From af794b05982bcf0b4023abff781aa6f07fceb399 Mon Sep 17 00:00:00 2001
From: Thomas Kolb <cfr34k-git@tkolb.de>
Date: Sat, 29 May 2021 21:26:59 +0200
Subject: [PATCH] Generate azimuth lines and basic Maidenhead locator grid
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No text in the grid „squares“ yet.
---
 qsomap.py | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 83 insertions(+), 6 deletions(-)

diff --git a/qsomap.py b/qsomap.py
index 5a94b14..de05838 100755
--- a/qsomap.py
+++ b/qsomap.py
@@ -180,10 +180,7 @@ for k, v in simplegeodata.items():
 
     v['proj_coordinates'] = proj_polys
 
-#print(simplegeodata['AW']['proj_coordinates'])
-###print(simplegeodata['DE']['proj_coordinates'])
 
-#debug plot
 # generate the SVG
 
 doc = svgwrite.Drawing("/tmp/test.svg", size=(2*R, 2*R))
@@ -191,7 +188,26 @@ doc = svgwrite.Drawing("/tmp/test.svg", size=(2*R, 2*R))
 doc.defs.add(doc.style("""
         .country {
             stroke: black;
-            stroke-width: 0.01;
+            stroke-width: 0.01px;
+        }
+
+        .dist_circle_label, .azimuth_line_label {
+            font-size: 3px;
+            font: sans-serif;
+            text-anchor: middle;
+        }
+
+        .dist_circle, .azimuth_line {
+            fill: none;
+            stroke: black;
+            stroke-width: 0.1px;
+        }
+
+        .maidenhead_line {
+            fill: none;
+            stroke: red;
+            stroke-width: 0.1px;
+            opacity: 0.5;
         }
 """))
 
@@ -223,8 +239,69 @@ d_max = 40075/2
 for distance in [500, 1000, 2000, 3000, 4000, 5000, 6000, 8000, 10000, 12000,
                  14000, 16000, 18000, 20000]:
     r = R * distance / d_max
-    doc.add(doc.circle(center=(R, R), r=r, fill='none',
-                       stroke_width=0.1, stroke='black'))
+    doc.add(doc.circle(center=(R, R), r=r,
+                       **{'class': 'dist_circle'}))
+
+    doc.add(doc.text(f"{distance} km", (R, R-r+5),
+            **{'class': 'dist_circle_label'}))
+
+# generate azimuth lines in 30° steps
+
+for azimuth in np.arange(0, np.pi, np.pi/6):
+    start_x = R + R * np.cos(azimuth-np.pi/2)
+    start_y = R + R * np.sin(azimuth-np.pi/2)
+    end_x = R - R * np.cos(azimuth-np.pi/2)
+    end_y = R - R * np.sin(azimuth-np.pi/2)
+
+    doc.add(doc.line((start_x, start_y), (end_x, end_y),
+            **{'class': 'azimuth_line'}))
+
+    azimuth_deg = int(np.round(azimuth * 180 / np.pi))
+    textpos = (2*R - 10, R - 2)
+
+    txt = doc.text(f"{azimuth_deg:d} °", textpos,
+                   **{'class': 'azimuth_line_label'})
+    txt.rotate(azimuth_deg - 90, center=(R, R))
+    doc.add(txt)
+
+    txt = doc.text(f"{azimuth_deg+180:d} °", textpos,
+                   **{'class': 'azimuth_line_label'})
+    txt.rotate(azimuth_deg - 90 + 180, center=(R, R))
+    doc.add(txt)
+
+# generate Maidenhead locator grid (first two letters only)
+
+group = doc.g()
+
+N = 18  # subdivisions of Earth
+resolution = 4096
+
+for x in range(0, N):
+    lon = x * 2 * np.pi / N
+    lat = np.linspace(-np.pi/2, np.pi/2, resolution)
+
+    x, y = map_azimuthal_equidistant(lat, lon, ref_lat, ref_lon, R)
+    points = np.array([x, y]).T + R
+
+    group.add(doc.polyline(points, **{'class': 'maidenhead_line'}))
+
+for y in range(0, N):
+    lon = np.linspace(-np.pi, np.pi, resolution)
+    lat = y * np.pi / N - np.pi/2
+
+    x, y = map_azimuthal_equidistant(lat, lon, ref_lat, ref_lon, R)
+    points = np.array([x, y]).T + R
+
+    group.add(doc.polyline(points, **{'class': 'maidenhead_line'}))
+
+doc.add(group)
+
+"""
+for x in range(0, 26):
+    for y in range(0, 26):
+        sectorname = chr(ord('A')+x) + chr(ord('A')+y)
+"""
+
 
 print(f"Saving {doc.filename}…")
 doc.save(pretty=True)