Image Interpretation

Web-based GIS workshop for teachersSeptember 19, 2009

Where Do Images Come From?

• Aircraft– Aerial photos

• Satellites– Satellite imagery

Courtesy of the California Coastal Records Project

Source: Google Earth

Clues to Interpret Imagery

• Shape• Size • Pattern• Tone/Color• Shadow• Association

Shape

Man-made features tend to have straight edges; natural features do not

Which one of these is a river and which one is a canal?

Size

The size of an object can help you determine what it is.

Which is the school complex and which are the houses?

Pattern

Certain objects have distinct patterns. Man-made features tend to have regular patterns while natural features tend to have irregular patterns.

San Francisco

Mountain drainage patterns

Tone/Color

The brightness and variation of color can help you interpret the image.This image shows various types of agricultural crops.

Shadow

Shadows can provide information about an object’s height and shape

San Francisco

Association

Sometimes you can identify an object by what is surrounding it.

Which image is a mountain lake and which is a high desert lake?Which one is Lake Tahoe?

Spatial Resolution

• How much detail you can see on the ground

1m spatial resolution(Digital Globe and others)

30 m spatial resolution(Landsat Thematic Mapper)

Just For Fun…What Is This?

….And This?

Just One More…