Please read https://wiki.openstreetmap.org/wiki/Key:source for an explanation of the proper use of 'sources' in a Changeset.  'Survey' means you were 'there and saw it firsthand'. 'Local knowledge' means you have 'some affiliation with the area (resident, place of work, frequent visits) and knows this first hand or from others in the area.'

If I go there and map based on what I see, that's 'survey'.  If I map based on talking to the park superintendent, or local folks, that's 'local knowledge'.