How do you calculate flight height?
To estimate the AGL, you will need to determine the average elevation of the terrain and subtract that from altitude above sea level. This will give you the average flying height above ground. Example: A camera with a 152 mm focal length takes an aerial photograph from a flying height of 2280m above ground level.
What effect does aircraft altitude have on aerial imagery?
A higher flight altitude results in a larger GSD in the imagery, resulting in fewer identifiable features and so a larger point spacing.
Why is altitude considered important when taking an aerial photo?
For a given focal length of an aerial camera, the higher the camera is, the larger the area each aerial photo can cover. However, photographs taken at higher altitudes will be severely affected by the atmosphere. This is particularly true when films sensitive to shorter wavelengths are used.
How is Photoscale calculated?
You can also calculate air photo scale at a particular point by solving the equation Sp = f / (H-h), where f is the focal length of the camera, H is the flying height of the aircraft above mean sea level, and h is the elevation of the terrain at a given point.
How high is a plane from the ground?
According to USA Today, the common cruising altitude for most commercial airplanes is between 33,000 and 42,000 feet, or between about six and nearly eight miles above sea level. Typically, aircraft fly around 35,000 or 36,000 feet in the air.
How high does a normal airplane fly?
Commercial aircraft typically fly between 31,000 and 38,000 feet — about 5.9 to 7.2 miles — high and usually reach their cruising altitudes in the first 10 minutes of a flight, according to Beckman. Planes can fly much higher than this altitude, but that can present safety issues.
What is Photogrammetry overlap?
Overlap: is the amount by which one photograph includes the area covered by another photograph, and is expressed as a percentage. The photo survey is designed to acquire 60% forward overlap (between photos along the same flight line) and 30% lateral overlap (between photos on adjacent flight lines).
Which of the following indicates the correct set of overlapping percentage?
The percentage of overlapping must be in a range of 55-60 %. Explanation: While combining the photographs taken by two adjacent flights, it might lead to side lapping. The entire area in the photograph must be examined stereoscopically. This can be done only when the photographs are taken by adjacent flights.
What is focal length in remote sensing?
The focal length effectively controls the angular field of view of the lens (similar to the concept of instantaneous field of view discussed in section 2.3) and determines the area “seen” by the camera. Typical focal lengths used are 90mm, 210mm, and most commonly, 152mm.
What is focal length in aerial photography?
Focal length: the distance from the middle of the camera lens to the focal plane (i.e. the film). As focal length increases, image distortion decreases. The focal length is precisely measured when the camera is calibrated.
What is crab and drift?
Crab occurs when the aircraft is not oriented with flightline. It causes a reduction in a stereoscopic coverage of the terrain. Drift is the result of not be able the unmanned aircraft to keep the planned navigation bearing.
What is meant by photographing by scale?
Scale is the ratio of the distance between two points on an image to the actual distance between the same two points on the ground. Scale is an important describing factor of vertical aerial photography.
What does Ground Sampling Distance on a drone mean?
Ground sampling distance is the distance between center points of each sample taken of the ground. Since we’re talking about digital photos in drone surveying, each “sample” is a pixel.
How is the resolution of an aerial image determined?
In digital cameras, we use the Ground Sampling Distance (GSD) to describe the resolution quality of the image while in film-based cameras we use the film scale. Aerial photographs were acquired from an altitude of 6,000 ft AMT (Above Mean Terrain) with a film-based aerial camera with lens focal length of 6 inches.
How big is a GSD on a drone?
In simpler terms, the GSD represents the size of one pixel on the ground. Below, you can see an AeroPoint captured 30m (~100ft) above the ground with a Phantom 4 RTK drone.
How to calculate the distance between flight lines?
Compute the coverage on the ground of one image (along the width of the camera CCD array (or W)) as we discussed in section 4.3. Line spacing or distance between flight lines (SP) = Image coverage (W) x (100 – amount of side lap)/100. Number of flight lines (NFL) = (WIDTH / SP) + 1.