GIS is used in many phases of disaster management starting with planning before an event happens. Disaster relief involves the response phase of disaster management. GIS and GIS professionals can assist immediately by helping decision makers understand the scope of the damage and identify locations where people may be trapped, injured, or require medical support and rescue.  Analyzing critical infrastructure (facilities essential for the operation and sustainability of health services, food services, and government operations) that is or could be damaged or destroyed is essential to restoring critical services and government operations.

Decision makers can assign response resources to the highest life safety and facility repair priorities.  Another critical mission that geospatial technology supports is emergency supply chain management.   

A few specific examples of how geospatial technology supports disaster relief include

• Rapid identification of potential shelter/housing locations (schools, libraries, churches, public buildings) appropriate for supporting affected populations.
• Identification of supplies and materials necessary for response, relief, and recovery efforts.
• Identification of locations suitable for staging areas and incident command posts (areas with the appropriate power, space, access, etc.) to provide logistical support for public safety personnel.
• If the disaster is persistent (flood, wildfire, chemical dispersion, weather event, etc.) GIS can model the speed, direction, and intensity of the event in order to warn people in harm's way or to position public safety resources for immediate deployment.
• GIS can produce maps and imagery of the incident for government officials at regional and national levels who are responsible for providing additional public safety, logistical, and financial resources support.

During large scale disasters in remote locations throughout the world (based upon the type of emergency or disaster), GIS is used to:

• Determine how many tents will be needed based upon the location of populations affected by the disaster.
• Analyze vulnerable populations for secondary health effects from a disaster, implementing inoculation and preventive treatments, and positioning medical teams and medical supplies in locations to optimize preventive treatments.
• Analyze areas where large numbers of refugees can establish camps out of harm's way, accessible for supply delivery, with access to water and other resources necessary to support large numbers of people.
• Identify where the appropriate relief supplies can be obtained, transported, and delivered to various refugee camps or where they are most needed (highways, bridges, sites suitable for landing fixed-wing or rotary aircraft, etc.).   
• Analyze security requirements to protect responders, refugees, and supplies.
• Maintain and display the status of the response, relief, and recovery efforts.

Disasters in the form of earthquakes, fires, floods, hurricanes, and tornadoes have severe economic, financial, and social impacts on communities.  Most disasters are characterized by short reaction/response times, overwhelming devastation to infrastructure, and a strain on the tangible and intangible resources of the affected community. Decision makers at local, state, and federal levels are expected to quickly implement plans to restore order and mitigate the aftermath of the disaster.  

GIS technology is used to collect, store, analyze, and share geospatial information needed by agencies to effectively support operations and restore disaster-affected communities. Properly trained emergency planners and geospatial analysts can use GIS for disaster relief operations. They can use GIS to implement measures such as establishing communications sites, restoring electrical power, and planning traffic routes to carry emergency supplies to critical facilities. In many cases specific datasets will not be available to accommodate every possible contingency that may arise in disaster operations. For geospatial analysts, the challenge is to quickly gather data and accurately fuse it together to provide actionable information in support of emergency managers.