From 07dc0b55a08b41327d5644daec8a7066cea14b54 Mon Sep 17 00:00:00 2001
From: marvin <marvin@nubo.sh>
Date: Fri, 18 Sep 2026 00:32:02 +0200
Subject: [PATCH] =?UTF-8?q?Mask=20out=20Skytteh=C3=B8j=20and=20everything?=
 =?UTF-8?q?=20south=20of=20it=20(lat=2055.628)?=
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Add south_bound_lat to modes.yaml and a load_south_bound() helper in
prepare.py. When set, the area geometry is intersected with the north
half-plane above the cutoff, so all downstream clipping (lines, stops,
stations) cascades automatically.

Removed: 94 bus stops (including Skyttehøj), 1 station (Vestamager),
and line segments south of the boundary (Metro M1 tail, buses 32-36).
---
 copenhagen/config/modes.yaml  |  5 +++++
 copenhagen/scripts/prepare.py | 16 ++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/copenhagen/config/modes.yaml b/copenhagen/config/modes.yaml
index 00151b8..b076eca 100644
--- a/copenhagen/config/modes.yaml
+++ b/copenhagen/config/modes.yaml
@@ -30,6 +30,11 @@ exclude:
   - agency: Snälltåget AB
     ref: "083"
 
+# South bound: drop every stop/station south of this latitude (inclusive),
+# and clip transit lines at this boundary. Used to cut the map short of
+# Skyttehøj (Amager Landevej) and everything south of it on Amager.
+south_bound_lat: 55.628
+
 modes:
   metro:
     agencies: [Metroselskabet]
diff --git a/copenhagen/scripts/prepare.py b/copenhagen/scripts/prepare.py
index ef03532..cf4d267 100644
--- a/copenhagen/scripts/prepare.py
+++ b/copenhagen/scripts/prepare.py
@@ -30,6 +30,7 @@ import sys
 import geopandas as gpd
 import pandas as pd
 import yaml
+from shapely.geometry import box
 
 from _common import CONFIG, GTFS_RAW, PROCESSED
 
@@ -69,6 +70,15 @@ def load_bus_whitelist():
     }
 
 
+def load_south_bound():
+    """South latitude cutoff from modes.yaml, or None.
+
+    When set, stops/stations south of (and transit lines below) this
+    latitude are dropped. Used to trim the map at a boundary.
+    """
+    return _load_modes_yaml().get("south_bound_lat")
+
+
 def _load_modes_yaml():
     return yaml.safe_load((CONFIG / "modes.yaml").read_text())
 
@@ -331,6 +341,12 @@ def main():
     styling = load_styling()
     area_geom = load_area()
 
+    south_bound = load_south_bound()
+    if south_bound is not None:
+        north = box(-180, south_bound, 180, 90)
+        area_geom = area_geom.intersection(north)
+        print(f"south bound: clipping area at lat {south_bound}", flush=True)
+
     routes = load_routes(modes, load_exclude())
 
     bus_wl = load_bus_whitelist()