Update README

docs/ERD/README.md

@@ -4,7 +4,7 @@ The Entity-Relationship Diagram (ERD) provides a graphical representation of dat
 ## A global overview
 Auto generated Mermaid diagram using [mermerd](https://github.com/KarnerTh/mermerd) and [MermaidJs](https://github.com/mermaid-js/mermaid).
 
-[PostgSail SQL Schema](https://github.com/xbgmsharp/postgsail/tree/main/docs/ERD/postgsail.md "PostgSail SQL Schema")
+![PostgSail SQL Schema](https://github.com/xbgmsharp/postgsail/tree/main/docs/ERD/postgsail.md "PostgSail SQL Schema")
 
 ## Further
 There is 3 main schemas:
@@ -32,3 +32,25 @@ There is 3 main schemas:
   - functions
     - ...
 
+## Overview
+- Insert data into table metadata from API using PostgREST
+- Insert data into table metrics from API using PostgREST
+- TimescaleDB Hypertable to store signalk metrics
+- pgsql functions to generate logbook, stays, moorages
+- CRON functions to process logbook, stays, moorages
+- python functions for geo reverse and send notification via email and/or pushover
+- Views statistics, timelapse, monitoring, logs
+- Always store time in UTC
+
+## Ingest flowchart
+```mermaid
+graph LR
+    A[SignalK] -- HTTP POST --> B{PostGREST}
+    B -- SQL --> C{PostgreSQL}
+    C --> D((metadata trigger))
+    C --> E((metrics trigger))
+    D --> F{tbl.metadata}
+    E --> G{tbl.metrics}
+    E --> H{tbl.logs}
+    E --> I{tbl.stays}
+```