tain high-resolution aerial imagery.a Once that became available, the HOT team created new jobs in the Tasking Manager, asking volunteers to further validate and improve the basemap of the Philippines. The Tasking Manager is the most visible validation step, but the OpenStreetMap ecosystem also crucially features a lot of automatic (machine-driven) validation. Map editing software (“JOSM”) automatically validates a user’s edits before upload, warning about improbable data, such as buildings overlapping, or rivers crossing without meeting. Other automated tools regularly scan the OpenStreetMap database and highlight potential problems. Experienced mappers often use these for post-moderation: They can fix or revert problematic edits, or contact the user directly. This workflow (combined with ongoing coordination and communication via email lists, blogs and wikis) provides a validation structure on top of OpenStreetMap’s human-driven community model. The model remains highly open, with no pre-moderation and a semiformal hierarchy of validators; yet it rapidly produces highly detailed maps that international response agencies find very valuable. Since the data are open, agencies responding to needs in the aftermath of Typhoon Haiyan have been able to use it in many different ways: They printed it out as maps; downloaded it to response teams’ SatNav units; used it to locate population centers such as villages; and analyzed it to understand patterns of disease outbreak. This rapidly updated map data can also be used by journalists with a bit of geodata knowhow; for example, to provide geolocated contextual information for data coming in from other sources such as tweets, to help validate claims about the relative impacts on different areas, or to produce infographics of the impact and spread of a disaster. a The original sentence was “Representatives of HOT also liaised with agencies/companies such as NASA, USGS and DigitalGlobe to obtain highresolution aerial imagery.” The correction was made in order to give credit to the main organisation which provided the imagery.” 85