Photogrammetry and Vertical Photo Measurements Flashcards
Photogrammetry definition
the science and technology of obtaining reliable spatial measurements and geometric information about surface objects and phenomena through the process of recording, measuring, and interpreting remotely sensed data and imagery
RS & Photogrammetry Differences (List)
Imaging system
Data
Application
RS & Photogrammetry Differences (Imaging system)
RS uses multispectral sensors to observe wavelengths
Photogrammetry uses image systems (DSLR, LiDAR) to observe images, not necessarily EMR
RS & Photogrammetry Differences (Data)
RS deals with 2D only
Photogrammetry deals with 2D AND 3D
RS & Photogrammetry Differences (Application)
RS analyzes and interprets images for understanding of land, water, and resources
Photogrammetry determines spatial properties and dimensions of objects in images
2 main branches of photogrammetry
Metric and Interpretative
Metric Photogrammetry definition
makes precise measurments and evaluates exact sizes, shapes, elevation, etc of surface features
Interpretative Photogrammetry
recognizing and identifying surface objects and judging their significance rather than making direct measurements and calculations
Types of aerial photos
Vertical - looking straight down, Nadir = PP
Oblique - taken at an angle
Elements of Aerial Photos
Principal Point (PP) - center of photo
Nadir
Field of View
Optical Axis
Nadir
The point on the ground directly underneath the sensor when an image is taken
Low Oblique vertical photo
Taken at an angle, no horizon shown (all ground)
High Oblique vertical photo
Taken at an angle, horizon shown
Photo Scale
Photo Distance / Ground Distance
Both values must be the same unit
Representative fraction
Relief Displacement definition
the shift in an object’s image position caused by its elevation above particular datum
displacement is in a direction radial from the principal point or nadir in vertical photos
Objects appear to lean
