Publish Date: 1994 Author Name: Tony Waltham The information on the rock mass obtained by this method was very limited. Recently a Swedish company (Hagconsult) has introduced an improvement. Their technique involves lowering a miniature television camera into the hole and examining the rock quality and other properties of the rock… Your download is ready. It should start automatically within a few seconds. If it doesn't, click here to download the requsted file.