Generally, the cost and time to complete a study will decrease as the study narrows. Information collected may come from national archives, military databases, war records, range maps, records of disposal, vessel logs documenting activities, nautical charts, sailing publications, records of previous incidents of recovered munitions, public documents, databases developed by private researchers, the recreational diving community, and other relevant sources. This information is sometimes available in geographic information system (GIS) databases that are accessible during the non-technical survey. As with all (risk) assessments, the UXO risk assessment should be considered a living document, periodically reviewed, and updated accordingly.