diff --git a/Dev-Notes.md b/Dev-Notes.md
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+++ b/Dev-Notes.md
@@ -1,3 +1,20 @@
+## 20240117
+
+Example SQL query to convert Cayenne GPS location into PostGIS point:
+
+```sql
+WITH gps(alt, lat, lon) AS
+  (SELECT
+    CAST (object -> 'gpsLocation' -> '1' ->> 'altitude' AS FLOAT),
+    CAST (object -> 'gpsLocation' -> '1' ->> 'latitude' AS FLOAT),
+    CAST (object -> 'gpsLocation' -> '1' ->> 'longitude' AS FLOAT)
+  FROM event_up)
+SELECT ST_MakePoint(lon, lat, alt)
+FROM gps;
+```
+
+`CREATE EXTENSION postgis;` must be run on each database, not just the PostgreSQL instance.
+
 ## 20240116
 
 https://github.com/CrunchyData/pg_featureserv - a lightweight alternative to Geoserver for serving WFS3 (found from https://gis.stackexchange.com/a/379506)