How Does Photogrammetry Work? A Guide to Aerial and Ground Techniques

We use the scientific method of photogrammetry to measure objects’ distances, sizes, and spatial dimensions. Photogrammetry aerial uses overlapping images to create accurate 2D and 3D models of objects and places in the real world. This method is useful in many fields, like construction, surveying, and archaeology, where accurate spatial data is important.

As technology has improved, photogrammetry has become easier to use and more useful, especially when combined with new tools like drones and special cameras. In this guide, we will discuss both aerial and ground photogrammetry methods and their applications in various fields.

Understanding Photogrammetry Overview

Photogrammetry is all about the process of getting accurate data from pictures. At its core, the method involves taking several pictures of a subject from various angles and then comparing the differences between them to figure out the subject’s shape, size, and location in space. You can do this using both air- and ground-based methods.

In both aerial and ground photogrammetry, accuracy depends on several factors:

• Camera Quality: High-resolution images allow for more detailed measurements.
• Overlap of Images: The greater the overlap between images, the more accurate the resulting models.
• Georeferencing: In some cases, GPS data is integrated into the process to provide real-world coordinates for the captured images.

Photogrammetry is a wonderful way to record information about buildings and landscapes without hurting them or changing them in any way. Photogrammetry is a flexible and accurate way to do things like surveying land or taking pictures of archaeological sites.

Aerial Photogrammetry Techniques

Drones or manned aircraft typically assist in aerial photogrammetry, which involves taking pictures from above. This method is excellent for quickly and accurately surveying large areas. An unmanned aerial vehicle (UAV) with high-resolution cameras that can take hundreds of pictures in a single flight is the main tool for this job.

Key Advantages of Aerial Photogrammetry:

1. Wide Area Coverage: Aerial photogrammetry can cover vast areas in a fraction of the time it would take using traditional ground methods.
2. Efficient for Difficult Terrain: In areas where the terrain is uneven, inaccessible, or hazardous, drones provide a safer alternative for capturing data.
3. High-Resolution Output: Drones can fly at low altitudes, allowing for high-resolution imagery that is crucial for detailed mapping and analysis.

How It Works:

Aerial photogrammetry takes multiple overlapping images from above. Special software then transforms these pictures into 2D orthomosaic maps or 3D models of the surveyed area. Ground control points (GCPs) often connect the model to known geographic coordinates, enhancing its accuracy in space.

Applications of Aerial Photogrammetry:

• Construction Site Surveys: Aerial photogrammetry is used in construction to create topographic maps of sites before building begins. These maps provide accurate data about the land, which is essential for project planning.
• Agriculture: Farmers use drone-based photogrammetry to monitor crop health, measure yields, and identify areas that need attention, all from a bird’s-eye view.
• Environmental Monitoring: Aerial photogrammetry is used to monitor coastal erosion, deforestation, and other environmental changes over time.

Ground-Based Photogrammetry Methods

Ground-based photogrammetry is great for taking pictures of smaller, more detailed objects, while aerial photogrammetry is great for large-scale surveys. This method captures images of a subject from various ground angles, subsequently transforming them into a 3D model or a detailed map.

Key Advantages of Ground Photogrammetry:

1. Detail-Oriented: Ground photogrammetry excels in capturing fine details, making it ideal for tasks like documenting buildings, statues, or archaeological artefacts.
2. Cost-Effective: With no need for aerial equipment, ground-based photogrammetry can often be done with a simple DSLR camera or smartphone.
3. Versatility: It can be used in both outdoor and indoor environments, from documenting historical buildings to scanning the interiors of tunnels or caves.

How It Works:

During in-ground photogrammetry, two or more cameras capture images of the subject from different angles. For the software to be able to find key features and put the images together into a 3D model, they need to overlap enough. Sometimes, combining photogrammetry and laser scanning can yield more detailed results.

Applications of Ground Photogrammetry:

• Architecture and Heritage Preservation: Ground-based photogrammetry is used to create detailed models of historic structures, allowing for digital archiving or restoration planning.
• Forensics and Accident Reconstruction: Investigators use ground photogrammetry to create accurate reconstructions of crime scenes or traffic accidents, providing valuable insights into events.
• Industrial Inspections: Ground photogrammetry can be employed in factories and power plants to create 3D models of machinery for inspection and maintenance purposes.

Combining Aerial and Ground Photogrammetry

Often, researchers combine photogrammetry techniques from the air and the ground to capture a comprehensive image of a place or object. Aerial photogrammetry in a construction project can capture the entire site, while ground photogrammetry focuses on specific buildings or equipment. Combining both methods ensures the capture of every detail, from large-scale topography to minute design details.

When surveyors combine all of these methods, they can provide their clients with the accurate, high-resolution data they need to make decisions in industries like construction, farming, and environmental management. 

The Significance of Photogrammetry Techniques

To get detailed information about space, photogrammetry is a strong and flexible tool that combines science and technology. You can use drones for surveys from above, or you can take pictures of a building or archaeological site from the ground up. Either way, photogrammetry is a quick and accurate way to turn photos into useful 2D or 3D models.

They can pick the best method for their needs and projects if they know how to use both aerial and ground photogrammetry. With new technologies constantly emerging, photogrammetry should be able to provide even more accurate and cost-effective solutions for many different fields in the future.