WorldPop and Flowminder used census data combined with GIS data (collaborating with CIESIN in some instances) to create databases of population and country data. In its collaboration with UNFPA, high resolution satellite imagery is pooled with "bottom-up" microcensus data collected in the field. By collaborating across sectors WorldPop is able to combine satellite data, census data, and microcensus data to develop more robust population and settlement datasets. Data is then made available online via WorldPop for the public to access and use. The data made available by and to UNFPA through their collaboration with WorldPop and Flowminder has significant opportunities to improve public health and humanitarian and development outcomes. This model, for instance, has helped build Nigeria's vaccination tracking system.