Short Answer:
Photogrammetry in surveying is a method of measuring and mapping objects or land features by taking photographs from cameras placed on the ground or in the air. By analyzing these images, surveyors can determine the shape, size, and position of objects without physically touching them.
This technique is very useful for creating maps, measuring distances, and capturing data from hard-to-reach areas like mountains, forests, or construction sites. It saves time, reduces fieldwork, and provides accurate results using modern technology like drones and satellites.
Detailed Explanation:
Photogrammetry in surveying
Photogrammetry is a modern surveying method that uses photographs to collect accurate information about the shape, position, and dimensions of physical objects or land surfaces. It involves capturing images using cameras and then analyzing them to extract measurements. The word “photogrammetry” comes from three parts: photo (light), gram (drawing), and metry (measurement)—meaning measuring through images.
In surveying, photogrammetry is used to prepare maps, measure distances, calculate areas, and even create 3D models of the terrain. It is especially helpful in large or difficult areas where traditional surveying with instruments is time-consuming, dangerous, or not possible.
How photogrammetry works in surveying
The process starts by capturing multiple overlapping photographs of a site from different angles. These can be taken using handheld cameras, aircraft, or drones. For accurate results, surveyors ensure that the photos have enough overlap (usually around 60–80%) and are taken with good lighting and stability.
Once the images are captured, they are processed using specialized photogrammetry software. This software matches points in overlapping photos and calculates their actual positions in space using geometry principles, especially triangulation. This allows surveyors to recreate the position and size of each point on the ground.
There are two main types of photogrammetry used in surveying:
- Aerial photogrammetry – Uses cameras mounted on aircraft or drones to capture large areas from above. It is commonly used for mapping cities, agricultural land, forests, and roads.
- Terrestrial photogrammetry – Uses cameras on the ground to measure buildings, structures, or small sites. It is useful in construction, architecture, and historical site documentation.
Applications in civil engineering
Photogrammetry is widely used in many areas of civil engineering:
- Topographic mapping – Creating detailed contour maps of land for roads, dams, and construction projects.
- Land surveying – Measuring distances, boundaries, and features of plots or landscapes.
- Monitoring changes – Tracking changes in terrain, erosion, or building progress over time.
- 3D modeling – Producing three-dimensional views of sites for design and analysis.
- Infrastructure planning – Helping engineers in planning roads, bridges, and buildings by providing accurate site details.
Advantages of photogrammetry
- Fast data collection – Large areas can be surveyed quickly.
- Safe and remote access – Ideal for rough, high, or dangerous locations.
- High accuracy – Produces reliable measurements when done correctly.
- Cost-effective – Reduces manpower and field time.
- Visual record – Provides clear visual data for planning and documentation.
However, results depend on clear images, good weather, and proper calibration of the camera. Also, software processing requires skill and computer power.
Conclusion:
Photogrammetry in surveying is a powerful technique that uses photographs to measure and map land and structures. It helps surveyors collect accurate data from the ground or air without direct contact. This method is widely used in modern civil engineering due to its speed, safety, and precision, making it a key part of today’s surveying practices.