I am trying to obtain an Homography of a soccer image shot by a broadcasting camera. The original picture:
I then proceed to find field lines, resulting in the following:
From what I understand, at least 4 points need to be detected. From the detected line, I should easily obtain 4 points by intersection of the lines. (I will extend the detected lines so they actually intersect)
The detected points can then be projected to another image. Since I do not have another image, I believe I should use a field model, like the one below.
Since field dimensions are known, every intersection point of the field model in world coordinates are known. For example: the middle of the field can be set to (0,0) (in meters). The top right of the field will then be (52.5,34) (in meters).
Now how do I set those world coordinates on the image?
Not exactly homography, but you could just use georeferencing in QGIS or ArcGIS, and look through the different projections. I've tried something similar with hockey, and georeferencing when players shot goals from.
from my previous reddit post on the subject:
I created a 200ft x 80ft rectangle over PNC arena in ArcGIS Pro using the North Carolina State Plane NAD 83 2011 revision, plus two 80ft x 11ft boxes at each end to make georeferencing the diagram in the official 2018-19 NHL Rulebook. Then, I took the screen grab of the play, and georeferenced the extremely oblique image to the georeferenced rink using a spline georeferencing. Larkin's goal was roughly 181 ft, 19ft short of the entire length of the ice.