Visual Interpretation - An Imagery Orientation

 Welcome to the first lab of the Aerial Photo and Remote Sensing course. This lab was a combination of 3 interrelated exercises. The first two were variations on a theme, how do you analyze and interpret features within an image. 

Utilizing visual tones and textures, we first identify areas that help provide visual contrast throughout the scene. That is the subject of the first map below. This map Utilizes an objective scale for tones transitioning from very dark, dark, medium, light, very light, and then textures from very course, course, mottled, smooth, very smooth. These were done by creating a new feature class and then manually digitizing the polygon containers for the specific features. I also personally feel the harder of the two to prescribe a clean break in scale is Tone. Especially when the entirety of the image is gray scale or panchromatic. 

This next graphic is very similar to the one above, but it focuses on visual characteristics broken down into four specific categories to help provide positive feature identification. The categories are shape/size, shadow, patterns, and local association. Examples for each category highlighted below include applying point features to obvious beach buildings based on their rectangular shape. The central water tower is more easily recognized because of the shadow it casts. Likewise, power poles and power lines all cast definitive shadows based on an illumination source to the south, southeast of the scene. For localized patterns the beach neighborhoods, parking lots, and roadways all provide definitive features based on this characteristic. Association is one of the more nuanced concepts, as it relies upon the relationship of surrounding objects or scene. For example, a long rectangular thoroughfare jutting into the water… really can only be a Pier in this context. Also, there are a couple of dark blotches surrounded by buildings or other features serving to highlight this central area. These are swimming pools in a courtyard.  

The third portion of the lab was a comparison between a True Color and False Color version of the same image.  This exercise was overall less involved in the technical aspects, as it focused on comparing two map frames, one True Color, one False Color, with 5 common reference points described above. The same technical skills as above were applied. Adding undefined imagery, and creating a new feature class, and then locating comparison points.

As an introduction to the differences between True and False color, this exercise served to highlight some broad differences in presentation with simple color band assignment changes. The water, forests, and certain man-made features provided the greatest contrast, often with the False Color causing the features to be more discernible.

The direct side by side of the images is below.

 

Thank you for your time, look forward to seeing you next lab!

v/r

Brandon