Land Survey Standards Purged of Colonial Legacy After 105 Years

Gyeonggi Province announced on the 23rd that it will convert cadastral records created using the Tokyo Datum to the World Geodetic System, an international standard.

A geodetic datum expresses a specific location on Earth as coordinates. Since 1910 during the Japanese colonial period, South Korea has used the Tokyo Datum—a system designed to fit Japanese geography—as the standard for land surveying.

At that time, Japan established a survey system for the purpose of rapidly implementing its land survey project. Rather than installing independent survey reference points in Korea, Japan connected them to the Tokyo Prime Meridian, establishing primary triangulation bases at Geoje Island and Yeolryeong Island in Busan through Tsushima Island, and linked these with approximately 600 triangulation points to create the survey system.

The cadastral records created this way have been maintained for over 100 years.

As a result, the coordinates of Korea's territory are offset 365 meters to the northwest based on the World Geodetic System. This has reduced compatibility with topographic maps, nautical charts, and military maps that have already been converted to the World Geodetic System, creating limitations in their integrated and composite use.

The World Geodetic System, meanwhile, is an international standard positioning reference. Adopting it would enable real-time utilization of GNSS (Global Navigation Satellite System) precision position information in land surveying, and reduce error margins to approximately 3 centimeters, which is expected to contribute to protecting property rights for residents.

The World Geodetic System conversion project, undertaken to mark the 70th anniversary of liberation, will not use actual surveying methods. Instead, it will calculate various differences between the Tokyo Datum and World Geodetic System through specialized programs, then apply the calculated conversion coefficients to current cadastral maps and forest maps.

In this regard, the province jointly conducted World Geodetic System conversion on the 20th, with approximately 70 people including civil servants and surveyors gathering in one place.

The province plans to conduct field verification and other checks by December and complete the project this year.

Additionally, the province will continue to promote theoretical education and communication with municipal and county officials to successfully advance the World Geodetic System conversion project, which will be pursued incrementally through 2020.

Since the geodetic system conversion will proceed technically, officials must accurately understand the principles of conversion to prevent inaccurate results from being produced.

The province also plans to annually produce a "World Geodetic System Conversion White Paper" to meticulously document the contents of the conversion project and to serve as reference material by comparing and analyzing performance before and after conversion in the future.

Yu Byeong-chan, director of the Land Information Division of Gyeonggi Province, said, "The World Geodetic System conversion has great significance in recovering land sovereignty through the settlement of colonial legacy, and we expect it to serve as a driving force for the development of the spatial information industry."