A satellite image is essentially like a map — it is full of information people can interpret if they know how. Space monitoring and using satellite shots can give people plenty of information about how the cities are developing and how transport is moving. Pictures taken from space are used to forecast weather and keep an eye on any destructive disasters like fires and storms. But how do people get all that information from a simple picture? Below, we are listing tips from the Earth Observatory. They are written for an average user. In total, there five ways to analyse a satellite image.
Analysing satellite image scale
Just like maps, pictures taken from space may have different scales. When average people take a look at a satellite image map, they are usually interested in seeing places they know. No doubt, it is cool to zoom in on the picture of your house from space. But, such a detailed picture can never take a big picture into perspective.
NASA, on other hand, does not comprise wide-angle views for high level of detail. People who research and monitor the Earth are usually interested in whole ecosystems. Some of their shots may even cover an entire hemisphere. And, since any satellite image is essentially a digital picture, it consists of little dots called pixels. The number of these dots results in higher or lower picture resolution. For weather forecasting, geostationary space shots cover wide areas where one pixel can cover an area up to four kilometers. So, no weather satellite image can offer a detailed view of minor details.
Considering shapes and patterns
Another way to interpret a picture from space is to look for any familiar shapes and patterns. Lakes and rivers are the easiest to identify because they have distant shapes and pretty much the same on maps. Whenever you see a straight line, it is most obviously human-made — most likely a road. Forests are also quite easy to spot. Rectangular shapes are usually fields and farms. Mountains also have an easily recognisable shape on any picture. But, when looking for mountain ranges, mind a relief inversion. We expect the light to fall from the left side, but a satellite image can be taken when the light falls from the right. In this case, one can confuse a mountain range with a canyon.
Understanding picture colors
Color on an image taken from space can vary depending on its measurement instrument. Today, most satellites take true-color shots, meaning that we see familiar shades of green, brown, blue, and red. A satellite image like this looks familiar to the eye. Some images, on the other hand, are shot in infrared, creating a false-color effect.
Water is easiest to identify on any satellite image. With true color, most water bodies will have a familiar blue color. However, it may have silver or even white shades if a satellite image captures light reflection from the water surface.
Plants captured on most satellite images may have different shades. Obviously, evergreen plants remain green throughout the year, but plants usually change their shade from season to season. All seasonal changes are clearly seen in true-color satellite image.
Still, analysing satellite images is about context. Sometimes, clouds and shadows from mountain ranges can create optical illusions. So, it is always important to mind what it is the context of satellite images. This way, you should not confuse shadows for bodies of water.
Remember where the north is
Like maps, satellite images are north-oriented. The Earth Observatory that shared these tips always has north-markers on its satellite images. By default, north is always up. But, a google maps satellite image can be seen from different angles. Just like the Earth Observatory images, Google has a north arrow so that people would not get lost. Always mind what is a satellite image in the first place. It is a map, so use it accordingly.
Prior knowledge of the area is always helpful
It may be really hard to understand satellite images of unknown areas. So, your prior knowledge can be very helpful, especially if you consider that every satellite image of Earth is taken in real-time. However, the whole point of using satellites is to track and monitor any changes. For example, people use satellites to analyse geology patterns like volcanic activity. Satellite images are also used by chemists to monitor pollution levels. If you know that forest fire or volcanic eruption recently happened in the area you are looking at, it will be way easier to understand what you’re seeing.
As you can now see, analysing satellite images is not that hard as it seems. Essentially, it goes down to common sense. If you can read maps, finding your way through satellite images should not be that hard.