🗺️ Map Chiang Mai with Python · ทำแผนที่เชียงใหม่ด้วย Python · 用 Python 画清迈地图

0 Get ready · เตรียมตัว · 做好准备

pip3 install folium

mkdir ~/Documents/Code/maps
cd ~/Documents/Code/maps
vim chiang_mai_map.py

1 The entry point · จุดเริ่มต้นของโปรแกรม · 程序的入口

def main():
    print("Making a map of Chiang Mai...")


if __name__ == "__main__":
    main()

2 Two numbers find any place on earth · ตัวเลขสองตัวชี้ตำแหน่งได้ทั้งโลก · 两个数字就能找到地球上任何地方

# lat, lon  —  always in this order
CENTRE = (18.7883, 98.9853)          # the middle of the old city

#   18.7883,   98.9853   Chiang Mai   -> north of the equator, east
#   39.9057,  116.3913   Beijing      -> further east, so a bigger number
#   39.7419, -105.0710   Casa Bonita  -> MINUS means west of the zero line

3 Make the map · สร้างแผนที่ · 生成地图

from pathlib import Path

import folium

CENTRE = (18.7883, 98.9853)
OUT_FILE = Path(__file__).resolve().parent / "chiang_mai_map.html"


def main():
    the_map = folium.Map(location=CENTRE, zoom_start=13, tiles="OpenStreetMap")
    the_map.save(str(OUT_FILE))
    print(f"Saved: {OUT_FILE}")


if __name__ == "__main__":
    main()

4 Your first pin · หมุดแรกของคุณ · 你的第一个图钉

    folium.Marker(
        location=[18.78776, 98.99327],
        tooltip="Tha Phae Gate",
        popup="The east gate of the old city",
    ).add_to(the_map)

5 A class for a place · สร้างคลาสสำหรับสถานที่ · 给地点写一个类

COLOURS = {
    "temple": "purple",
    "market": "orange",
    "travel": "blue",
    "landmark": "red",
    "school": "green",
    "nature": "darkgreen",
}
ICONS = {
    "temple": "place-of-worship",
    "market": "cart-shopping",
    "travel": "plane",
    "landmark": "landmark",
    "school": "graduation-cap",
    "nature": "tree",
}


class Place:
    def __init__(self, name, thai, lat, lon, kind, note):
        self.name = name        # English name
        self.thai = thai        # Thai name
        self.lat = lat          # how far north
        self.lon = lon          # how far east
        self.kind = kind        # "temple", "market", "travel", ...
        self.note = note        # one line for the popup

    def colour(self):
        return COLOURS.get(self.kind, "gray")

    def icon(self):
        return ICONS.get(self.kind, "circle-info")

    def popup(self):
        return f"<b>{self.name}</b><br>{self.thai}<br><i>{self.note}</i>"

    def add_to(self, the_map):
        folium.Marker(
            location=[self.lat, self.lon],
            popup=folium.Popup(self.popup(), max_width=260),
            tooltip=self.name,
            icon=folium.Icon(color=self.colour(), icon=self.icon(), prefix="fa"),
        ).add_to(the_map)

6 Fourteen places, one loop · สิบสี่สถานที่ ลูปเดียว · 十四个地点，一个循环

PLACES = [
    Place("Wat Phra That Doi Suthep", "วัดพระธาตุดอยสุเทพ", 18.80501, 98.92218,
          "temple", "On the mountain. 306 steps to the top."),
    Place("Wat Phra Singh", "วัดพระสิงห์", 18.78821, 98.98138,
          "temple", "The biggest temple inside the old city."),
    Place("Wat Chedi Luang", "วัดเจดีย์หลวง", 18.78714, 98.98678,
          "temple", "A huge old chedi, broken by an earthquake."),
    Place("Wat Don Chan", "วัดดอนจั่น", 18.76021, 99.03257,
          "temple", "Temple and school for children in Tha Sala."),
    Place("Tha Phae Gate", "ประตูท่าแพ", 18.78776, 98.99327,
          "landmark", "The east gate of the old city wall."),
    Place("Three Kings Monument", "อนุสาวรีย์สามกษัตริย์", 18.79023, 98.98735,
          "landmark", "The three kings who founded the city in 1296."),
    Place("Warorot Market", "ตลาดวโรรส", 18.79024, 99.00053,
          "market", "Big day market. Food, cloth, everything."),
    # ... eight more in the finished file ...
]

# Two places nowhere near Chiang Mai. Same class, no changes needed.
FAR_AWAY = [
    Place("Casa Bonita", "คาซาโบนิต้า", 39.74194, -105.07103,
          "far", "A very large Mexican restaurant in Lakewood, Colorado."),
    Place("Beijing", "ปักกิ่ง", 39.90571, 116.39130,
          "far", "The capital of China. Almost the same latitude as Casa Bonita."),
]

    for place in PLACES:
        place.add_to(the_map)

    for place in FAR_AWAY:
        place.add_to(the_map)

7 Draw a shape — the old city · วาดรูปทรง — เมืองเก่า · 画一个形状 —— 古城

# The four corners of the old city moat. These are close, not exact.
OLD_CITY = [
    (18.7949, 98.9791),      # north west
    (18.7949, 98.9933),      # north east
    (18.7807, 98.9933),      # south east
    (18.7807, 98.9791),      # south west
]


def add_old_city(the_map):
    folium.Polygon(
        locations=OLD_CITY,
        color="#b03030",
        weight=3,
        fill=True,
        fill_opacity=0.08,
        popup="The old city moat (roughly)",
    ).add_to(the_map)

8 How far is it, really? · ไกลแค่ไหนกันแน่ · 到底有多远？

import math


def distance_km(a, b):
    """How far apart are two places, in kilometres?"""
    radius = 6371.0                     # the earth, in km
    lat1, lon1, lat2, lon2 = map(math.radians, [a.lat, a.lon, b.lat, b.lon])
    d_lat = lat2 - lat1
    d_lon = lon2 - lon1
    h = math.sin(d_lat / 2) ** 2 + math.cos(lat1) * math.cos(lat2) * math.sin(d_lon / 2) ** 2
    return 2 * radius * math.asin(math.sqrt(h))

def find(name):
    """Get one place out of the list by its name."""
    for place in PLACES:
        if place.name == name:
            return place
    return None

9 A line and a circle · เส้นและวงกลม · 一条线和一个圆

def add_temple_walk(the_map):
    stops = ["Wat Phra Singh", "Wat Chedi Luang", "Tha Phae Gate"]
    points = [(find(name).lat, find(name).lon) for name in stops]

    folium.PolyLine(
        locations=points,
        color="#1e6660",
        weight=5,
        opacity=0.8,
        tooltip="A short temple walk",
    ).add_to(the_map)

    total = 0.0
    for first, second in zip(stops, stops[1:]):
        total += distance_km(find(first), find(second))
    return total


def add_airport_circle(the_map):
    airport = find("Chiang Mai Airport")
    folium.Circle(
        location=[airport.lat, airport.lon],
        radius=5000,                       # metres
        color="#2a6cb0",
        weight=2,
        fill=True,
        fill_opacity=0.06,
        popup="5 km from the airport",
    ).add_to(the_map)

10 Two map styles · สลับสไตล์แผนที่ · 两种地图样式

    folium.TileLayer("CartoDB positron", name="Plain", show=False).add_to(the_map)

    folium.LayerControl().add_to(the_map)

11 The whole program · โปรแกรมทั้งหมด · 完整的程序

cd ~/Documents/Code/maps
python3 chiang_mai_map.py

Put 14 places on the map.
The temple walk is 1.3 km.
Doi Suthep is 7.7 km from Tha Phae Gate
  ...but that is the straight line. The road up the mountain is much longer.

12 Now change it · ลองแก้ดู · 现在动手改它