app.py

import streamlit as st
import folium
from streamlit_folium import folium_static
import requests
import json
import geopandas as gpd

st.set_page_config(page_title="No Fly Zones Map", layout="wide")

@st.cache_data
def fetch_data():
    url = "https://esua.cad.gov.hk/web/droneMap/getData"
    try:
        response = requests.get(url)
        response.raise_for_status()
        return response.json()  # Directly parse JSON response
    except requests.RequestException as e:
        st.error(f"Error fetching data: {e}")
        return None


def parse_json_data(json_data):
    geojson_list = []

    try:
        # Extract the list of GeoJSON features from the JSON data
        rfz_features = json_data.get('data', {}).get('rfzFeatures', [])
        for feature_str in rfz_features:
            try:
                geojson = json.loads(feature_str)  # Parse the GeoJSON string
                geojson_list.append(geojson)
            except json.JSONDecodeError as e:
                st.warning(f"Could not parse GeoJSON from feature: {feature_str[:100]}... Error: {e}")

    except Exception as e:
        st.error(f"Error processing JSON data: {e}")

    return geojson_list


def main():
    st.subheader("Restricted Flying Zones (“RFZ”) from Civil Aviation Department")
    # Fetch data
    with st.spinner("Fetching data..."):
        json_data = fetch_data()

    if json_data:
        geojson_list = parse_json_data(json_data)

        if geojson_list:
            m = folium.Map(location=[22.3193, 114.1694], zoom_start=11,
                       tiles='https://landsd.azure-api.net/dev/osm/xyz/basemap/gs/WGS84/tile/{z}/{x}/{y}.png?key=f4d3e21d4fc14954a1d5930d4dde3809',
                       attr="Map information from Lands Department")

            folium.TileLayer(
                tiles='https://mapapi.geodata.gov.hk/gs/api/v1.0.0/xyz/label/hk/en/wgs84/{z}/{x}/{y}.png',
                attr="Map Map information from Lands Department"
            ).add_to(m)

            for geojson in geojson_list:
                gdf = gpd.GeoDataFrame.from_features(geojson['features'])

                # Set the CRS to EPSG:4326 (WGS 84)
                gdf.set_crs(epsg=4326, inplace=True)

                folium.GeoJson(
                    gdf,
                    tooltip=folium.GeoJsonTooltip(fields=['name'], aliases=['Name'], localize=True)
                ).add_to(m)

            folium_static(m, width=1500, height=800)
        else:
            st.error("No valid GeoJSON data found in the response.")
    else:
        st.error("Failed to fetch data. Please try again later.")
    st.write("Restricted Flying Zones (“RFZ”) reflected in this drone map are designated by the Small Unmanned Aircraft Order (Cap. 448G). In connection to other restricted areas/ zones under other legislation or regulation such as the Air Navigation (Flight Prohibition) Order (Cap. 448E), users should refer to other maps for information.")

if __name__ == "__main__":
    main()