BD09MC to BD09 Converter

Convert BD09MC (Baidu Mercator) planar coordinates back to BD09 geographic coordinates.

Coordinate Conversion

BD09MC (BD09MC X / Y (meters))

BD09 (BD09 Longitude / Latitude)

Enter coordinates and click Convert

Map View

Compare BD09MC (source) and BD09 (target) positions side by side. Maps are synchronized — pan or zoom on either map to compare.

Loading map...

About BD09MC and BD09

This tool converts coordinates from the BD09MC coordinate system to the BD09 coordinate system. The conversion uses the standard mathematical transformation algorithms widely adopted in GIS and mapping applications.

Default example (Tiananmen Square)

BD09MC: 12944200, 4848447

BD09: Click Convert

Quick Facts

✓Sub-meter accuracy
✓Round-trip precision: 1 meter
✓Web Mercator extent (±20037508m)
✓API access available

API Usage

Python

import requests

response = requests.post(
    "https://www.geocoordconv.cc.cd/api/convert",
    json={
        "lng": 116.397428,
        "lat": 39.909204,
        "from": "BD09MC",
        "to": "BD09"
    }
)
result = response.json()
print(f"Converted: {result['data']['lng']}, {result['data']['lat']}")

JavaScript

const response = await fetch("https://www.geocoordconv.cc.cd/api/convert", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    lng: 116.397428,
    lat: 39.909204,
    from: "BD09MC",
    to: "BD09"
  })
});
const result = await response.json();
console.log(`Converted: ${result.data.lng}, ${result.data.lat}`);

cURL

curl -X POST https://www.geocoordconv.cc.cd/api/convert \
  -H "Content-Type: application/json" \
  -d '{"lng": 116.397428, "lat": 39.909204, "from": "BD09MC", "to": "BD09"}'

Frequently Asked Questions

How accurate is this conversion?

The conversion achieves sub-meter accuracy for coordinates within China. Round-trip conversion (BD09MC → BD09 → BD09MC) maintains precision within 1e-6 degrees (approximately 0.1 meters at mid-latitudes).

What if my coordinates are outside China?

The BD09MC → BD09 transformation is designed for coordinates within China (73°E–135°E, 18°N–54°N). For coordinates outside this region, the tool will display an "Outside China" warning. The GCJ02 and BD09 offsets are only applied within Chinese territory.

Can I use this tool programmatically?

Yes. Send a POST request to /api/convert with JSON body containing lng, lat, from, and to fields. See code examples above for Python, JavaScript, and cURL.

What are BD09MC and BD09 coordinates?

BD09MC and BD09 are geographic coordinate systems used in mapping and GIS applications. Each system uses longitude (east-west) and latitude (north-south) measured in decimal degrees. The conversion between them applies specific mathematical offsets defined by their respective standards.