This paper introduces an innovative methodology for estimating crowd sizes at significant events, particularly focusing on protests. This method combines aerial photography with urban mapping to enhance accuracy in measuring participant numbers. Originating from the analysis of extensive social protests in Chile, this approach was notably applied to what was reported as the largest march, where mainstream media claimed attendance exceeded one million. However, utilizing this new methodology, we recalculated the figure to be 354,167, challenging previous estimations. This research offers a reliable, repeatable tool for quantifying attendance at large gatherings, shedding light on the dynamics of public mobilization and space utilization. It provides a framework for assessing the comparative mobilization strength of various social movements and can extend to other large public events like concerts and sports, helping to gauge public engagement levels. Accurate crowd size estimations can inform policymakers, leading to more informed decisions and fostering a dialogue-based relationship between authorities and the public. By understanding protest scales and impacts, policies can be more aligned with societal needs, promoting a more inclusive and participatory democratic environment. This article, therefore, not only presents a methodological advancement but also underscores its applicability in enhancing democratic governance and public policy formulation.