diff --git a/etc/db/upgrades/upgrade24-v0.3.11-replace-augment-data-procedure.sql b/etc/db/upgrades/upgrade24-v0.3.11-replace-augment-data-procedure.sql
new file mode 100644
index 0000000..f9316b7
--- /dev/null
+++ b/etc/db/upgrades/upgrade24-v0.3.11-replace-augment-data-procedure.sql
@@ -0,0 +1,149 @@
+-- Fix not being able to edit a time-based event.
+--
+-- New schema version: 0.3.11
+--
+-- ATTENTION:
+--
+-- ENSURE YOU HAVE BACKED UP THE DATABASE BEFORE RUNNING THIS SCRIPT.
+--
+--
+-- NOTE: This upgrade affects only the public schema.
+-- NOTE: Each application starts a transaction, which must be committed
+-- or rolled back.
+--
+-- This redefines augment_event_data() to use interpolation rather than
+-- nearest neighbour. It now takes an argument indicating the maximum
+-- allowed interpolation timespan. An overload with a default of ten
+-- minutes is also provided, as an in situ replacement for the previous
+-- version.
+--
+-- The ten minute default is based on Triggerfish headers behaviour seen
+-- on crew 248 during soft starts.
+--
+-- To apply, run as the dougal user:
+--
+-- psql <<EOF
+-- \i $THIS_FILE
+-- COMMIT;
+-- EOF
+--
+-- NOTE: It can be applied multiple times without ill effect.
+--
+
+BEGIN;
+
+CREATE OR REPLACE PROCEDURE pg_temp.show_notice (notice text) AS $$
+BEGIN
+	RAISE NOTICE '%', notice;
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE PROCEDURE pg_temp.upgrade_survey_schema (schema_name text) AS $outer$
+BEGIN
+
+	RAISE NOTICE 'Updating schema %', schema_name;
+	-- We need to set the search path because some of the trigger
+	-- functions reference other tables in survey schemas assuming
+	-- they are in the search path.
+	EXECUTE format('SET search_path TO %I,public', schema_name);
+
+	CREATE OR REPLACE PROCEDURE augment_event_data (maxspan numeric)
+	LANGUAGE sql
+	AS $$
+		-- Populate the timestamp of sequence / point events
+		UPDATE event_log_full
+		SET tstamp = tstamp_from_sequence_shot(sequence, point)
+		WHERE
+			tstamp IS NULL AND sequence IS NOT NULL AND point IS NOT NULL;
+
+		-- Populate the geometry of sequence / point events for which
+		-- there is raw_shots data.
+		UPDATE event_log_full
+		SET meta = meta ||
+			jsonb_build_object(
+				'geometry',
+				(
+					SELECT st_transform(geometry, 4326)::jsonb
+					FROM raw_shots rs
+					WHERE rs.sequence = event_log_full.sequence AND rs.point = event_log_full.point
+				)
+			)
+		WHERE
+			sequence IS NOT NULL AND point IS NOT NULL AND
+			NOT meta ? 'geometry';
+
+		-- Populate the geometry of time-based events
+		UPDATE event_log_full e
+		SET
+			meta = meta || jsonb_build_object('geometry',
+				(SELECT st_transform(g.geometry, 4326)::jsonb
+				FROM interpolate_geometry_from_tstamp(e.tstamp, maxspan) g))
+		WHERE
+			tstamp IS NOT NULL AND
+			sequence IS NULL AND point IS NULL AND
+			NOT meta ? 'geometry';
+
+		-- Get rid of null geometries
+		UPDATE event_log_full
+		SET
+			meta = meta - 'geometry'
+		WHERE
+			jsonb_typeof(meta->'geometry') = 'null';
+
+		-- Simplify the GeoJSON when the CRS is EPSG:4326
+		UPDATE event_log_full
+		SET
+			meta = meta #- '{geometry, crs}'
+		WHERE
+			meta->'geometry'->'crs'->'properties'->>'name' = 'EPSG:4326';
+
+	$$;
+
+	COMMENT ON PROCEDURE augment_event_data(numeric)
+		IS 'Populate missing timestamps and geometries in event_log_full';
+
+	CREATE OR REPLACE PROCEDURE augment_event_data ()
+	LANGUAGE sql
+	AS $$
+		CALL augment_event_data(600);
+	$$;
+
+	COMMENT ON PROCEDURE augment_event_data()
+		IS 'Overload of augment_event_data(maxspan numeric) with a maxspan value of 600 seconds.';
+
+END;
+$outer$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE PROCEDURE pg_temp.upgrade () AS $outer$
+DECLARE
+	row RECORD;
+BEGIN
+
+	FOR row IN
+		SELECT schema_name FROM information_schema.schemata
+		WHERE schema_name LIKE 'survey_%'
+		ORDER BY schema_name
+	LOOP
+		CALL pg_temp.upgrade_survey_schema(row.schema_name);
+	END LOOP;
+END;
+$outer$ LANGUAGE plpgsql;
+
+CALL pg_temp.upgrade();
+
+CALL pg_temp.show_notice('Cleaning up');
+DROP PROCEDURE pg_temp.upgrade_survey_schema (schema_name text);
+DROP PROCEDURE pg_temp.upgrade ();
+
+CALL pg_temp.show_notice('Updating db_schema version');
+INSERT INTO public.info VALUES ('version', '{"db_schema": "0.3.11"}')
+ON CONFLICT (key) DO UPDATE
+	SET value = public.info.value || '{"db_schema": "0.3.11"}' WHERE public.info.key = 'version';
+
+
+CALL pg_temp.show_notice('All done. You may now run "COMMIT;" to persist the changes');
+DROP PROCEDURE pg_temp.show_notice (notice text);
+
+--
+--NOTE Run `COMMIT;` now if all went well
+--