Menggunakan data spasial dengan mssql-python

Microsoft SQL menyediakan dua jenis data spasial yang dapat Anda gunakan melalui driver mssql-python. Pilih jenis berdasarkan apa yang diwakili oleh koordinat Anda:

Jenis	Deskripsi	Skenario penggunaan
geography	Sistem koordinat bumi bulat	Koordinat GPS, peta, apa pun di permukaan bumi. Jaraknya dalam meter. SRID 4326 (WGS 84) adalah standar untuk GPS.
geometry	Sistem koordinat bidang datar	Denah lantai, gambar CAD, dunia game, atau sistem koordinat Cartesian apa pun. Jarak berada dalam satuan sistem koordinat Anda.

Sisipkan data spasial

Gunakan fungsi konstruktor Microsoft SQL seperti geography::Point() atau berikan string Well-Known Text (WKT).

Data geografis (titik)

Sisipkan titik geografis menggunakan konstruktor titik dengan lintang, bujur, dan SRID.

import mssql_python

connection_string = "Server=<server>.database.windows.net;Database=AdventureWorks2022;Authentication=ActiveDirectoryDefault;Encrypt=yes"

conn = mssql_python.connect(connection_string)
cursor = conn.cursor()

# Insert a geographic point (longitude, latitude)
# Note: Microsoft SQL uses (longitude, latitude) order
cursor.execute("CREATE TABLE #Locations (Name NVARCHAR(100), GeoLocation GEOGRAPHY)")
cursor.execute("""
    INSERT INTO #Locations (Name, GeoLocation)
    VALUES (%(name)s, geography::Point(%(lat)s, %(lon)s, 4326))
""", {"name": "Seattle", "lat": 47.6062, "lon": -122.3321})
conn.commit()

Geografi dari WKT (Well-Known Text)

Sisipkan data geografis menggunakan format Teks Well-Known, yang mendukung titik, string baris, dan poligon.

# Well-Known Text format
wkt_point = "POINT(-122.3321 47.6062)"
wkt_line = "LINESTRING(-122.3321 47.6062, -122.4194 37.7749)"
wkt_polygon = "POLYGON((-122.40 47.60, -122.30 47.60, -122.30 47.65, -122.40 47.65, -122.40 47.60))"

cursor.execute("DROP TABLE IF EXISTS #Locations")
cursor.execute("CREATE TABLE #Locations (Name NVARCHAR(100), GeoLocation GEOGRAPHY)")
cursor.execute("""
    INSERT INTO #Locations (Name, GeoLocation)
    VALUES (%(name)s, geography::STGeomFromText(%(wkt)s, 4326))
""", {"name": "Route", "wkt": wkt_line})
conn.commit()

Data geometri

Sisipkan data geometri bidang datar menggunakan titik dan poligon untuk gambar CAD atau denah lantai.

# Insert a geometry point (flat coordinate system)
cursor.execute("CREATE TABLE #FloorPlan (RoomName NVARCHAR(100), RoomShape GEOMETRY)")
cursor.execute("""
    INSERT INTO #FloorPlan (RoomName, RoomShape)
    VALUES (%(name)s, geometry::Point(%(x)s, %(y)s, 0))
""", {"name": "Office 101", "x": 50.0, "y": 100.0})

# Insert a geometry polygon
room_wkt = "POLYGON((0 0, 0 10, 20 10, 20 0, 0 0))"
cursor.execute("""
    INSERT INTO #FloorPlan (RoomName, RoomShape)
    VALUES (%(name)s, geometry::STGeomFromText(%(wkt)s, 0))
""", {"name": "Conference Room", "wkt": room_wkt})
conn.commit()

Mengkueri data spasial

Gunakan metode spasial seperti STAsText() dan properti Lat/Long untuk mengambil koordinat dalam format yang dapat dibaca.

Ambil sebagai teks

Ambil koordinat spasial sebagai format Teks Well-Known bersama dengan properti lintang dan bujur.

cursor.execute("""
    SELECT 
        City,
        SpatialLocation.STAsText() AS LocationWKT,
        SpatialLocation.Lat AS Latitude,
        SpatialLocation.Long AS Longitude
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL
""")

for row in cursor.fetchall()[:5]:
    print(f"{row.City}: {row.Latitude}, {row.Longitude}")
    print(f"  WKT: {row.LocationWKT}")

Ambil sebagai GeoJSON

Microsoft SQL mendukung konversi GeoJSON. Di SQL Server 2017+, Anda dapat menggunakan fungsi string untuk membangun GeoJSON secara langsung, atau mengonversi dalam Python seperti yang ditunjukkan di bawah ini:

cursor.execute("""
    SELECT 
        City,
        SpatialLocation.STAsText() AS WKT
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL AND City = %(city)s
""", {"city": "Seattle"})

for row in cursor:
    print(f"{row.City}: {row.WKT}")

Temukan titik terdekat

Temukan semua lokasi dalam jarak tertentu dari titik referensi menggunakan fungsi jarak spasial.

# Find locations within 10 km of Seattle
cursor.execute("""
    DECLARE @seattle geography = geography::Point(47.6062, -122.3321, 4326);
    
    SELECT 
        City,
        SpatialLocation.STDistance(@seattle) / 1000 AS DistanceKM
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL
      AND SpatialLocation.STDistance(@seattle) < 50000  -- 50 km in meters
    ORDER BY SpatialLocation.STDistance(@seattle)
""")

for row in cursor.fetchall()[:5]:
    print(f"{row.City}: {row.DistanceKM:.2f} km away")

Temukan titik dalam poligon

Temukan semua titik yang berpotongan dengan atau termasuk dalam wilayah poligon geografis.

# Find all addresses within a region
cursor.execute("""
    DECLARE @region geography = geography::STPolyFromText(
        'POLYGON((-122.5 47.5, -122.2 47.5, -122.2 47.7, -122.5 47.7, -122.5 47.5))',
        4326
    );
    
    SELECT City, SpatialLocation.STAsText() AS Location
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL
      AND @region.STIntersects(SpatialLocation) = 1
""")

Hitung jarak

Metode Microsoft SQL STDistance() mengembalikan jarak dalam meter untuk jenis geografi.

Jarak antara dua titik

Buat fungsi pembantu untuk menghitung jarak dalam kilometer antara dua titik geografis.

def get_distance_km(cursor, point1: tuple, point2: tuple) -> float:
    """Calculate distance between two points in kilometers."""
    cursor.execute("""
        DECLARE @point1 geography = geography::Point(%(lat1)s, %(lon1)s, 4326);
        DECLARE @point2 geography = geography::Point(%(lat2)s, %(lon2)s, 4326);
        SELECT @point1.STDistance(@point2) / 1000 AS DistanceKM;
    """, {
        "lat1": point1[0], "lon1": point1[1],
        "lat2": point2[0], "lon2": point2[1]
    })
    return cursor.fetchval()

# Seattle to San Francisco
distance = get_distance_km(cursor, (47.6062, -122.3321), (37.7749, -122.4194))
print(f"Distance: {distance:.2f} km")

Hitung luas

Hitung luas wilayah geografis dalam kilometer persegi.

cursor.execute("""
    DECLARE @region geography = geography::STPolyFromText(
        'POLYGON((-122.5 47.5, -122.2 47.5, -122.2 47.7, -122.5 47.7, -122.5 47.5))',
        4326
    );
    SELECT 
        'Seattle Region' AS Name,
        @region.STArea() / 1000000 AS AreaSqKm
""")

row = cursor.fetchone()
print(f"{row.Name}: {row.AreaSqKm:.2f} sq km")

Operasi spasial

Microsoft SQL mendukung operasi himpunan pada objek spasial, termasuk gabungan, interseksi, dan buffer.

Penyatuan bentuk

Gabungkan dua poligon geografis menjadi satu bentuk dan hitung luas total.

cursor.execute("""
    DECLARE @parcel1 geography = geography::STPolyFromText(
        'POLYGON((-122.35 47.60, -122.33 47.60, -122.33 47.62, -122.35 47.62, -122.35 47.60))',
        4326
    );
    DECLARE @parcel2 geography = geography::STPolyFromText(
        'POLYGON((-122.34 47.61, -122.32 47.61, -122.32 47.63, -122.34 47.63, -122.34 47.61))',
        4326
    );
    DECLARE @combined geography = @parcel1.STUnion(@parcel2);
    
    SELECT @combined.STAsText() AS CombinedWKT,
           @combined.STArea() / 1000000 AS TotalAreaKM
""")

row = cursor.fetchone()
print(f"Combined area: {row.TotalAreaKM:.2f} sq km")

Persimpangan

Temukan area yang tumpang tindih di mana dua wilayah geografis berpotongan.

polygon1_wkt = "POLYGON((-122.35 47.60, -122.33 47.60, -122.33 47.62, -122.35 47.62, -122.35 47.60))"
polygon2_wkt = "POLYGON((-122.34 47.61, -122.32 47.61, -122.32 47.63, -122.34 47.63, -122.34 47.61))"

cursor.execute("""
    DECLARE @region1 geography = geography::STPolyFromText(%(wkt1)s, 4326);
    DECLARE @region2 geography = geography::STPolyFromText(%(wkt2)s, 4326);
    
    SELECT 
        @region1.STIntersection(@region2).STAsText() AS IntersectionWKT,
        @region1.STIntersection(@region2).STArea() / 1000000 AS AreaKM
""", {"wkt1": polygon1_wkt, "wkt2": polygon2_wkt})

Buffer (perluas area)

Buat zona penyangga di sekitar titik geografis dan temukan semua lokasi dalam radius penyangga.

# Find all addresses within 5km buffer of a point
cursor.execute("""
    DECLARE @center geography = geography::Point(47.6062, -122.3321, 4326);
    DECLARE @buffer geography = @center.STBuffer(5000);  -- 5 km buffer
    
    SELECT City
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL
      AND @buffer.STIntersects(SpatialLocation) = 1
""")

Integrasi Python

Ambil string WKT dari Microsoft SQL dan uraikan dengan pustaka Shapely untuk pemrosesan geometri sisi klien.

Dengan perpustakaan Shapely

Instal dengan menjalankan pip install shapely.

from shapely import wkt
from shapely.geometry import Point, Polygon

# Retrieve spatial data from Person.Address
cursor.execute("""
    SELECT City, SpatialLocation.STAsText() AS WKT
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL AND City IN ('Seattle', 'Redmond')
""")

for row in cursor:
    # Parse WKT into Shapely geometry
    geom = wkt.loads(row.WKT)
    
    if isinstance(geom, Point):
        print(f"{row.City}: Point at ({geom.x}, {geom.y})")
    elif isinstance(geom, Polygon):
        print(f"{row.City}: Polygon with area {geom.area}")

Membuat data spasial dengan Shapely

Buat objek geometris menggunakan pustaka Shapely dan konversikan ke format WKT untuk disisipkan ke Microsoft SQL.

from shapely.geometry import Point, Polygon, LineString
from shapely import wkt

# Create geometries in Python
seattle = Point(-122.3321, 47.6062)
seattle_wkt = wkt.dumps(seattle)

route = LineString([(-122.3321, 47.6062), (-122.4194, 37.7749)])
route_wkt = wkt.dumps(route)

# Insert into a temp table
cursor.execute("CREATE TABLE #Routes (Name NVARCHAR(100), Path NVARCHAR(MAX))")
cursor.execute("""
    INSERT INTO #Routes (Name, Path)
    VALUES (%(name)s, %(wkt)s)
""", {"name": "Seattle to SF", "wkt": route_wkt})

cursor.execute("SELECT Name, Path FROM #Routes")
row = cursor.fetchone()
print(f"{row.Name}: {row.Path[:40]}...")

Konversi ke GeoJSON

Konversi data spasial dari format WKT ke GeoJSON untuk aplikasi berbasis web dan layanan pemetaan.

import json
from shapely import wkt
from shapely.geometry import mapping

cursor.execute("""
    SELECT City, SpatialLocation.STAsText() AS WKT
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL AND City = 'Seattle'
""")

row = cursor.fetchone()
geom = wkt.loads(row.WKT)

geojson = {
    "type": "Feature",
    "properties": {"name": row.City},
    "geometry": mapping(geom)
}

print(json.dumps(geojson, indent=2))

Integrasi GeoDataFrame

Muat data spasial dari Microsoft SQL ke GeoDataFrame GeoPandas untuk analisis geospasial tingkat lanjut.

import geopandas as gpd
from shapely import wkt
import pandas as pd

cursor.execute("""
    SELECT AddressID, City, SpatialLocation.STAsText() AS WKT
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL AND City = 'Seattle'
""")

# Build DataFrame
rows = cursor.fetchall()
df = pd.DataFrame(
    [(r.AddressID, r.City, r.WKT) for r in rows],
    columns=['id', 'city', 'wkt']
)

# Convert to GeoDataFrame
df['geometry'] = df['wkt'].apply(wkt.loads)
gdf = gpd.GeoDataFrame(df, geometry='geometry', crs="EPSG:4326")

# Now use GeoPandas operations
print(gdf.head())

Indeks spasial

Buat indeks spasial di Microsoft SQL untuk mempercepat kueri pada himpunan data spasial besar.

-- Geography index on Person.Address
CREATE SPATIAL INDEX SIX_Address_SpatialLocation
ON Person.Address(SpatialLocation)
USING GEOGRAPHY_GRID
WITH (
    GRIDS = (LEVEL_1 = MEDIUM, LEVEL_2 = MEDIUM, LEVEL_3 = MEDIUM, LEVEL_4 = MEDIUM),
    CELLS_PER_OBJECT = 16
);

-- Geometry index (example with custom table)
CREATE SPATIAL INDEX SIX_FloorPlan_RoomShape
ON dbo.FloorPlan(RoomShape)
USING GEOMETRY_GRID
WITH (
    BOUNDING_BOX = (0, 0, 1000, 1000),
    GRIDS = (LEVEL_1 = HIGH, LEVEL_2 = HIGH, LEVEL_3 = HIGH, LEVEL_4 = HIGH)
);

Tips kinerja

Terapkan teknik ini untuk menjaga kueri spasial tetap efisien dalam skala besar.

Gunakan petunjuk indeks spasial

Gunakan indeks spasial untuk mempercepat kueri pada himpunan data spasial besar.

cursor.execute("""
    DECLARE @region geography = geography::STPolyFromText(
        'POLYGON((-122.5 47.5, -122.2 47.5, -122.2 47.7, -122.5 47.7, -122.5 47.5))',
        4326
    );

    SELECT City
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL
      AND SpatialLocation.STIntersects(@region) = 1
""")

Filter terlebih dahulu, lalu hitung

Optimalkan kueri spasial dengan terlebih dahulu menerapkan filter kotak pembatas cepat, lalu melakukan perhitungan jarak yang tepat.

# Approximate filter with bounding box, then precise calculation
cursor.execute("""
    DECLARE @center geography = geography::Point(47.6062, -122.3321, 4326);
    
    SELECT City, SpatialLocation.STDistance(@center) AS Distance
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL
      AND SpatialLocation.Filter(@center.STBuffer(10000)) = 1  -- Fast bounding box filter
      AND SpatialLocation.STDistance(@center) < 10000         -- Precise distance check
    ORDER BY Distance
""")

Kurangi presisi untuk tampilan

Sederhanakan geometri spasial untuk tampilan dengan mengurangi presisi koordinat.

cursor.execute("""
    SELECT 
        City,
        SpatialLocation.Reduce(100).STAsText() AS SimplifiedWKT  -- 100 meter tolerance
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL AND City = 'Seattle'
""")

Sistem referensi koordinat

SRID menentukan sistem koordinat dan memengaruhi cara Microsoft SQL menghitung jarak dan area.

Nilai SRID umum

SRID (Pengidentifikasi Referensi Spasial) mendefinisikan sistem koordinat untuk data Anda. Menggunakan SRID yang salah menghasilkan perhitungan jarak dan area yang salah.

SRID	Nama	Skenario penggunaan
4326	WGS 84	Koordinat GPS, pemetaan berbasis web
4269	NAD 83	Survei Amerika Utara
0	Tidak ada SRID	Geometri datar, koordinat lokal

Mengonversi antar SRID

Ambil data spasial dan periksa SRID-nya untuk memverifikasi sistem koordinat.

cursor.execute("""
    -- Geography is always round-earth, but SRID defines datum
    SELECT SpatialLocation.STAsText() AS WKT,
           SpatialLocation.STSrid AS SRID
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL
""")

Praktik terbaik

Terapkan panduan ini untuk bekerja dengan data spasial dengan benar dan efisien.

Memvalidasi geometri

Periksa validitas data spasial dan identifikasi masalah geometris sebelum diproses.

cursor.execute("""
    SELECT 
        City,
        SpatialLocation.STIsValid() AS IsValid,
        SpatialLocation.IsValidDetailed() AS InvalidReason
    FROM Person.Address
    WHERE SpatialLocation IS NOT NULL
      AND SpatialLocation.STIsValid() = 0
""")

for row in cursor:
    print(f"Invalid: {row.City} - {row.InvalidReason}")

Jadikan geometri valid

Gunakan metode MakeValid() ini untuk secara otomatis memperbaiki bentuk geometris yang tidak valid.

# Example with a temp table
cursor.execute("""
    CREATE TABLE #SpatialFix (Name NVARCHAR(100), GeoLocation GEOGRAPHY);
    INSERT INTO #SpatialFix VALUES ('Test', geography::STGeomFromText('POLYGON((0 0, 0 1, 1 0, 0 0))', 4326));
    UPDATE #SpatialFix
    SET GeoLocation = GeoLocation.MakeValid()
    WHERE GeoLocation.STIsValid() = 0
""")

Pilih jenis yang tepat

Pilihan antara geography dan geometry menentukan bagaimana Microsoft SQL menghitung jarak dan area:

• geografi: Lokasi dunia nyata (titik GPS), perhitungan permukaan bumi, jarak dalam meter.
• geometri: Permukaan datar (denah lantai, CAD), sistem koordinat Cartesian, atau ketika SRID tidak masalah.

Konten terkait

• Pemetaan jenis data
• Dokumentasi spasial Microsoft SQL