specify a number of “jobs” to be done - such as mapping the roads and buildings within a defined area - and divides each job into small square “tasks,” each manageable by one volunteer mapper by tracing from aerial imagery. During the Haiyan response, more than 1,500 mappers contributed, with up to 100 using the Tasking Manager at the same time. Dividing each job was crucial in order to make the best use of this surge of effort. After claiming a task, a user edits their area of OpenStreetMap and can then mark their task square as “Done” (the red squares in the picture). However, the Tasking Manager requires that a second, more experienced person survey the work done before the task can be marked as “Validated” (green). (If the task was not completed properly, the “Done” status is removed by the second person.) Mappers can leave comments on the task’s page, explaining reasons for unvalidating or highlighting any issues encountered in mapping. Aerial imagery is crucial to enable “armchair mappers” to contribute remotely by tracing roads, buildings and other infrastructure. Microsoft provides global Bing imagery for the use of OpenStreetMap editors, and this was used during Haiyan. Representatives of HOT also liased with the State Department Humanitarian Information Unit through the Imagery to the Crowd program and other agencies and companies, to ob84