Update Dev Notes

Dev-Notes.md

@@ -31,7 +31,13 @@ GRANT SELECT ON tbeam TO qgis;
 
 Reception was dramatically better when the hotspot was on the roof. Graduated symbology worked fine in QGIS.
 
-Next step: set up `NOTIFY` triggers in Postgres and enable them in QGIS: https://kartoza.com/blog/postgis/using-notify-to-automatically-refresh-layers-in-qgis
+Next steps:
+
+- set up `NOTIFY` triggers in Postgres and enable them in QGIS: https://kartoza.com/blog/postgis/using-notify-to-automatically-refresh-layers-in-qgis
+- QGIS elevation data
+  - https://docs.qgis.org/3.34/en/docs/user_manual/map_views/3d_map_view.html
+  - https://www.qgistutorials.com/en/docs/working_with_terrain.html
+  - https://earthexplorer.usgs.gov/
 
 ## 20240117