GIS4035 Module 2 - Aerial Photography Basics & Visual Interpretation of Aerial Photography

Map 1 - Degrees of Texture and Tone in an Aerial Image

Module 2 focused on the basics of aerial photography (vantage points, cameras, filtration, and films) along with how to use recognition elements to interpret aerial imagery. Recognition elements include location, tone and color, size, shape, texture, pattern, shadow, height/depth, and site, situation, and association. The first map depicted here focuses on the identification of different degrees of tone (from very light to very dark) and texture (from very fine to very coarse). Degree of tone indicates the degree of energy reflected by surfaces. Degree of texture is relative for any particular image. For this specific image, the texture ranges from very fine for water to very coarse for residential neighborhoods. For another image, these descriptions may vary significantly dependent on the nature of the subject of that particular image.

Map 2 - Features Identified by Visual Attributes

The second map focuses on utilizing other recognition elements to identify specific objects in the image. Shape and size were utilized to identify roads (long and linear), a pool (roman shape with rectangular diving board), and cars (rectangular shapes associated with large, open parking area). Shadows were used to identify a water tower (long, thin shadow with flared bottom and topped with bulbous shape), trees (slender trunks topped by clusters of fronds/branches), and a warning siren (horn-like shadow at top of tall, slender shadow which was distinctly different from the shadows of other poles in the image). Objects identified by patterns included parking spaces (herringbone pattern), utility poles (regularly spaced tall, thin objects with cross bars at the top), and houses (buildings of similar size, height, and spacing with a driveway to each structure). Some features were identified by their association with other features. This included the pier (a long, thin structure projecting from the shoreline out into the water with a shadow indicating height above the water) and a driveway (a short linear object which did not cast a shadow and leads to a house).

From personal and professional (surveying) use of aerial imagery, identification of objects is a rather comfortable practice. An area of growth for me was demonstrated in the third part of the lab which focused on comparing objects between a true color image and a false color infrared image. Along with learning more about the use of recognition elements in identifying objects in imagery, learning to interpret information from natural color and false color IR images is a skill I look forward to developing.