ERI Funded Projects: Shijie Guo using ‘geomasking’ for environmental health studies at Dartmouth!

This summer I was working under the guidance of Professor Xun Shi from Dartmouth College to develop a stand-alone tool for an improved geographically masking (geomasking) method for environmental health studies. In the field of environmental health studies, in order to protect patients’ privacy, the location data for each patient needs to be displaced from its original location. However, to study the spatial distribution of patients, the spatial pattern needs to be preserved during the geomasking process. Profess Xun Shi developed an improved method that integrates high-resolution population data to account for the spatial variation and population heterogeneity in the process of geomasking. This method is currently implemented by the Geo Mask tool in ArcHealth software package (can be accessed at, which can only be used within ArcGIS software. I helped Profess Xun developed a stand-alone application on Windows platform that can be accessed without ArcGIS for use of environmental health researchers and students. I have also added a coordinate transformation feature in the new geomasking tool to transform longitude-latitude coordinate to coordinate in a projected coordinate system (state plane system) for ease of computation.

This research opportunity was an excellent learning experience for me. I learned about projection systems used for mappings and how different projection systems have their own defects and are accurate only in certain areas of the world and that U.S. has developed different coordinate system for each state to minimize error in projection. During the process of developing the tool, I learned how to develop program and graphical interface using C# (a programing language developed by Microsoft) and how to make an application to implement the algorithm Professor Xun has. This experience taught me how to convert a detailed and topic-specific academic theory to an application or a tool that can be used by general public who don’t know much about the theory behind it. I believe this experience is beneficial for my future academic experience as now I have the knowledge of how to apply a theory or algorithm to build an application for users to use.


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