Crowd size estimation at rallies and events has always been a contentious topic, often leading to exaggerated claims and heated debates. With the advent of machine learning (ML), however, we now have the tools to bring more accuracy and objectivity to these discussions. Machine learning algorithms can analyze images and videos to provide a more reliable count of people in a crowd, potentially putting an end to these disputes.

One well-studied approach in computer vision for this problem is known as "crowd counting." Techniques vary, but one common method involves annotating each head in an image and treating it as a regression problem. Another approach uses a sliding window to classify each patch of the image according to its density and then sums up the patches to get a total count. These methods have been refined over time and can provide fairly accurate estimates, even in densely packed crowds.

For those who are just tinkering with ML, there are also simpler methods that don't require sophisticated algorithms. For instance, you can use an overhead photo of the crowd, estimate the area it occupies, and then count the number of people in a small, representative section of that area. By multiplying this count to cover the entire area, you can get a rough estimate of the total crowd size. While not as precise as ML-based methods, this can still offer a ballpark figure that is more reliable than mere guesswork.

However, it's important to note that accuracy alone may not be enough to settle debates. As one commenter pointed out, even when faced with irrefutable evidence, people often cling to their beliefs. This is particularly true in politically charged environments where emotions run high. While a machine learning algorithm can provide a more accurate count, it may not necessarily change the minds of those who are deeply entrenched in their views.

In conclusion, using machine learning for crowd counting can significantly improve the accuracy of crowd size estimates and bring more objectivity to the discussion. Whether through advanced ML techniques or simpler estimation methods, these tools can help provide a clearer picture. However, the challenge remains in convincing people to accept these more accurate counts, especially when they contradict deeply held beliefs.