Grade: 4- 6
Time Duration: one class period
geography, language arts, science, observation, spatial relationships
oblique, vertical, landforms, remote sensing imagery
A remotely sensed image can give us data about an area and its relationship to the areas around it or to areas anywhere that we choose to compare with it. But can we identify places that we know or recognize on an RSI? Imagine that you are flying over your town or neighborhood in an airplane. How could you find your hose? Your school? Where you shop? On an RSI we also use landforms and other features to help us pinpoint locations that we would like to study.
In order to accurately understand the relationship between colors and images on the RSI and the locations that they represent, scientists send teams to "ground truth" areas in the image. These teams travel to locations on the image and take photos and other readings of the area in order to set standards to interpret the differences on the RSI. For example, in the study of the Kesterson Reservoir , scientists discovered that the cattail population around the reservoir that show up as light green on an RSI that uses specific wavelengths have absorbed polluting minerals whereas the cattails that show up as dark green have not.
The first step to using an RSI is to be able to picture the type of area that is represented by given colors on the image. (Many RSI are not taken in visible light and so are displayed in false color which require false-color keys to interpret.) To start, students will identify features on a remotely sensed image then match locations pinpointed on the image with oblique images taken at each spot.
If you decide to take oblique photos of your area or another area for which you have obtained an RSI, then choose varied locations. At each location, take the photos near the same time of day and from the four cardinal compass points (N, W, E, W). When selecting photos to be used in class, choose images with the same orientation at each location. Students can then keep one orientation in mind when matching oblique images with points on the RSI.
Look at a ground-level photo of an area shown in your local RSI. Find one or more possible locations on the RSI where it could have been taken. Have students explain their choice.