I just thought I'd make a quick note here that not all imports result in 'dead data'.
I updated the New York City watershed recreation areas (see https://wiki.openstreetmap.org/wiki/Import:_NYCDEP_Watershed_Recreation_Areas for details of the import process) this evening. I did it by following the import process as outlined on that page up to loading the areas' geometry and tagging into PostgreSQL. I then threw together three scripts to identify areas that were new [that is, available from New York city, but not in OSM], deleted [in OSM but not listed in New York City's metadata], and retagged [timestamp of modification of the map of the area unchanged, but changes to the access restrictions]. The scripts in question are all available for inspection in the project's repository at https://chiselapp.com/user/kbk/repository/osm-nycdep-import/timeline. intake_rec_areas.tcl loads the database from the PDF files on the New York City website. id_deleted_units.sql queries the database and the local OSM mirror to determine what units must be deleted. id_changed_units.sql queries the database and the local OSM mirror to determine what units need to be reimported or conflated because their geometry has changed. id_changed_tags.sql queries the database and the local OSM mirror to determine what units need to be retagged because of changed access restrictions. The scripts identified: 3 units where the PDF file served up by the city was malformed 0 deleted units 10 new units 25 units with changed geometry 6 units with change access restrictions These numbers were small enough that I didn't trouble to design any sort of automation for conflation and replacement. Instead, for everything that changed, I simply checked that the unit was last updated by OSM user 'ke9tv-NYCDEP-import', and then did the work of replacing the making the changes in JOSM, one changeset per modified unit, exactly as I did in the oriignal import. I thought this note might be useful as an experience report. Thanks for reading this far!
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