Latitude & Longitude Coordinate Converter

Principles and Formulas

A GPS coordinate (116.4074, 39.9042) recorded by a smartphone in the field might appear hundreds of meters away when viewed on Baidu Maps. This discrepancy is caused by three mainstream coordinate systems. WGS84 is the internationally recognized standard for raw GPS coordinates. GCJ02 (commonly known as Mars Coordinates) is an encrypted coordinate system mandated by the Chinese National Administration of Surveying, Mapping and Geoinformation for use in electronic maps. BD09 is Baidu's proprietary coordinate system, which applies a secondary offset on top of GCJ02. There are no public linear formulas connecting them, but the industry has developed mature conversion algorithms through reverse engineering. Our calculator features this transformation logic, which has been verified by millions of developers. Simply select the source and target coordinate systems above, input the raw latitude and longitude, and you will instantly see the accurate position on the corresponding map on the right. A single conversion involves simultaneous offsets in both latitude and longitude, typically ranging from a few hundred meters to 1.5 kilometers. This is completely normal and not a calculation error.

How to Use

1. Open the "Latitude and Longitude Converter" page. You will see two dropdown menus: "Source Coordinate System" on the left and "Target Coordinate System" on the right.
2. In the left dropdown, select the origin of your current coordinates. For example, choose WGS84 for handheld GPS devices or native smartphone location data; choose GCJ02 for Amap (Gaode), Tencent Maps, or the domestic version of Apple Maps; choose BD09 for Baidu Maps coordinates.
3. In the right dropdown, select the map system you want to output to. For instance, if you want to plot a WGS84 coordinate on Baidu Maps, select BD09.
4. Paste your existing latitude and longitude numbers into the center input box in the format "longitude,latitude" (e.g., 116.4074,39.9042). Keeping 6 decimal places is sufficient for meter-level accuracy.
5. The converted coordinates will be displayed immediately below. You can also click the copy button next to it to copy the result and paste it directly into a map's search box for instant positioning.

Complete Example

Let's look at a real-world example. John collected a waypoint outdoors using a Garmin handheld GPS (WGS84 coordinate system): longitude 116.397428, latitude 39.909204. He wants to share this point on his team's shared Amap (Gaode Maps). Since Amap uses the GCJ02 coordinate system, he follows these steps:

• Select WGS84 in the "Source Coordinate System" dropdown.
• Select GCJ02 in the "Target Coordinate System" dropdown.
• Enter 116.397428,39.909204 into the coordinate input box.

The calculator instantly provides the result: the converted GCJ02 coordinate is 116.402516, 39.911437. The two coordinates might look very similar, but the actual physical distance has shifted by about 460 meters, moving from the east side of Tiananmen Square to near the Meridian Gate of the Forbidden City. This offset perfectly matches the random offset required by the GCJ02 national standard. By clicking the copy button on the right, John can paste this coordinate directly into the Amap app's search box, and the location will be perfectly accurate without any drift.

Typical Use Cases

• Outdoor Enthusiasts and Travelers: When returning from a trip with waypoints recorded offline via handheld GPS or smartphones, you may want to reconstruct your route on map apps like Amap or Baidu Maps. Convert your WGS84 coordinates here first before importing them into map tools; otherwise, your entire track might shift across the street or even to the next block.
• Content Creators and Real Estate Agents: You might receive a list of properties with coordinates, only to find their locations are off on Amap. This usually happens when raw Baidu coordinates are mixed into the data. You can use this converter to change BD09 to GCJ02 to correct the locations, ensuring you never go to the wrong place when viewing properties.
• Front-end and Map App Developers: When calling SDKs from different map providers—especially when displaying Amap and overlaying Baidu tiles on the same page—you must unify the coordinate systems first. During the development and debugging phase, this tool can quickly verify how specific coordinate points behave across different systems, saving you the hassle of writing trial-and-error code.

Common Mistakes and Pitfalls

1. Mixing up source and target coordinate systems: The most common error is treating Amap coordinates as WGS84 and converting them to Baidu, resulting in an even larger offset. Remember: your source coordinate system should always match the map where you originally obtained the coordinates.
2. Incorrect latitude and longitude order: Most tools require "longitude first, latitude second," which corresponds to the X and Y coordinate order. If you enter "39.9,116.4", your result might end up in Mongolia or the ocean. Before inputting, ensure the number before the comma is between ±180 (longitude) and the number after is between ±90 (latitude).
3. Confusing decimal places with accuracy: Entering 6 decimal places already provides an accuracy of about 0.1 meters; adding more decimals has no practical meaning for single-point conversions. However, if you only provide 2 decimal places, the deviation could be hundreds of meters. Don't mistake rough manual records for precise GPS data.
4. Assuming converted coordinates work on all maps: Coordinates converted to GCJ02 can be used directly on the domestic version of Apple Maps, Amap, and Tencent Maps, but not on Baidu Maps. Coordinates converted to BD09 can only be used within the Baidu ecosystem. You must perform a new conversion every time you switch map platforms.

Limitations and Considerations

This tool is built on publicly available GCJ02 and BD09 offset algorithms and is designed for coordinate processing within mainland China. Using GCJ02 or BD09 outside of mainland China has no practical purpose, as WGS84 is the direct standard for all international maps. Conversion accuracy can be affected by algorithm versions and map providers' backend policies. Generally, single-point deviation is within 10 meters. A few boundary areas (such as provincial borders or coastal mudflats) may experience an additional drift of over 30 meters due to stricter encryption policies. For rigorous applications such as surveying, cadastral mapping, or autonomous driving, please use officially released coordinate conversion parameters or apply for decryption keys through compliant channels. The results from this tool are intended for everyday positioning and development debugging reference only. Additionally, the calculation process runs entirely locally in your browser and does not upload your coordinates to any servers. However, if you are processing coordinates involving sensitive location data, we still recommend completing the operation in an offline environment and closing the page afterward.

Frequently Asked Questions (FAQ)

How do I determine which coordinate system my current coordinates use?
A practical method: paste the coordinates directly into the Amap search box. If the location points exactly to your intended spot, the coordinates are highly likely GCJ02. If it's off by several hundred meters, it's probably WGS84 or BD09. Next, try Baidu Maps. If the location is accurate there, it's BD09. By cross-verifying with these two maps, you can generally determine the coordinate system without needing to consult a manual.

Is it normal for the converted coordinates to still be off by a few dozen meters from the real location?
A single-point error within 10 to 30 meters is completely normal. If the deviation exceeds 50 meters, first check if your input order is longitude first, latitude second. Additionally, the raw positioning accuracy of a smartphone's GPS in environments like high-rise buildings, canyons, or indoors is only about 10 to a few dozen meters. This original error will carry over into the conversion result; it's not a flaw in the converter.

Can I convert multiple coordinates at once?
The current interface is designed for single-point conversions to facilitate quick queries and copying. If you have an entire list of coordinates that needs batch processing, we recommend using the batch conversion methods provided by various map SDKs, or looping through an open-source coordinate conversion library (like coordtransform) in a script. The results will match our algorithm.

What coordinate system does BeiDou positioning on smartphones use?
Just like GPS, the raw location output directly from BeiDou satellites uses the WGS84 coordinate system (strictly speaking, it's CGCS2000, but the two are considered equivalent for everyday accuracy). Therefore, whether it's GPS, BeiDou, or GLONASS, the native latitude and longitude output from devices should be treated as WGS84. To display them correctly on domestic Chinese maps, simply select WGS84 to GCJ02.

Will this tool leak my location data?
No. All calculations are performed entirely within your open browser page, and your coordinate data never leaves your device. However, if you are working with sensitive coordinates, it's always a good habit to regularly clear your clipboard and browser history.

Now you can try your own numbers in the calculator above to see exactly how much they differ across various maps.