Short Answer:

In surveying, aerial photography is used to capture images of the land from above using aircraft or drones. The main types of aerial photography used are vertical, oblique, and convergent. These different types help surveyors map land, measure distances, and plan projects with better visibility from the sky.

Vertical photography is taken with the camera pointing straight down, mostly used for maps and measurements. Oblique photography is taken at an angle and shows side views, useful for visual interpretation. Convergent photography involves two angled photos taken toward the same point for 3D modeling.

Detailed Explanation:

Types of aerial photography used in surveying

Aerial photography is a powerful tool in surveying because it helps collect detailed information about land without being physically present on the ground. It involves taking photographs from an elevated position using drones, aircraft, or helicopters. These photographs are then used to create maps, measure areas, monitor changes in terrain, and plan engineering projects.

The types of aerial photography vary based on the camera angle and purpose of use. Each type has its own importance depending on whether we need accurate measurements, general views, or three-dimensional models. The three main types of aerial photography used in surveying are vertical, oblique, and convergent photography.

1. Vertical aerial photography

Vertical photography is the most commonly used type in surveying. In this type, the camera is mounted in the aircraft so that it points straight down toward the ground. The result is a bird’s-eye view where the scale is nearly uniform across the image.

Key features:

• Provides a top-down view with minimal distortion.
• Ideal for creating accurate maps and land-use plans.
• Commonly used in photogrammetry for measuring distances, areas, and elevations.
• Overlapping vertical photos are used to create mosaics and 3D models.

Vertical aerial photography is very useful for civil engineering surveys, city planning, road alignment, and infrastructure design.

2. Oblique aerial photography

Oblique photography is taken at an angle, rather than straight down. The camera is tilted to capture both the ground and the sides of objects. It can be divided into:

• Low oblique: The horizon is not visible.
• High oblique: The horizon is visible.

Key features:

• Gives a more natural view of the land.
• Helps in identifying features like buildings, trees, and slopes.
• Useful for site inspections, environmental studies, and visual analysis.
• Less accurate for measurements due to distortion from the angle.

Oblique photos are often used in project reports, presentations, and public communications because they show a more realistic scene.

3. Convergent or stereoscopic photography

Convergent photography is a method where two or more photos are taken from different angles, aimed at the same point on the ground. This allows the creation of 3D views when the images are processed together.

Key features:

• Enables creation of detailed 3D terrain models.
• Useful in digital elevation modeling (DEM).
• Applied in advanced photogrammetry and precision mapping.

Surveyors use convergent photography in areas that require high accuracy in elevation, like hilly regions, construction sites, or mining areas.

Choosing the right type

The selection of aerial photography depends on the survey purpose. Vertical photography is best for maps and engineering work. Oblique is better for viewing and analyzing landscapes. Convergent is used when 3D data is needed. In many cases, more than one type may be used together to get complete data.

Modern drones now make it easier and cheaper to perform all types of aerial photography with high resolution and GPS tagging.

Conclusion:

The main types of aerial photography used in surveying are vertical, oblique, and convergent. Each type serves different needs—vertical for mapping, oblique for visual study, and convergent for 3D modeling. Using the correct type helps surveyors gather accurate and useful data for planning and construction in civil engineering.