Finding geographic coordinates of a camera picture pixel

Question

I'm trying to find the geographic coordinates of pixels though a camera picture. I have the camera coordinates, the azimuth and elevation of it. I also have the FOV of the image. In my web application I want to hover the image and for each pixel I want the lat lon, altitude and distance. After some research on the internet I was able to find similar questions (Calculating world coordinates of a pixel from a camera picture), but they are not very helpful for my problem as I need to use a digital terrain model. I just want to know the name of the technique for further investigation.

Answer 1

The technique you are referring to is often called "Photogrammetry." Photogrammetry is the science and technology of making measurements from photographs. It involves extracting geometric information from 2D images to generate 3D data.

In your case, you have camera coordinates, azimuth, elevation, and FOV. With this information, you can perform photogrammetric calculations to determine the geographic coordinates (latitude, longitude), altitude, and distance of pixels in the image.

To achieve this, you would typically use a combination of the camera's pose parameters, intrinsic parameters, and a digital terrain model (DTM). The DTM provides information about the elevation of the terrain at different points, allowing you to relate pixel coordinates in the image to real-world geographic coordinates.

For your specific task, you might want to explore the following steps:

1. Camera Calibration:

   • Calibrate your camera to obtain intrinsic parameters (focal length, principal point, etc.).

2. Photogrammetric Reconstruction:

   • Use the camera's pose (position, azimuth, elevation) and intrinsic parameters to reconstruct 3D points from 2D image points.

3. Digital Terrain Model (DTM):

   • Incorporate a DTM to account for the elevation of the terrain.

4. Coordinate Transformation:

   • Transform the 3D points into geographic coordinates (latitude, longitude, altitude).

This process requires careful consideration of the accuracy of your camera calibration, the quality of the DTM, and the overall photogrammetric workflow. There are software libraries and tools available that can assist with these calculations, such as OpenCV, Photogrammetry software like Pix4D or Agisoft Metashape, and GIS tools like GDAL.

Keep in mind that the accuracy of your results will depend on the quality of your input data and the calibration process.