The SAAScan has no way of knowing its position in the real world. Measurand’s SAAScan does not have magnetometers and cannot determine direction without an outside reference. To orient the data collected from the SAAScan to the real world, an azimuth offset angle must be measured from a known direction or marker on site to the physical X-mark on the instrument (which represents the positive X-axis direction in the data collected).
Determining the value for the azimuth offset is typically done manually with the included X-mark protractor (Option 2 below). However, if you have the flexibility to place your SAAScan reel such that the reel, and the segments coming off of the reel, are oriented with a desired reference marker or direction, then the SAARecorder software can automatically calculate an appropriate azimuth offset (Option 1 below). A third, hybrid method between automatic and manual azimuth offset determination is also presented that can be used should the X-marks not be easily identified on the SAAScan's segments (Option 3 below).
Option 1 - Automatic Azimuth Offset Determination
Azimuth offset can be determined automatically in the SAARecorder software if the SAAScan reel is properly aligned with the angle of the borehole or the desired direction of measurement (e.g. survey marker or magnetic North as measured with a compass).
Figure 1: Align the SAAScan reel with the desired direction of measurement - (A) side view, (B) top down view
Step 1 - Select a Horizontal Segment
Select a nearly horizontal segment coming off the reel and make note of its segment number. Segment number is determined by counting sensorized segments from the cable end of the SAAScan to the segment in question.
Step 2 - Connect to the ShapeArray with SAARecorder and Open Site Properties
Connect the ShapeArray to a computer and start SAARecorder. Open the Site Properties by selecting the SAA Setup | Site Properties menu option.
Figure 2: Select SAA Setup | Site Properties to open the Site Properties dialog
Step 3 - Use Determine Azimuth to Automatically Configure the Azimuth Offset
In the Site Properties window, click on the Determine Azimuth button. In the SAA Azimuth Determination window, enter the segment identified for the nearly horizontal segment (from step 1 above) in the SAA segment to use for determining azimuth field. Ensure that the Enter ‘A’ angle of SAA going into hole field is set to zero degrees.
Figure 3: A portion of the Azimuth Determination window in SAARecorder
SAARecorder calculates an appropriate azimuth offset to use in the SAA Azimuth field. The positive X-axis in the data recorded will be aligned with the direction to which the reel is aligned. Click OK to continue and note that the calculated azimuth offset value is automatically entered into the Azimuth Angle field. Click OK again to save the site properties.
Option 2 - Manually Measuring Azimuth Offset using the X-Mark and the Protractor
When it is not possible to position the SAAScan reel such that the segments coming off of the reel are aligned with the desired direction of measurement, then the azimuth offset will need to be measured manually using a protractor and the X-mark on the instrument. Each segment of an SAAScan has an X-mark scored into its surface. Azimuth offset can always be measured directly using the X-mark protractor and this marking.
Figure 4: X-Marks are scored into the surface of each segment of the SAAScan
Step 1 - Align Protractor Arrows with Desired Reference Direction
Place the square protractor on a near vertical segment coming out of the borehole. Orient the arrows on the square protractor so that they point in the desired direction of measurement.
Step 2 - Measure Azimuth Offset with Clear Plastic Disk
Place the clear plastic disk over the square protractor and align the X-Line with the scored X-mark in the near vertical segment. Record the highlighted azimuth offset value.
Figure 5: Point arrows to desired direction and then align the X-line on clear plastic with X-mark
Step 3 - Connect to the ShapeArray with SAARecorder and Configure Site Properties
Connect the ShapeArray to a computer and start SAARecorder. Open the Site Properties by selecting the SAA Setup | Site Properties menu option. In the Site Properties window, enter the recorded azimuth offset value (from step 2) into the Azimuth Offset Angle field and click OK.
Option 3 - Measuring Alignment with the X-mark Protractor
When the X-marks on the SAAScan are not easily identified, then the X-mark protractor can be still to be used to properly determine the azimuth offset if the SAAScan reel can be oriented with the desired direction of measurement. This method uses a nearly vertical segment at the top of the borehole as a reference segment and a nearly horizontal segment on the reel for determining the azimuth offset, as shown in the figure below.
Figure 6: The suggested configuration for determining initial azimuth – (left) side view, (right) top view
Step 1 - Align Protractor Arrows with Desired Reference Direction
With the ShapeArray secured to a stable base, place the square protractor around the nearly vertical segment located near the top of the borehole. Align the arrows on the square protractor with the desired reference direction. For example, a survey marker on site, magnetic north as measured by compass, or the angle of the borehole is often used as the reference direction.
Step 2 - Select a Horizontal Segment
Select a nearly horizontal segment coming off the reel and make note of its segment number. Segment number is determined by counting sensorized segments from the cable end of the SAAScan to the segment in question.
Step 3 - Measure Azimuth Offset with Clear Plastic Disk
Place the clear plastic disk over the square protractor. Draw an imaginary line through the center of the nearly horizontal segment (selected in step 2 above) down to the protractor. Rotate the clear plastic disk until the X-line is aligned with the center line of the nearly horizontal segment. Record the azimuth offset value highlighted on the square protractor.
Step 4 - Connect to the ShapeArray with SAARecorder and Open Site Properties
Connect the ShapeArray to a computer and start SAARecorder. Open the Site Properties by selecting the SAA Setup | Site Properties menu option.
Step 5 - Use Determine Azimuth to Configure the Azimuth Offset
In the Site Properties window, click on the Determine Azimuth Offset button. In the SAA Azimuth Determination window, enter the segment identified for the nearly horizontal segment (from step 2) in the SAA segment to use for determining azimuth field. In the Enter ‘A’ angle of SAA going into hole field, enter the previously determined azimuth value (from step 3). (see figure 3 above)
SAARecorder calculates an appropriate azimuth offset to use in the SAA Azimuth Offset field. The positive X-axis in the data recorded will be aligned with the direction to which the reel is aligned. Click OK to continue and note that the calculated azimuth value is automatically entered into the Azimuth Offset Angle field. Click OK again to save the site properties.