Quality control for crowdsourcing large scale topographic maps

Crowdsourcing is an emerging methodology for spatial data collection. This methodology has been used extensively to create small scale maps such as in OpenStreetMap. However, it has rarely been used in acquiring large scale, accurate engineering data. Expert-sourcing uses methods similar to crowdsourcing except that it collects information from experts and professionals. This article describes the development steps of novel expert-sourcing methodologies for updating the national geo-spatial database (cadastre and topography) in Israel. The input data for the process are building permit maps at a scale of 1 : 250 created by professionals. The first step in the process was the adaptation of a national standard for digital map contents, cartography and computer format. The second step was the development of the crowdsourcing system to get the maps from mapping professionals, assess them and verify that they meet the criteria. The two challenges in this step were to design an engaging User Experience (UX) that will not require training or a user manual and to develop automatic quality control tools. The third step was the creation of a data integration process to update the national database from the various sources. The system (aka TopoCad) provides a comprehensive set of tools to support the practice of obtaining information from all the surveyors and mapping experts in Israel. The system aggregates all the information of every mapping activity (geodesy, cadastre, construction permits, mapping and GIS) in a semi-automatic process. This novel platform improved governmental procedures and made services more efficient. In addition, this innovative tool improved the national databases by updating them with new data on an on-going basis.