20 Photogrammetry Interview Questions and Answers

Photogrammetry is a process of taking measurements from photographs. It is commonly used in surveying and mapping applications. If you are interviewing for a position that involves photogrammetry, you can expect to be asked questions about your experience and knowledge of the process. In this article, we review some of the most common questions you may encounter during your interview.

Photogrammetry Interview Questions and Answers

Here are 20 commonly asked Photogrammetry interview questions and answers to prepare you for your interview:

1. What is Photogrammetry?

Photogrammetry is the science of making measurements from photographs.

2. Can you explain what a pinhole camera model is and how it works?

A pinhole camera model is a simplified camera model that is often used for computer vision applications. The model assumes that the camera is a pinhole camera, which means that light can only enter the camera through a small hole. This hole is typically located in the center of the camera sensor. The pinhole camera model is a good approximation for many real-world cameras, and it is often used because it is relatively easy to mathematically model.

3. What are some of the limitations of using ground control points for photogrammetric mapping?

Ground control points are typically used in photogrammetric mapping in order to improve the accuracy of the map. However, there are a few potential limitations to using ground control points. First, if the ground control points are not evenly distributed throughout the area being mapped, then the accuracy of the map may be uneven as well. Additionally, if the ground control points are not accurately surveyed, then the accuracy of the map will be compromised. Finally, if the ground control points are not visible in the imagery being used for the mapping, then they will be of no use in improving the accuracy of the map.

4. How do you derive the forward intersection equation to calculate image coordinates in the context of photogrammetry?

The forward intersection equation is used to calculate image coordinates from known object coordinates. This is done by taking the known coordinates of an object and projecting them onto the image plane. The image coordinates can then be calculated by solving for the intersection of the projected lines.

5. Can you explain what a stereo pair is?

A stereo pair is two images of the same scene that have been captured from slightly different viewpoints. By looking at the two images side-by-side, the viewer can see the scene in three dimensions, as the brain fuses the two images together.

6. Why is it important to use an electronic distance meter when capturing images with a digital camera?

When capturing images with a digital camera for photogrammetry, it is important to use an electronic distance meter to ensure that the images are captured at the correct scale. This is especially important when trying to create 3D models from the images, as the scale is essential for creating accurate models.

7. Can you explain what the collinearity principle means in the context of photogrammetry?

The collinearity principle states that if two lines in space intersect at a point, then the lines that are parallel to those two lines will also intersect at that same point. This principle is important in photogrammetry because it is used to calculate the 3D coordinates of points from 2D images.

8. When building a 3D map, why is it important to find the intersection between two rays passing through the optical center of both images?

The intersection of two rays passing through the optical center of two images is the only point that is common to both images and therefore can be used to create a 3D map. If the intersection point is not found, then the 3D map will be inaccurate.

9. Is it possible to perform bundle adjustment on aerial photographs taken from close range? If yes, then why?

Yes, it is possible to perform bundle adjustment on aerial photographs taken from close range. The reason for this is that the photos taken from close range will have a higher level of detail, which will allow for a more accurate reconstruction of the scene.

10. What’s the difference between direct and indirect georeferencing?

Direct georeferencing uses GPS data to directly map images to real-world coordinates, while indirect georeferencing uses known control points to establish a relationship between images and real-world coordinates.

11. Can you explain what raster data is and how it relates to vector data?

Raster data is a type of data that is made up of pixels, or small squares. Vector data, on the other hand, is made up of points, lines, and polygons. Raster data is best suited for representing continuous data, like a photograph, while vector data is better suited for representing discrete data, like a map.

12. What are the various steps involved in creating a photogrammetric map?

The steps involved in creating a photogrammetric map are:

1. Select an area to be mapped and take photographs of it from different angles.
2. Use photogrammetric software to process the images and create a 3D model of the area.
3. Use surveying equipment to take measurements of the area and create a topographic map.
4. Use the 3D model and the topographic map to create a photogrammetric map.

13. What does the term precision mean in the context of photogrammetry?

The term precision in photogrammetry refers to the ability of the technique to accurately measure the position of objects in three-dimensional space. This is typically done by taking a series of photographs of an object from different angles and then using computer software to reconstruct the object in three dimensions.

14. What is meant by accuracy in the context of photogrammetry?

In photogrammetry, accuracy refers to the degree to which measurements made using the technique agree with the true values of the quantities being measured.

15. What needs to be done if there is an error while trying to adjust parameters during triangulation?

If there is an error while trying to adjust parameters during triangulation, the first thing that needs to be done is to check the image for any blurriness or other issues that could be causing the problem. Once the image has been checked and corrected if necessary, the triangulation process can be restarted.

16. Can you give me some examples of real-world applications where photogrammetry is used?

Photogrammetry is used in a variety of different fields, including surveying, engineering, architecture, and even forensics. It can be used to create 3D models of objects or landscapes, and can be used to measure distances and angles with a high degree of accuracy.

17. What is the best way to determine whether or not a photogrammetric survey was successful?

The best way to determine the success of a photogrammetric survey is to compare the results of the survey to known ground control points. If the results of the survey match up with the known ground control points, then the survey was successful.

18. What is your opinion on the future of photogrammetry? What changes would you like to see happen?

I believe that photogrammetry will continue to grow in popularity and become increasingly commonplace in a variety of industries. I would like to see it become more user-friendly and accessible to a wider range of people. Additionally, I think it would be beneficial if photogrammetry software was able to integrate more seamlessly with other types of software, such as CAD programs.

19. Can you explain how GPS receivers relate to remote sensing? What impact do they have on it?

GPS receivers are used in remote sensing to help determine the location of objects being observed. This information is then used to create a map or image of the area being surveyed. The accuracy of GPS receivers has a direct impact on the accuracy of the resulting map or image.

20. Can you explain what object segmentation is? Is it important in the context of photogrammetry?

Object segmentation is the process of identifying and isolating individual objects within an image. This is important in photogrammetry because it allows for the accurate measurement of objects within an image. If objects are not properly segmented, then the measurements taken from the image will be inaccurate.