Finding Azimuth Offset of an SAAV from the X-mark
SAAV azimuth offset can be measured and input in to the ShapeArray software during data processing. This way the ShapeArray data is displayed so that the X direction corresponds to the expected direction of movement or other desired heading.
WARNING: Alignment of a ShapeArray's X-mark should never be adjusted by lifting and rotating the ShapeArray.
To determine the azimuth offset of an SAAV, use the instructions given below.
ShapeArray X-mark Protractor
SAAVs are delivered with an SAAV X-mark Protractor to measure azimuth offset for data processing. The X-mark Protractor is used to determine alignment in cases where the ShapeArray is completely placed inside the borehole. For ShapeArrays with one or more magnetometers, it is typically not necessary to use the SAA X-mark Protractor, as the readings are automatically adjusted so that +X corresponds to magnetic North. For ShapeArrays with one or more magnetometers, the protractor would only be required if some direction reference (other than magnetic North) were desired.
Step 1 - Place the Square Protractor
Place the square protractor around the Fiberglass Extension Tube at the top of the SAAV. Rotate the square protractor until the arrows are pointed to one of the following:
- The expected direction of movement
- Other desired heading of the ShapeArray
- Other job site datum
Figure 1: The square protractor placed around the Fiberglass Extension Tube at the top of the ShapeArray
If the protractor needs to be placed over the PVC casing rather than the Fiberglass Extension Tube, the required hole size is marked so it can be cut to fit.
Step 2 - Place and Align the Clear Disk
Place the clear disk marker with the X-Line around the Fiberglass Extension Tube and on top of the square protractor so that the X-Line is aligned with X-Mark on the Fiberglass Extension Tube. Note: the X-line, the X-Mark on the Springbox assembly, and the X-mark on the Fiberglass Extension Tube should now all be aligned.
Figure 2: The clear disk (in grey) on the ShapeArray and the square protractor. The X-Line on the protractor and the X-Mark on the Fiberglass Extension Tube are aligned with each other
Step 3 - Read the Angle
Make note of the angle at the X-Line. This will be directly used in the software when specifying the azimuth offset angle of the ShapeArray. For more information, you can refer to the following documentation:
- SAARecorder manual, section SAA Setup | Site Properties
- SAAView manual, section Azi and Aza
- SAACR_raw2data manual, section Configure Conversion Settings
NOTE: Attached to this article are printable versions of the X-Mark Protractor dial and wheel. The wheel portion of the protractor is designed to be printed on clear, transparent plastic.