The old saying "A picture's worth a thousand words" is often repeated because it's often true. It may be particularly true of pictures of the Earth, taken from above.
"That's what spurred my interest, in fact -- that images can tell a story," said Michael Hernandez, associate professor in the department of geosciences at Weber State University, speaking of images taken by satellite or plane.
"Earth From Space," a Smithsonian Institution traveling exhibit of satellite images, opens Saturday at the Brigham City Museum-Gallery. Hernandez does not have any ties to the exhibit, but he knows the value of such pictures.
The display of 41 large banners features colorful satellite imagery collected over the past 30 years. The exhibit also includes a digital video globe showing ocean temperature, weather patterns and other information collected using satellites.
Hernandez teaches classes on remote sensing, or observing the planet from a distance. "I meet a lot of folks who just enjoy looking at imagery and admiring the landscape," he said.
Those folks likely would enjoy the exhibit's satellite pictures of the Earth at night, with a spider web of bright lights spread across Europe, and images of the Great Pyramids and Victoria Falls.
Although often beautiful, satellite images are also used for practical purposes, to study everything from geography to biology.
Along the Wasatch Front, Hernandez says, satellite images can reveal information about faults and landslide areas.
"We don't want to build on top of a fault," for example, said Hernandez, adding that remote sensing allows scientists to identify areas that need to be studied more closely.
"We, as humans, still have to make wise decisions. We may choose to ignore it," he said, "but at least we're informed."
Researchers also can compare satellite images of the same area over a long period of time, to see how it's changed.
Visitors to the exhibit can check out satellite images taken 25 years apart, of Brazil's Amazon rain forest. One image shows a "fish bone" pattern of early deforestation; another shows more significant loss of plant life.
Locally, Hernandez is involved in a project using remote sensing to classify vegetation in the Uinta mountains.
"Down the road, 10 to 20 years, we'll see how the ecosystem has or hasn't been affected by climate change," he said.
Remote sensing can also be used to observe oceans, human activity and the global climate.
One banner in the exhibit shows forest fires in California -- images that couldn't have been captured on the ground.
"There are a lot of commercial satellites out there, that provide very high resolutions," Hernandez said. "City and county governments are using them as base maps for street center lines and locations of properties."
Understanding the images can be a challenge.
"It's all about observation -- just sitting there, looking at the image," said Hernandez. "What we see is based on a couple of things: 1) knowledge, and 2) our experience."
Satellite images captured using visible light reveal colors as we would see them with the eye: "Green is probably vegetation, the area that's light brown is probably bare or solid rock," said Hernandez.
But satellites also capture images using infrared and near-infrared wavelengths, as well as ultraviolet and microwave wavelengths. In these cases, observers need to know that things may not appear in their familiar colors.
"Vegetation in the visible part of the electromagnetic spectrum appears green, because it's reflecting visible green light," Hernandez explained. "We see it as green because we don't see the red and blue, because it's absorbing that for photosynthetic activity."
In a near-infrared image, vegetation may appear red.
"It's not based on photosynthesis, but on the health of leaf structure," said Hernandez.
The colors in these images may seem strange to untrained eyes, but Hernandez says the information presented by remote sensors using nonvisible wavelengths allows people to pick up on more subtle variations.
For gallery visitors who enjoy the exhibit, and want to see more, Hernandez suggests checking out the Utah GIS (Geographic Information Systems) Portal, www.agrc.utah.gov, a statewide geographic information database.
"It's exciting, and it's fun," Hernandez says of examining images made through remote sensing. "I can determine what I think I see in there. It's a way of exploring the landscape from home."