Crowd-sourced crisis mapping is a relatively new phenomenon and platform that enables the collection and visualization of real-time crisis data submitted by users through social media tools and cellular technologies. Crisis maps are generally used by both state and nonstate actors for sense-making and as a reference point for action. The current crisis map visualizations only show the location documents such as reports or short messages have been generated from. Such a limited representation fails to immediately show important content, such as themes from a document and their changes over time. As a result, sense-making becomes time-consuming and cognitively demanding. I present a set of visualization tools: Geo-Temporal Tag Visualization (GTViz), Geo-Temporal Pies and Geo-SparkClouds that treat the tags on the crowd-sourced reports as spatio-temporal textual datasets and provide interaction tools to explore the content of the reports. I also demonstrate the value of such tools with case studies and a controlled user study.

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This presented work deals with crowdsourcing tools for mapping and filtering of data that are created by the Ushahidi, Inc. and ways of their use. Ushahidi and SwiftRiver platforms and hosted version of Ushahidi called Crowdmap are counted among the tools for crisis mapping; however, more and more they are also used for other topics or issues. The aim of this work is to subject to a critical point of view not only the Ushahidi platform as a tool, but also a number of significant or interesting projects in which it was used. Presented is also the recommendation, how to use Ushahidi to create a successful project and the other way round what to avoid, when you work with Ushahidi. The basic building elements of Ushahidi are crowdsourcing, citizen journalism, geospatial information, and in particular the work of volunteers. This work describes the role of these building elements in Ushahidi, and subjects to critical reflection also the problematic sides, which Ushahidi is struggling with. Following is the analysis of selected sample of Ushahidi and Crowdmap deployments, which deals with the thematic, geographical and time stratification of the maps in the sample. Some significant uses of Ushahidi with humanitarian and non-humanitarian purpose of the deployment are examined in the end.