diff --git a/handbook/troggle/trogmermaid.html b/handbook/troggle/trogmermaid.html
new file mode 100644
index 000000000..cb3e341c6
--- /dev/null
+++ b/handbook/troggle/trogmermaid.html
@@ -0,0 +1,73 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
+<title>Handbook Troggle Data Model</title>
+<link rel="stylesheet" type="text/css" href="../../css/main2.css" />
+ <script src="https://cdn.jsdelivr.net/npm/mermaid/dist/mermaid.min.js"></script>
+ <script>mermaid.initialize({startOnLoad:true});</script>
+</head>
+<body><style>body { background: #fff url(/images/style/bg-system.png) repeat-x 0 0 }</style>
+<h2 id="tophead">CUCC Expedition Handbook - troggle</h2>
+<h1>Troggle Data Model (python)</h1>
+<p>Asking ChatGPT to read our data model and produce a Mermad-style diagram produces something it has hallucinated. This is NOT troggle.
+<p><em>Can you look at the data model at https://expo.survex.com/handbook/troggle/datamodel.html and generate the data model in mermaid script in html</em>
+ <div class="mermaid">
+ graph LR
+ Cave --"1"--> Survey
+ Cave --"1"--> Map
+ Cave --"0..*"--> Expedition
+ Cave --"0..*"--> SurveyTeam
+ Cave --"0..*"--> Entrance
+ Cave --"0..*"--> Passage
+ Survey --"0..*"--> SurveyHeader
+ Survey --"0..*"--> SurveyStation
+ Survey --"0..*"--> SurveyFix
+ Survey --"0..*"--> SurveyFlag
+ Survey --"0..*"--> SurveyTeam
+ Survey --"0..*"--> SurveyInstrument
+ Survey --"0..*"--> SurveyCenterline
+ Survey --"0..*"--> SurveyShot
+ Survey --"0..*"--> SurveyCalibration
+ Survey --"0..*"--> SurveyExtra
+ Survey --"0..*"--> SurveyEquate
+ Expedition --"1"--> ExpeditionLeader
+ Expedition --"0..*"--> ExpeditionMember
+ Expedition --"0..*"--> ExpeditionEquipment
+ Entrance --"1"--> EntrancePosition
+ Passage --"0..*"--> PassagePoint
+ Passage --"0..*"--> PassageSection
+ </div>
+
+
+ <div class="mermaid">
+ graph LR
+ SurveyFile --"1"--> SurveyHeader
+ SurveyFile --"1"--> SurveyStation
+ SurveyFile --"1"--> SurveyFix
+ SurveyFile --"1"--> SurveyFlag
+ SurveyFile --"1"--> SurveyTeam
+ SurveyFile --"1"--> SurveyInstrument
+ SurveyFile --"1"--> SurveyCenterline
+ SurveyFile --"1"--> SurveyShot
+ SurveyFile --"1"--> SurveyCalibration
+ SurveyFile --"1"--> SurveyExtra
+ SurveyFile --"1"--> SurveyEquate
+ SurveyHeader --"1"--> SurveyCenterline
+ SurveyHeader --"1"--> SurveyTeam
+ SurveyHeader --"1"--> SurveyInstrument
+ SurveyHeader --"0..*"--> SurveyExtra
+ SurveyStation --"1"--> SurveyFix
+ </div>
+</body>
+</html>
+
+<hr />
+Return to: <a href="trogarch.html">Troggle architecture</a><br />
+Return to: <a href="trogintro.html">Troggle intro</a><br />
+Troggle index:
+<a href="trogindex.html">Index of all troggle documents</a><br />
+
+<hr />
+</body>
+</html>
\ No newline at end of file