BEIJING, Oct. 26 (Xinhua) -- A 500-year-old question -- Just how long is the great wall? -- will be answered in 2008 by two Chinese government departments.

A massive geographical survey of the Great Wall will be launched by China's State Administration of Cultural Heritage (SACH) and State Bureau of Surveying and Mapping (SBSM).

The survey will be completed by 2007 and the basic statistics of the Great Wall, including its length and layout, will be released in 2008, officials said.

Local governments have been gathering statistics on the Great Wall since the 1980's. "But due to limited knowledge and technology at the time, most parts of the Great Wall remain unknown to us, " Shan Qixiang, director of the SACH said.

"It's necessary for the government to organize a scientific survey so we have a comprehensive and accurate understanding of the Great Wall," Shan said.

The wall is generally considered to start at the Jiayuguan Passin Gansu Province and stretch 6,000 km to the Shanhaiguan Pass on the shores of Bohai Bay in the east, yet no one knows for sure the ancient wonder's exact length.

The departments will jointly establish a database based on the results of their survey to facilitate future research and protection of the Great Wall.

The survey has already started in the Hebei and Henan provinces.

Scientists and historians say they will focus their work on the portion of the Great Wall near Beijing, which was built during the Ming Dynasty (1368-1644).

The Great Wall was first built in the Warring States Period (475-221 BC), when separate sections were built in various strategic areas to defend China against invasion by northern nomadic tribes.

As nature and human activity continue to take their toll on the Great Wall, the Chinese government has increased efforts to protect the unique historical relic.

On Tuesday, the Chinese government issued a regulation to protect the Great Wall. The regulation bans defacing and driving on the Great Wall, taking soil or bricks and building anything on it that is not designed to protect it.