Critical nautical chart corrections are disseminated weekly via the U.S. Coast Guard in the form of a PDF document called the “Local Notice to Mariners.” Users of both paper and electronic nautical charts need to regularly apply these corrections to update their charts for safe navigation. This paper gives a detailed description of a tool, called ChUM (the Chart Update Mashup), that simplifies the process of combining nautical charts with the critical chart corrections and the U.S. Coast Pilot (an aid to navigation) using Google Maps. This georeferenced interface simplifies finding chart corrections for a specific chart and allows for filtering and sorting the data.