Types of UAS Imagery; Imagery ground coverage and scale

Vocabulary flashcards covering types of UAS imagery, photogrammetry terminology, and calculations for ground sample distance.

Vertical (Nadir) Imagery

Imagery obtained when the camera’s optical axis is within sentiments $\pm 3^{\circ}$ of being vertical (perpendicular) to the Earth’s level surface.

Low-Oblique Imagery

Tilted aerial photography where the camera's optical axis deviates more than a few degrees from vertical and the horizon is not visible.

High-Oblique Imagery

Aerial photography where the camera is heavily tilted and the horizon is visible, often used for visualization and situational awareness.

Planimetric Maps

Maps focused on $(x,y)$ locations of natural features such as stream networks and rock outcrops.

Topographic Maps

Maps representing $(z ext{-elevation})$ above sea level.

Orthophotographs

Aerial photographs that are geometrically accurate in $(x,y)$ coordinates.

Photogrammetry

The art and science of making accurate measurements, such as object height, length, and area, by means of aerial photography.

Ground Sample Distance (GSD)

The size of the ground area captured by one pixel in an image, or the amount of actual ground captured by the distance between the center point of two adjacent pixels.

Pixel Size

A property of the sensor hardware referring to the physical dimension of a pixel on the camera sensor, measured in micrometers ($\mu m$).

Spatial Resolution

The smallest object that a sensor can reliably detect or distinguish, describing the level of detail visible in the image.

Flightline

A series of vertical photographs obtained by mounting a camera in a platform and taking overlapping photographs of the terrain directly beneath at specific exposure stations.

GSD Calculation Formula

An equation where $GSD = \frac{\text{Flight height} \times \text{Pixel size}}{\text{Focal length}}$, used to determine the scale and detail of a mapping project.

Digital Elevation Models (DEMs)

A purpose of aerial photography that provides a digital representation of terrain elevations.

Imagery Ground Coverage

The area captured on the ground, controlled by altitude, sensor size, and focal length.