Abstract: A down hole surveying tool (10) is for directional surveying of boreholes. The tool (10) includes a body (11) which accommodates a composite sensor device (17). The sensor device (17) is supported for rotation about an indexing axis (4) in a rotary mount (31) which provides an indexing platform (33). The sensor device (17) can be indexed about the indexing axis between two indexing positions which are 180 degrees apart. An indexing mechanism (70) is provided for selectively indexing the sensor device (17) about the indexing axis (4). The sensor device (17) includes a two-axis gyroscope (13) and a two-axis accelerometer (15) connected together and rotatable in unison. The indexing axis (4) is perpendicular to the two sensitive axes of the gyroscope (13) and the two sensitive axes of the accelerometer (15). The gyroscope (13) and accelerometer (15) are rigidly fixed with respect to each other to provide a sensor package which constitutes the composite sensor device (17).

Abstract: A down hole surveying tool (10) is for directional surveying of boreholes. The tool (10) includes a body (11) which accommodates a two-axis gyroscope (13) and a two-axis accelerometer (15). The gyroscope (13) and accelerometer (15) are rigidly fixed with respect to each other to provide a composite sensor device (17). The sensor device (17) is supported in a rotary mount (31) for rotation about an indexing axis (4). The sensor device (17) can be indexed about the indexing axis between two indexing positions which are 180 degrees apart. An indexing mechanism (70) is provided for selectively indexing the sensor device (17) about the indexing axis (4). The indexing mechanism (70) includes a drive portion (71) and a driven portion (72) adapted for selective interaction to impart indexing motion to the sensor device (17). The driven portion (72) is movable into and out of engagement with the drive portion (71) upon rotation of the rotary mount (31) about a pitch axis (1) using a pitch drive mechanism (51).

Abstract: A core sample orientation system (10) comprising a first portion (11) and a second portion (12). The first portion (11) comprises a downhole unit adapted to be connected to a core tube of a core drill, and the second portion (12) comprises a control unit. The downhole unit (11) is adapted for cooperation with a core tube for recording data relating to the orientation of the core tube, and the control unit (12) is adapted to cooperate with the downhole unit to receive and process orientation data from the downhole unit and provide an indication of the orientation of a core sample within the core tube at a time prior to separation of the core sample from the underground environment from which it was obtained. The downhole unit (11) is configured to cooperate with the control unit (12) to establish an operative connection therebetween.

Abstract: A housing (15) for connection to a downhole assembly (17), the housing comprising first and second sections (31, 32), the first section (31) being adapted for connection to a portion of the downhole assembly, the second section (32) defining a compartment (23) to receive a downhole tool (11) or component thereof, the second section (32) being configured to provide a path (40) for fluid flow past the compartment (23) as the assembly descends within the borehole, and the first section (31) being configured for fluid communication between a passage in said portion of the downhole assembly and the fluid flow path (40).