The Los Angeles Homeless Map, by the people of Cartifact.
“The purpose of the downtown Los Angeles Homeless Map is to visually tell the story of downtown’s homeless population. Before a problem can be solved it must be understood. These maps exist to convey the situation on the streets to City leaders, the Police Department and all those who are concerned with homelessness in our city.”
Visually efficient and the map-making process is documented here.