The image would be saved to the phone, not the App? When uploaded to a database, it would be encoded in B64 format - a text based image description that is not human readable. That means it could potentially become part of the CSV string (not file) saved in the database, but we would need to know more about the database itself, it's capabilities.
This where the number of people involved in gathering survey data is critical to privacy and security. It would be made easier if they used phones dedicated to the survey and nothing else - is that doable?
..... another aspect is - how many people/families will be surveyed? Is this work backed by the government or is it independent of them?