From f02c2c44524599f077f9cceec0341376a78ef0bc Mon Sep 17 00:00:00 2001
From: Philip Sargent <philip.sargent@gmail.com>
Date: Sun, 21 Sep 2025 18:11:34 +0100
Subject: [PATCH] explanation of namespace for QM 'comment' lines - online edit
 of handbook/survey/qmentry.html

---
 handbook/survey/qmentry.html | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/handbook/survey/qmentry.html b/handbook/survey/qmentry.html
index 2e728d350..b2d5ba651 100644
--- a/handbook/survey/qmentry.html
+++ b/handbook/survey/qmentry.html
@@ -158,6 +158,11 @@ and then
 </ol>
 
 <p>If the new QM is explored but is not worth surveying (e.g. a snow-filled drop which in a later year is seen to be just a pile of snow), then edit the original survex file to repeat the same survey station as the "resolution station" and put a comment with the <em>date</em> this was done and a reference to the logbook entry or wallet.
+  
+<h4>Subtle point</h4>
+<p>The QM line is in the <em>survex namespace</em> of the cave survex data, e.g. within the 
+  *begin 161/*end 161 survex namespace block for cave 161, but not within any named survex block which contains survey data. This is why you have to include the name of the survex block, e.g. "surveyname" in "surveyname.5" above, in your definition of a QM. 
+  <p>A subtle side effect is that the line defining the QM can be put into <em>any</em> of the survex files for that cave. This has occasionally been done by accident by new expoers [2025], but it seems to work fine.
 
 <!--<p>In 2022 we had a proposal  (which was coded into troggle) to add an extra line to the original survex file, now that survex files can be edited 
 easily on-line (and the version control happens invisibly and automatically):