Communications Research Laboratory will host an international workshop named GEMSTONE (International workshop on GEodetic Measurements by the colocation of Space Techniques ON Earth) which is sponsored by the Science and Technology Agency in Japan in January of 1999.

Importance of colocation between the space techniques has been stressed. Although we had limited number of colocated stations in the past, the situation is changing. We can study systematic errors which may be invisible by a single technique, through the colocation. From a colocation, we may understand the behavior of the atmosphere and other physical effects. These study will lead us the reference frame improvement. On the other hand, we have to solve the technical problems such as ground surveying. This workshop will focus a topic of colocation in the aspects of the technical points and its contribution to the geodesy and astrometry. More information will appear on Web Site http://ksp.nict.go.jp.