# Lat long Converter

## 1. Coordinate Picker Tools

- AMap Coordinate Picker: https://lbs.amap.com/tools/picker
- Baidu Coordinate Picker: https://api.map.baidu.com/lbsapi/getpoint/
- Tencent Coordinate Picker: https://lbs.qq.com/getPoint/
- Google Maps Coordinate Picker (Right-click): https://www.google.com/maps/

## 2. Supported Map Coordinate System Conversions

- Single coordinate conversion.
- Batch coordinate conversion, up to 100,000 entries.
- UTM to WGS84 or WGS84 to UTM uses 6-degree zones by default, 3-degree zones are not supported.

### 2.1 Seven Parameter Definition

The seven-parameter transformation is a common method used to convert coordinates between different geodetic datums. This model includes three translation parameters, three rotation parameters, and one scale parameter, making a total of seven parameters, hence the term 'seven parameters'.

2.1.1 Translation Parameters: - dx: Translation along the X-axis, measured in meters (m). - dy: Translation along the Y-axis, measured in meters (m). - dz: Translation along the Z-axis, measured in meters (m). 2.1.2 Rotation Parameters: - rx: Rotation around the X-axis, measured in radians (rad). Sometimes also measured in seconds, which need to be converted to radians. - ry: Rotation around the Y-axis, measured in radians (rad). - rz: Rotation around the Z-axis, measured in radians (rad). 2.1.3 Scale Parameter: - s: Scale factor, usually measured in parts per million (ppm). If the scale factor is 1 ppm, then the value of s is s = 1 * 10^-6. 2.1.4 Example： - dx:-679.0, dy:669.0, dz:-48.0, rx:-0.00000376632, ry:-0.00000094672, rz:-0.00000285841, s:0.0000000000

## 3. Introduction to Five Coordinate Systems

### 3.1 WGS84

WGS84 (World Geodetic System 1984) is the geodetic system and Earth reference framework used by the Global Positioning System (GPS). Developed by the U.S. Department of Defense, it is widely used in navigation, mapping, and Geographic Information Systems (GIS). Here are some key details about the WGS84 coordinate system:

3.1.1 Ellipsoid Parameters: - Semi-major axis (a): 6378137.0 meters - Inverse flattening (1/f): 298.257223563 - Semi-minor axis (b): 6356752.3142 meters 3.1.2 Origin: - The origin is at the Earth's center of mass, at the intersection of the equator and prime meridian. 3.1.3 Coordinate System: - Longitude: Measured east or west from the prime meridian, ranging from -180° to +180°. - Latitude: Measured north or south from the equator, ranging from -90° to +90°. - Elevation: Height relative to the ellipsoid surface.

### 3.2 GCJ02

GCJ-02 (Mars Coordinate System) is a geodetic system developed by the Chinese National Bureau of Surveying and Mapping, used for geospatial data within mainland China. Here are some key details about the GCJ-02 coordinate system:

3.2.1 Ellipsoid Parameters: - GCJ-02 uses the same ellipsoid parameters as WGS84, based on the Earth's ellipsoid model. 3.2.2 Offset Algorithm: - The GCJ-02 system applies encryption and offset processing to the WGS84 coordinates to ensure national geospatial data security. - The offset algorithm is confidential and not publicly disclosed, but various methods exist for conversion in development.

### 3.3 BD09

BD-09 (Baidu Coordinate System) is a geodetic system developed by Baidu, based on GCJ-02 (Mars Coordinate System) with further encryption and offset processing. It is widely used in Baidu Maps, Baidu Navigation, and other Baidu geospatial services. Here are some key details about the BD-09 coordinate system:

3.3.1 BD-09 Coordinate System: - BD-09 is derived from the GCJ-02 coordinate system through additional offset processing. - The system applies encryption algorithms to the original coordinates to protect geospatial data security. 3.3.2 Offset Algorithm: - The specific encryption algorithm of BD-09 is not publicly disclosed, but third-party implementations and reverse engineering results are available.

### 3.4 CGCS2000

CGCS2000 (China Geodetic Coordinate System 2000) is the national geodetic system of China, established by the National Administration of Surveying, Mapping and Geoinformation (NASG). It is widely used in national surveying, GIS, and navigation. Here are some key details about the CGCS2000 coordinate system:

3.4.1 Reference Ellipsoid Parameters: - Semi-major axis (a): 6378137.0 meters - Inverse flattening (1/f): 298.257222101 - Gravitational constant GM: 3.986004418×10^14 m^3s^-2 - Angular velocity ω: 7.292115×10^-5 rad s^-1 3.4.2 Origin: - The origin is at the Earth's center of mass, referenced to the International Terrestrial Reference Frame (ITRF). 3.4.3 Coordinate System: - Longitude: Measured east or west from the prime meridian, ranging from -180° to +180°. - Latitude: Measured north or south from the equator, ranging from -90° to +90°. - Elevation: Height relative to the ellipsoid surface.

### 3.5 UTM（Universal Transverse Mercator）

The UTM (Universal Transverse Mercator) coordinate system is a geographic coordinate system based on the transverse Mercator projection, dividing the Earth's surface into multiple projection zones, each covering 6 degrees of longitude. The UTM coordinate system uses meters to represent geographical locations.

3.5.1 Features of the UTM Coordinate System 3.5.1.1 Partitioning: - The Earth's surface is divided into 60 longitudinal zones, each 6 degrees of longitude wide. - Zone numbers start from 180 degrees west longitude, numbered from 1 to 60. - Each zone is further divided into the northern and southern hemispheres. 3.5.1.2 Coordinate Representation: - Easting: Measured in meters from the central meridian of the zone, with the central meridian's easting usually set to 500,000 meters to avoid negative values. - Northing: Measured in meters from the equator, northwards in the northern hemisphere and southwards in the southern hemisphere, with the equator's northing set to 10,000,000 meters in the southern hemisphere to avoid negative values. 3.5.2 UTM Coordinate Format 3.5.2.1 A typical UTM coordinate consists of the following parts: - Easting: Measured in meters from the central meridian of the zone. - Northing: Measured in meters from the equator. - Zone Number: Represents the range of longitude, from 1 to 60. - Zone Letter: Represents the range of latitude, from C to X (excluding I and O), with each letter zone covering 8 degrees of latitude. 3.5.2.2 Example: For example, here is a UTM coordinate: - Easting: 500,000 meters - Northing: 4,649,776 meters - Zone Number: 33 - Zone Letter: T

### 3.6 ETRS89

ETRS89 (European Terrestrial Reference System 1989) is a geodetic coordinate system for Europe, based on the 1989 resolution of the International Terrestrial Reference Frame (ITRF). ETRS89 is widely used across Europe, especially in mapping, cartography, and geographic information systems (GIS).

3.6.1 Features of ETRS89 - ETRS89 is based on the GRS80 ellipsoid and is synchronized with the International Terrestrial Reference System (ITRS) but fixed to the Eurasian plate, causing it to diverge over time from the ITRF (International Terrestrial Reference Frame). - It was defined to provide a consistent geodetic reference framework across Europe for cross-national GIS applications, environmental monitoring, and engineering surveys. 3.6.2 Ellipsoid Parameters - Semi-major axis (a): 6378137.0 meters - Flattening inverse (1/f): 298.257222101

### 3.7 JGD2011

JGD2011 (Japan Geodetic Datum 2011) is Japan's national geodetic coordinate system, based on the International Terrestrial Reference Frame 2005 (ITRF2005). JGD2011 was introduced to replace JGD2000 with the goal of improving measurement accuracy and addressing geographical coordinate changes caused by crustal movements, particularly the 2011 Great East Japan Earthquake.

3.7.1 Features of JGD2011 - JGD2011 was developed to address the impact of crustal movements and earthquakes on geodetic coordinates, particularly after the 2011 Great East Japan Earthquake. JGD2011 provides a more accurate geodetic reference. - JGD2011 is based on the GRS80 ellipsoid model, similar to JGD2000, referencing the International Terrestrial Reference Frame (ITRF) but updated to accommodate crustal changes. 3.7.2 Ellipsoid Parameters - Semi-major axis (a): 6378137.0 meters - Flattening inverse (1/f): 298.257222101

### 3.8 JGD2000

JGD2000 (Japan Geodetic Datum 2000) is Japan's national geodetic coordinate system introduced in 2002. It was established to replace the old Tokyo Datum and provide a more accurate geodetic reference suitable for modern mapping and geographic information systems (GIS).

3.8.1 Features of JGD2000 - JGD2000 is based on the International Terrestrial Reference Frame 1994 (ITRF94) and the Geodetic Reference System 1980 (GRS80) ellipsoid model. - Unlike the old Tokyo Datum, JGD2000 offers higher precision and consistency through the use of Global Positioning System (GPS) and modern surveying techniques. - JGD2000 became Japan's national geodetic coordinate system in 2000 and was officially implemented in 2002. It is widely used in surveying, GIS, engineering projects, and more. 3.8.2 Ellipsoid Parameters - Semi-major axis (a): 6378137.0 meters - Flattening inverse (1/f): 298.257222101

### 3.9 PRS92

PRS92 stands for Philippine Reference System 1992, which is the national geodetic coordinate system of the Philippines used for mapping, cartography, and geographic information systems (GIS). PRS92 is based on the WGS84 (World Geodetic System 1984) ellipsoid and was implemented to standardize and modernize the geographic positioning system of the Philippines.

3.9.1 Features of PRS92 - PRS92 is the national reference system of the Philippines, established by administrative order in 1992 to replace the old Luzon Datum 1911. - PRS92 is based on the WGS84 ellipsoid, resulting in minimal differences in geographical positioning compared to WGS84. - This coordinate system is widely used in land management, urban planning, engineering surveys, and environmental monitoring in the Philippines. 3.9.2 Ellipsoid Parameters - Semi-major axis (a): 6378137.0 meters (based on WGS84 ellipsoid) - Flattening inverse (1/f): 298.257223563

### 3.10 ED50

ED50 (European Datum 1950) is a geodetic coordinate system widely used in Europe during the mid-20th century. It was widely applied in mapping and surveying across European countries until more modern systems like ETRS89 gradually replaced it.

3.10.1 Features of ED50 - ED50 is based on the International Ellipsoid 1924 (also known as Hayford Ellipsoid), using the Krasovsky ellipsoid parameters. - The reference origin of this coordinate system is located at the Helmert Tower in Germany, making it widely used in Europe. - ED50 was used in most parts of Europe, but with the advent of Global Positioning System (GPS) and more modern systems like WGS84 and ETRS89, ED50 has gradually been replaced. 3.10.2 Ellipsoid Parameters - Semi-major axis (a): 6378388.0 meters - Flattening inverse (1/f): 297.0

### 3.11 HTRS96

HTRS96 (Croatian Terrestrial Reference System 1996) is the geodetic reference system used in Croatia. It is the national geodetic coordinate system of Croatia, based on the International Terrestrial Reference Frame 1996 (ITRF96) and the European Terrestrial Reference System 1989 (ETRS89). HTRS96 is widely used in surveying and geographic information systems (GIS) in Croatia.

3.11.1 Features of HTRS96 - HTRS96 is based on the ITRF96 and ETRS89 reference frameworks, using the GRS80 ellipsoid model. - HTRS96 serves as the standard reference coordinate system in Croatia, widely used in national surveying, cartography, and engineering projects. - HTRS96 and ETRS89 are very close in coordinates and can be used interchangeably in most cases. 3.11.2 Ellipsoid Parameters - Semi-major axis (a): 6378137.0 meters - Flattening inverse (1/f): 298.257222101

### 3.12 GDM2000

GDM2000 (Geodetic Datum of Malaysia 2000) is the geodetic coordinate system used in Malaysia. GDM2000 is based on the International Terrestrial Reference Frame 2000 (ITRF2000) and the GRS80 ellipsoid model. This coordinate system was introduced to replace the earlier Malayan Datum 1948 (MD48) to improve the accuracy and consistency of geographic data.

3.12.1 Features of GDM2000 - GDM2000 is Malaysia's national reference coordinate system, widely used in surveying, cartography, engineering projects, and geographic information systems (GIS). - The coordinate system is based on ITRF2000, using the GRS80 ellipsoid model, making it very close to the global standard WGS84. - GDM2000 provides higher measurement accuracy and accounts for crustal movement, ensuring the accuracy of geographic information. 3.12.2 Ellipsoid Parameters - Semi-major axis (a): 6378137.0 meters - Flattening inverse (1/f): 298.257222101

### 3.13 Clarke 1880

Clarke 1880 is a geodetic ellipsoid model defined by Alexander Ross Clarke in 1880. This ellipsoid model was the basis for mapping and surveying in many countries during the 19th and early 20th centuries, especially during the colonial period. Clarke 1880 ellipsoid has been adopted in various geographic coordinate systems, particularly in old surveying systems in Africa, South America, and the Indian subcontinent.

3.13.1 Features of Clarke 1880 - Clarke 1880 is a geodetic ellipsoid model providing an approximation of the Earth's shape for defining and converting geographic coordinates. - The model varies across different countries and regions, resulting in region-specific coordinate systems like Clarke 1880 (RGS), Clarke 1880 (IGN), etc. 3.13.2 Ellipsoid Parameters - Semi-major axis (a): 6,378,249.145 meters - Flattening inverse (1/f): 293.465

### 3.14 BJ54

BJ54 (Beijing 1954 Coordinate System) is a national geodetic reference coordinate system established by China in 1954. The BJ54 coordinate system is based on the Krasovsky 1940 ellipsoid, a model defined by the Soviet Union in 1940. BJ54 was widely used in surveying and mapping across mainland China, replacing earlier geographic datums.

3.14.1 Features of the BJ54 Coordinate System - Reference Ellipsoid: Krasovsky 1940 Ellipsoid - Datum Point: The origin of the BJ54 coordinate system is at Yongdingmen, Beijing. 3.14.2 Krasovsky 1940 Ellipsoid Parameters - Semi-major Axis (a): 6,378,245.0 meters - Inverse Flattening (1/f): 298.3 - Flattening (f): 1/298.3 ≈ 0.003352329869259135 - Semi-minor Axis (b): 6,356,863.019 meters - The semi-minor axis can be calculated using the formula b = a × (1 − f).

### 3.15 Indian 1975

Indian 1975 is a geographic coordinate system primarily used in Southeast Asia, especially in Thailand. It is based on the Krasovsky 1940 ellipsoid, a model introduced by the Soviet Union in 1940. The Indian 1975 coordinate system is widely used in Thailand's surveying and Geographic Information System (GIS).

3.15.1 Features of the Indian 1975 Coordinate System - Reference Ellipsoid: Krasovsky 1940 Ellipsoid - Datum Point: The datum point and origin are associated with the geodetic datum of the Indian subcontinent, but specific adjustments were made for use in the Southeast Asia region.

## 4. Latitude and Longitude Format Description

### 4.1 DMS (Degrees Minutes Seconds) Format

DMS format represents latitude and longitude in degrees, minutes, and seconds. For example: **Latitude: 40°26'46''N****Longitude: 79°58'56''W**

Here, 40° represents 40 degrees, 26' represents 26 minutes, and 46'' represents 46 seconds. The final character is the direction parameter, where longitude direction can be E (East) or W (West), and latitude direction can be N (North) or S (South).

DMS format is more suitable for use in paper maps or navigation.

### 4.2 Decimal Format

Decimal format represents latitude and longitude in decimal numbers. For example: **Latitude: 40.446****Longitude: -79.982**

Here, -79.982 represents the degrees of longitude, and 40.446 represents the degrees of latitude.

Decimal format is more suitable for use in computer and GIS systems.