operations_computation.rst: add note about proj_create_crs_to_crs not necessarily using the operation that appears as first

1 files changed, 15 insertions, 3 deletions

diff --git a/docs/source/operations/operations_computation.rst b/docs/source/operations/operations_computation.rst
index 0bc57ff0..5c2596e6 100644
--- a/docs/source/operations/operations_computation.rst
+++ b/docs/source/operations/operations_computation.rst
@@ -59,9 +59,9 @@ From a code point of view, the entry point of the algorithm is the C++
 
 It combines several strategies:
 
-- look up in the PROJ database for available operations
-- consider the pair (source CRS, target CRS) to synthetize operations depending
-  on the nature of the source and target CRS.
+  - look up in the PROJ database for available operations
+  - consider the pair (source CRS, target CRS) to synthetize operations depending
+    on the nature of the source and target CRS.
 
 Geographic CRS to Geographic CRS, with known identifiers
 --------------------------------------------------------
@@ -156,6 +156,18 @@ performed in the order they are listed below:
     lexicographic order (e.g. "FOO to BAR (3)" will have higher precedence than
     "FOO to BAR (2)")
 
+.. note::
+
+    :c:func:`proj_trans`, on the results returned by :c:func:`proj_create_crs_to_crs`,
+    will not necessarily use the operation that
+    is listed in first position due to the above algorithm. :c:func:`proj_trans`
+    has more context, since it has the coordinate to transform, so it can compare
+    this coordinate to the area of use of operations. Typically, the above criteria
+    will favor an operation that has a larger area of use over another one with a
+    smaller area, due to it being more generally applicable. But once coordinates are known,
+    :c:func:`proj_trans` can select an operation with a smaller
+    area of use that applies to the coordinate to transform.
+
 Geodetic/geographic CRS to Geodetic/geographic CRS, without known identifiers
 -----------------------------------------------------------------------------