization.
Data from Landsat’s thermal sensors showed that the temperatures in parts of Shanghai increased 81 percent between 1984 and 2014. They also found that urban greening efforts had slowed the growth of heat islands. The pentagon-shaped greenway, visible in the 2019 image, is part of a network of parks and forested areas built around a major highway. City planners established the greenway to give residents some access to green spaces. The added vegetation had another benefit; it had a cooling effect on the city.
Landsat data will continue to allow researchers to monitor Shanghai’s growth over time and observe the effects of urban expansion on surrounding ecosystems like wetlands.
Neighboring cities including Suzhou and Wuxi have slowly merged with Shanghai and now look like one enormous city.
How Change Affects Us
Have you ever walked barefoot on a hot summer day and noticed that walking on grass is cooler than walking on the concrete side walk? Or that the white painted stripes on a road are cooler than the black pavement? This is because surfaces like concrete, pavement, and dark colored surfaces absorb sunlight and heat up. We can feel this heat radiating off the surfaces like the coils of a space heater or stove top.
As cities grow, more land is developed into paved roads and parking lots, concrete and steel structures, and brick or block buildings with dark roofs. While this growth brings new places to shop, eat, play, and live, this change can also make some cities warmer.
We can see this urban heat island effect in Baltimore, Maryland. Land temperature data from Landsat (left) can be compared to a land cover map (right) showing what areas are developed – or urbanized. The warmest temperatures are in the same places where there is more development. Temperatures in the densely developed center are as much at 10 degrees Celsius warmer than the forests outside the city. Imagine a hot summer day of 30ºC (86ºF) could feel like 40ºC (104ºF) in the center of the city.
We can also see some cooler areas in Baltimore. Patterson Park and Druid Hill Park are both cooler because of their vegetation. Plants also absorb sunlight, but instead sunlight heating up like concrete, photosynthesis converts the sunlight into sugar. Plants respire water which also helps keep the ground cool.
Landsat data helps city planners and managers make better decisions about their city including planning more green space to keep their cities cooler in the summer.
How Landsat Helps
Landsat can help us do more than just show how places have changed. Landsat can also provide valuable data to help city planners make better decisions.
Looking at this Landsat image (left), we can see shapes and patterns that look like rivers, mountains, farms, and roads in and around the city of Portland, Oregon. But can we see exactly how much area is covered with buildings and roads? Or calculate how much wetland is along the river? Or monitor how much forests are changing?
To answer these questions, city planners rely on color-coded maps like this one (right) from the NationalLand Cover Database (NLCD) . It shows the different land cover types in the Portland area such as wetland, urban, cultivated crops or deciduous forest. To create these maps, Geological Survey (USGS) used Landsat data.
Using data from Landsat, scientists can tell different landcovers apart because Landsat’s instruments detect beyond the visible light our eyes can see – they can detect infrared light.
Whether we are looking at concrete, corn crops, wetlands, or a pine forest, each reflect light differently. A crop of soy beans and corn both look green because they reflect highly in the green wavelengths of light. But they also reflect infrared because the plant’s chlorophyll reflects infrared wavelengths of light. By measuring how much each specific wavelength of visible or infrared light is reflected or absorbed, Landsat can reveal differences in land cover that our eyes can’t – like whether we are looking at a crop of corn or soybeans.
The National Land Cover Database includes maps of the nation’s land cover color-coded into 16 land cover classes for seven years: 2001, 2004, 2006, 2008, 2011, 2013 and 2016. These classification maps help more than just city managers, but anyone who needs to monitor changes over time such as growing cities, harvesting and planting of crops, assessing forest health, or other information to make better decisions about our planet’s resources.
People of Landsat: William Pecora
“The course seems clear; we must make and execute bold plans to gather data on the Earth’s resources … and to accelerate the search for natural resources.” — William Pecora
Postcards from Camp Landsat
This week we visit the 3rd largest city in Italy - Naples. Founded by the Greeks, Naples city center is the largest in Europe (covering 1,700 hectares) with a history going back 27 centuries. Today, the sprawling Naples metropolitan area is home to around 4 million people.
Collect all five postcards from Camp Landsat starting with Week 1: People & Places !
The adventure continues at Camp Landsat with lots of fun and fascinating Landsat facts and activities.
