Monocular Cues Flashcards
What are the four Monocular Cues?
- Geometric Perspective
- Retinal Image Size
- Aerial Perspective
- Motion Parallax
(GRAM)
What is
Geometric Perspective?
(GRAM)
An object may appear to have a different shape when viewed at varying distances and from different angles.
Geometric Perspective cues include:
•Linear Perspective
•Apparent Foreshortening
•Vertical Position in the Field
(LAV)
What is
Linear Perspective?
(LAV)
Parallel lines, such as runway lights, power lines and railroad tracks tend to converge as distance from the observer increases.
What is
Apparent Foreshortening?
(LAV)
The true shape of an object or a terrain feature appears elliptical when viewed from a distance.
As the distance to the object or terrain feature decreases, the apparent perspective changes to its true shape or form.
What is
Vertical Position in the Field?
(LAV)
Objects or terrain features farther away from the observer appear higher on the horizon than those closer to the observer.
At night, crew members can mistake lights on elevated structures or lights on low flying aircraft for distant ground structures because of the lights of the higher vertical position in the field.
What is
Retinal Image Size?
(GRAM)
The brain perceives the actual size of an object from the size of an image focused on the retina.
Four factors are considered in determining distance using image size:
•Known size of an object
•Increasing or decreasing size of objects
•Terrestrial association
•Overlapping contours
(KITO)
What is
Known Size of an Object?
(KITO)
The closer an object is to the observer, the larger its retinal image size is.
The observer must know the actual size of the object in order to use this cue.
If actual size is unknown, distance would be determined primarily by motion parallax.
What is
Increasing or Decreasing Size of Objects?
(KITO)
If the retinal image size of an object increases, the relative distance is decreasing.
If the image size decreases, the relative distance is increasing.
If the image size is constant, the object is at a fixed relative distance.
What is
Terrestrial Association?
(KITO)
Comparing an object such as an airfield, with an object of known size, such as a helicopter, helps determine the objects size and apparent distance from the observer.
Objects ordinarily associated together are judged to be at about the same distance.
What is
Overlapping Contours?
(KITO)
When objects overlap, the overlapped object is father away.
This overlapping is especially important to consider at night during landing approach.
Lights disappearing or flickering in the landing area indicate barriers between the landing area and the helicopter.
What is
Aerial Perspective?
(GRAM)
The clarity of an object and the shadow cast by it are perceived by the brain and are cues for estimating distance.
Several aerial perspective factors are used to estimate distances. They are:
•Fading Colors or Shades
•Loss of Detail or Texture
•Position of a Light Source and Direction of a Shadow
(FLP)
What is
Fading of Colors or Shades?
(FLP)
Subtitle variations in color and shade are clearer the closer the observer is to the object.
However, as distance increases, these distinctions blur.
EXAMPLE:
- Far distance vision of a hill= all one color and no distinguishing shapes.
- moving closer to the hill= the shadows and colors become noticeable.
What is
Loss of Detail or Texture?
(FLP)
As a person moves further away from an object, discrete details become less distinct.
EXAMPLE:
Object close to you- fine details, robust colors
Object far from you- no details, solid color appearance.
Because of reduced illumination also decreases resolution, this cue will disappear shortly after sunset or be limited to close viewing distances.
What is
Position of a Light and Direction of a Shadow?
(FLP)
Every object will cast a shadow from a light source:
The direction in which the shadow is cast depends on the position of the light source.
If the shadow of a light source is toward the observer, the object is closer than the light source is to the observer.
What is
Motion Parallax?
(GRAM)
This cue to depth is a means of judging distances under reduced illumination.
Motion Parallax refers to the apparent motion of stationary objects as viewed by an observer moving across the landscape.
Near objects appear to move past or opposite the path of motion, far objects seem to move in the direction of motion or appear to remain fixed.
