From 411b5f73ee9570fcefbf7ebc9c51871b485fe00a Mon Sep 17 00:00:00 2001 From: Esteban82 Date: Wed, 28 Oct 2026 19:30:17 -0300 Subject: [PATCH] Rewrite the plot -A documentation Explain how geographic points are connected: without -A along the shorter great circle arc (antipodal points cause an error), with -A by straight lines on the map that depend on -R and -J and are not split at the map edges. Also fix the 'gragraphic' typo. Co-Authored-By: Claude Opus 5.5 --- doc/rst/source/explain_line_draw.rst_ | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/doc/rst/source/explain_line_draw.rst_ b/doc/rst/source/explain_line_draw.rst_ index 0a507c034c5..bdb8fe7ce6f 100644 --- a/doc/rst/source/explain_line_draw.rst_ +++ b/doc/rst/source/explain_line_draw.rst_ @@ -1,16 +1,26 @@ **-A**\ [**x**\|\ **y**] - By default, geographic line segments are drawn as great circle arcs by resampling - coarse input data along such arcs. To disable this sampling and draw them as - straight lines, use the |-A| flag. For Cartesian data, points are simply connected. - To adjust these behaviors, append a directive: + Control how consecutive geographic points are connected: - - **x** - First follow *x*, then *y* for staircase curves. - - **y** - First follow *y*, then *x* for staircase curves. + - Without |-A|, two points are joined along the shorter great circle arc (e.g., from + longitude 0 to 181 the line passes through the western hemisphere). To follow the + longer arc instead, add an intermediate point on that side. Antipodal points have no + unique great circle and cause an error. + - With |-A|, the points are joined by straight lines on the map, as in a Cartesian + plot, so the result depends on the map projection and region (e.g., rhumb lines on a + Mercator map). These lines are not split at the map edges, so for data that cross the + east or west edge of a global map (e.g., tracks across the Dateline) either omit |-A|, + center the map on the data, or split the data at that edge. + + For Cartesian data, points are simply connected by straight lines. For either kind of + data, append a directive to draw staircase curves instead: + + - **x** - First follow *x*, then *y*. + - **y** - First follow *y*, then *x*. Here, *x* and *y* have the following meanings: - For Cartesian projections, *x* and *y* are the X- and Y-axis. - - For gragraphic projections, *x* and *y* are parallels and meridians. + - For geographic projections, *x* and *y* are parallels and meridians. - For polar projections, *x* and *y* are theta and radius. When used together with |-S|\ **v** (Cartesian vectors), the **x** and **y**