We are working on a GIS extension to OHDSI and are trying to figure out where to put derived variables in regards to the CDM.
One of our goals is for users to be able to derive new variables using their own location data and external sources. A simple use case would be “distance to closest park” for each location. Another would be “how many supermarkets are within a 10 mile radius”. In a sense, they seem to be observations about locations. A more complicated scenario would be “what was the travel time from residence to care site for this visit”.
Should these exist outside of the CDM? Is there a standard way of incorporating external data?