Falls Church image analysis and urban planning firm Digital Design & Imaging Service captured this photo of the Women’s March on Washington, D.C. last Saturday. The photo was taken by a specialized tethered surveillance balloon using a proprietary camera at 525 feet at 2:46 p.m. on Jan. 21.

According to DDIS, this elevated perspective is used to help calculate the relative density, coverage area and location of the event’s crowds as they crossed the National Mall (center) to Pennsylvania Ave (right). Currently, DDIS is teaming with British crowd scientists to objectively quantify the turnout of the march. When available, their data, methodology and images sources will be made available to the general public to encourage the public to draw their own conclusions about the event’s size.