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Publication Number: FHWA-HRT-08-056
Date: November 2008

LTPP Manual for Profile Measurements and Processing

CHAPTER 3. PROFILE MEASUREMENTS USING THE FACE DIPSTICK®

3.1 INTRODUCTION

The Dipstick® , which is manufactured by Face Company, is a manually operated device for collection of precision profile measurements, and can collect data at rates greater than traditional rod and level survey procedures. However, the profile obtained from Dipstick® measurements may have a vertical shift from the true profile because of systematic cumulative errors in the Dipstick® readings. The body of the Dipstick® houses an inclinometer (pendulum), LCD panels, and a battery for power supply. The Dipstick® sensor is mounted in such a way that its axis and line passing through the footpad contact points are co-planar. The sensor becomes unbalanced as the Dipstick® is pivoted from one leg to the other as it is moved down the pavement, causing the display to become blank. After the sensor achieves equilibrium, the difference in elevation between the two points is displayed. Swivel footpads having an approximate diameter of 32 mm should be used for all measurements.

Each RSC is in possession of at least one manual Dipstick® (Model 1500) and two automated Dipsticks® (Model 2000 and Model 2200). Both the manual and the automated Dipsticks® display data in millimeters. The spacing between the two feet of the Dipstick® is approximately 304.8 mm for both models. When the automated Dipstick® is used for data collection, it should be used in manual mode, with data recorded manually.

Profile measurements on GPS and SPS sites that cannot be obtained using the LTPP profiler should be obtained using the Dipstick® . Decisions with respect to the need for Dipstick® measurements at these test sections should be made on a case-by-case basis by responsible RSC personnel.

3.2 OPERATIONAL GUIDELINES

3.2.1 General Procedures

Dipstick® measurements are to be taken by personnel who have been trained in using the device and are familiar with the procedures described in this manual. Data collection using the Dipstick® is a two person operation, with one person operating the Dipstick® and the other person recording the data. However, a single person can collect the data if that person uses a voice activated tape recorder to record the readings.

Detailed scheduling and traffic control at test sites must be coordinated by the RSC. Traffic control at test sites will be provided by either the State highway agency (in the United States ) or provincial highway agency (in Canada ). Layout of the site should not be undertaken until all applicable traffic control equipment and devices are in place.

3.2.2 LTPP Procedures

3.2.2.1 Maintenance of Records:

The operator is responsible for forwarding all data collected during testing (see forms in appendix D). In addition, the operator is also required to forward other records related to Dipstick® operation, which are described in section 3.6, to the RSC.

3.2.2.2 Equipment Repairs:

RSCs are responsible for ensuring that LTPP owned equipment is properly maintained. Decisions required for proper maintenance and repair should be made based on the testing schedule and expedited as necessary to prevent disruption of testing.

3.2.2.3 Accidents:

In event of an accident, the operator will inform the RSC of the incident as soon as practical after the mishap. Details of the event shall subsequently be reported in writing to the RSC.

3.2.3 Footpad Spacing of Dipstick ®

Field studies performed with Dipsticks® have indicated that the actual spacing between the centerline of the two footpads is not exactly 304.8 mm. Testing has shown that the footpad spacing for the various Dipsticks® used by the RSCs can vary between 304.280 and 306.176 mm.

RSCs are required to determine the footpad spacing of all Dipsticks® in their possession annually using the procedures described in appendix E. The RSC should maintain a log documenting the test date and the computed footpad spacing for each Dipstick® .

Note: The RSCs performed the test specified in appendix E in December 2003, and should know the footpad spacing of each Dipstick® in their possession. For RSCs that do not routinely perform longitudinal Dipstick® measurements, it is acceptable to perform this test annually only on the Dipstick® that has the footpad spacing closest to 304.8 mm. If during this test, the offset at the end of the section is not within ±25 mm of the offset obtained from the previous year's test, the procedure described in appendix E should be used to obtain the footpad spacing of all Dipsticks® operated by the RSC.

When performing longitudinal Dipstick® measurements, the RSCs should select the Dipstick® in their possession that has a footpad spacing that is closest to 304.8 mm.

3.3 FIELD TESTING

3.3.1 General Background

The following sequence of fieldwork tasks and requirements provides an overall perspective of the typical workday at a test section:

  1. Task 1: Personnel Coordination.
    1. Dipstick® crew (operator and recorder).
    2.  
    3. Traffic control crew supplied by highway agency or traffic control contractor working for the highway agency.
    4.  
    5. Other LTPP, State or Provincial highway agency, and RSC personnel (they are observers and are not required to be present).
    6.  
  2.  
  3. Task 2: Site Inspection.
    1. Assess general pavement condition (within test section limits).
    2.  
    3. Identify wheel paths (when performing longitudinal measurements).
    4.  
  4.  
  5. Task 3: Dipstick® Measurements.
    1. Mark wheel paths (when performing longitudinal measurements).
    2.  
    3. Perform operational checks on the Dipstick® .
    4.  
    5. Obtain Dipstick® measurements.
    6.  
    7. Quality control (includes post data collection check and closure error computations (see 3.3.3)).
    8.  
  6.  
  7. Task 4: Form Completion.
    1. Complete forms DS-1 through DS-7 (see appendix D) for longitudinal profile measurements.
    2.  
    3. Complete form DS-7 and DS-8 (see appendix D) for transverse profile measurements.
    4.  
  8.  

On arrival at a site, the operator will carefully plan activities to be conducted to insure the most efficient utilization of time. While many activities can only be accomplished by the operator and/or recorder, it may be necessary to enlist the assistance of other personnel at the site to mark wheel paths. In general, arrangements for this assistance should be made in advance by the RSC.

Assuming that a manual distress survey is also to be performed at the site, traffic control typically should be available for six to eight hours. This should provide adequate time for Dipstick® measurements in both wheel paths, as well as for the manual distress survey, to be completed. Experienced Dipstick® operators can obtain approximately 500 readings per hour.

Collecting profile data is the primary responsibility of the operator. In order to ensure that data collected in the four LTPP regions are identical in format, certain guidelines and standards have been established for data acquisition and handling.

3.3.2 Site Inspection and Layout—Longitudinal Profile Measurements

The pavement must be clear of ice, snow, and puddles of water before profile measurements can be taken with the Dipstick® , as such conditions can affect profile measurements. Pools of water can cause the feet of the Dipstick® to get wet, resulting in a potential for slippage and can also possibly damage electronics in the Dipstick® .

The longitudinal Dipstick® measurement procedure consists of performing an elevation survey in each wheel path, and using transverse measurements at the section ends to form a closed loop. As illustrated in figure 93 , measurements start at Station 0+00 in the right wheel path and proceed in the direction of traffic toward the end of the section. At end of the section, transverse measurements are made to the end point of the survey line in the left wheel path. A 0.61-m diameter closure circle around this point is used to close transverse measurements on this start location for measurements in the left wheel path. Longitudinal measurements are then performed in the left wheel path back to Station 0+00. Transverse measurements and the closure circle are used to close the survey on the starting point. This procedure is designed for a 152.4-m test section; however, the concept can be applied to test sections of any length.

Figure 93. Illustration. Site layout and measurement procedure for measuring longitudinal profiles with the Dipstick . This figure shows the layout at a site for performing longitudinal Dipstick  measurements. Two longitudinal survey lines are established on the pavement along the left and the right wheel paths, with the distance to each survey line from the centerline of the lane being 0.826 m. The end of the section is located 152.4 m from the start of the section. Transverse lines are placed connecting the left and the right wheel paths at the start and the end of the section. A 0.305-m closure circle is marked at the intersection of the survey line along the left wheel path and the transverse line at the end of the section. A similar closure circle is marked at the intersection of the survey line along the right wheel path and the transverse line at the start of the section.
Figure 93. Illustration. Site layout and measurement procedure for measuring longitudinal profiles with the Dipstick®.

If acceptable conditions are present to perform the Dipstick® measurements, clean both wheel paths of loose stones and debris to prevent slippage of the Dipstick® footpads during measurements. The first step in the site layout is to locate the wheel paths, where each wheel path is located at a distance of 0.826 m from the center of the travel lane. Use following procedure to locate center of travel lane:

Once center of travel lane has been identified, use following procedure to layout the site:

  1. Establish a transverse chalk line to define the beginning of the test section if this location is not marked with a stripe. Dipstick® measurements along the right wheel path will begin with the back edge of the Dipstick® footpad located immediately adjacent to leave edge of white stripe at the beginning of the monitoring portion of the test section. At a 16 mm offset (radius of footpad of Dipstick® ) in front of the leave edge of the white stripe at the beginning of the section (or in front of the transverse line that was marked if the white stripe was missing), use a chalk line to mark a transverse line parallel to the start line of the section. This transverse line is considered to be Station 0+00. Identify the location of two longitudinal elevation survey lines 0.826 m from the center of the lane. Mark these locations at intervals equal to the length of the chalk line used for marking. Use the chalk line to mark a straight line between previously established points. Using a tape measure (measuring wheels are not acceptable), carefully measure the length of each longitudinal elevation survey line to establish end points at 152.4 m, or at a specified length for test sections that are not 152.4 m long, from the previously established Station 0+00. An accurate measurement of this length is required since it is used as a quality control check on the measurement process. Mark a transverse chalk line to connect the end points of two longitudinal lines.
  2.  
  3. Mark a 0.61 m diameter circle centered on the intersection of the marked transverse line and the longitudinal survey line at the end of the section in the left wheel path. At the beginning of the section on the right wheel path, mark a 0.61 m diameter circle centered on the intersection of the longitudinal survey line and the transverse line connecting the left and right wheel paths at Station 0+00. This closure circle will be used for completion of the elevation survey loop.
  4.  
  5. Note the method used to establish the location of the lane center and any discrepancies between painted and measured section end locations on data collection sheet or in the field notebook. This information will help to collect consistent data in future profile measurements at that section.
  6.  

3.3.3 Dipstick ® Operation for Longitudinal Profile Measurements

3.3.3.1 Pre-operational Checks on Dipstick®

Perform the following checks on the Dipstick® prior to testing:

  1. Check the condition of footpads and replace if necessary with an extra set in the Dipstick® case. Clean and lubricate ball and socket joints on the footpads to insure smooth pivoting of the instrument. When a joint is dirty, pivoting becomes difficult and slippage of the footpad can occur. A cleaning agent such as WD-40 or a light oil for lubrication will work for the ball and socket joint.
  2.  
  3. Install a fresh set of rechargeable batteries in the instrument and securely close battery compartment if using a Model 1500 Dipstick® . The batteries in this unit have to be taken out in order to recharge them. The Model 2000 and 2200 Dipstick® is equipped with rechargeable batteries that can be charged while the batteries are still within the unit. If the batteries have not been charged overnight, install a fresh set of rechargeable batteries in the instrument and securely close the battery compartment. Batteries in either of these units should be changed after four hours of usage to insure continuity of measurements. The Model 1500 Dipstick® is powered with 9-volt batteries, while the Model 2000 and 2200 Dipsticks® are powered with AA size batteries. An extra set of rechargeable batteries should be kept on hand for each of these units.
  4.  
  5. Check and, if necessary, retighten the handle on the instrument.
  6.  
  7. Perform Zero Check and Calibration Check, which are described below. According to the manufacturer, the calibration check is needed only if adjustments were required during the zero check. However, for LTPP related measurements, both the zero and calibration checks are required at the beginning of data collection. The Dipstick® should be fully assembled, turned on, and allowed to warm up for several minutes prior to performing these two checks.
  8.  
3.3.3.1.1 Manual Dipstick® (Model 1500):

The operator must perform the zero check on the manual Dipstick® . Form DS-7 (included in appendix D) should be filled when this test is carried out. A zero verification is performed by this test. The test should be performed on a relatively level, smooth, clean, and stable location where instrument can be properly positioned. A suitable fabricated plate or a wood board that can be fitted inside the Dipstick® case can be utilized to perform this check. After positioning the Dipstick® , draw two circles around the footpads and note the reading on the display at the switch end (reading = R1). The instrument should then be rotated 180 degrees and the footpads placed on the two circles that were drawn earlier; note the reading obtained at switch end (reading = R2). If readings from the two placements (R1 and R2) add up to within ± 0.1 mm, the Dipstick® has passed the zero check. If they do not fall within these limits, zero adjustment is necessary.

The zero adjustment should be performed using the following procedure:

  1. Obtain the average of two Dipstick® readings; e = 0.5 (R1 + R2).
  2.  
  3. Subtract the average value from R2 to obtain R2o; R2o = R2 - e
  4.  
  5. Loosen the set screw and adjust start/end pin up or down with the Dipstick® still in the R2 reading position so that display reads R2o.
  6.  
  7. Tighten the set screw, rotate the Dipstick® back to the R1 reading position, and read the display at the switch end (reading = R1o).
  8.  
  9. Repeat the adjustment procedure until the R1o and R2o readings are within the tolerance.
  10.  

This is the only adjustment the operator is allowed to make on the Dipstick® .

The operator must perform the calibration check on the manual Dipstick® .Calibration of the Dipstick® is fixed during manufacture and cannot be altered by the user. The user can verify calibration against a standard calibration block that is provided with the Dipstick® . After the zero check and adjustments are performed, calibration of the device must be checked. The test should be performed on a relatively level, smooth, clean, and stable location where the instrument can be properly positioned. A suitable fabricated plate or a wood board that can be fitted inside the Dipstick® case can be utilized to perform this check. Form DS-7 (see appendix D) should be completed when this test is carried out. To check calibration, note the Dipstick® reading and place the 3.2 mm calibration block under one of the Dipstick® footpads. The reading displayed minus 3.2 should be within ± 0.1 mm of the previous reading. If this tolerance is not obtained, a LTPP Major Maintenance/Repair form (form DS-10 in appendix D) should be completed and the Face Company should be contacted through the RSC office to repair the Dipstick® .

3.3.3.1.2 Automated Dipstick® (Model 2000 and 2200):

The operator must perform the zero check on the automated Dipstick® . This check should be performed on a relatively level, smooth, clean, and stable location where instrument can be properly positioned. A suitable fabricated plate or a wood board that can be fitted inside the Dipstick® case can be utilized to perform this check. Circles should be drawn around the two footpads and the CAL button should be depressed once. The instrument should then be rotated 180 degrees and the two footpads placed in the circles drawn earlier. The CAL button should again be depressed once. The display will flash CAL three times after which the error is automatically stripped out of the readings. Note the reading at switch end of Dipstick® . Rotate Dipstick® and place two footpads in the circles, and note reading at the switch end. If these two readings are within ± 0.1 mm, the Dipstick® has passed the zero check. The zero check can only be performed once after the Dipstick® is turned on. If the check is not successful, the Dipstick® must be turned off and then turned on again, and the zero check repeated. A check mark should be placed on form DS-7 (see appendix D) at the appropriate location to indicate that the zero check was performed.

The operator must perform the calibration check on the manual Dipstick® . Follow the procedure described for the manual Dipstick® (Model 1500) to perform this check. Form DS-7 (see appendix D) should be completed when this test is carried out.

3.3.3.2 Longitudinal Profile Measurement

Complete the header information on form DS-1 (see appendix D). Use guidelines presented in section 3.3.5.2 to enter the header information in form DS-1, except for the air temperature. Use guidelines presented in section 3.3.3.5 to enter the air temperature before and after profile measurements.

The following procedure should be followed to collect longitudinal profile data using the Dipstick® :

  1. Place the Dipstick® on the marked survey line in the right wheel path with the start arrow pointed forward in the direction of traffic and the back edge of the footpad located immediately adjacent to the leave edge of the white stripe at the beginning of the test section to start profile measurement. In this position, the center of the back footpad of the Dipstick® will be at Station 0+00.
  2.  
  3. Record the reading under the right wheel path (RWP) column on form DS-2 (included in appendix D) on the row corresponding to Reading Number 1 after the reading stabilizes. Then rotate the Dipstick® to the next measuring point using a clockwise rotation. The reason a clockwise rotation is specified is because with such a motion the handle of the Dipstick® will not get loose. However, if an operator has any problems in using a clockwise rotation it is acceptable to use a counter clockwise rotation to advance the Dipstick® . If a counter clockwise rotation is used, the operator should check the handle of the Dipstick® at frequent intervals to make sure it is not loose, and if the handle is loose it should be tightened. After the reading has stabilized, it should be recorded on the next row of form DS-2 labeled Reading Number 2. Repeat this procedure for the entire length of the test section. During measurements, the following precautions and procedures should be followed:
    1. Use a consistent motion to advance the Dipstick® (either clockwise or counter clockwise).
    2.  
    3. Hold the handle of Dipstick® in a vertical position when taking measurements.
    4.  
    5. Do not apply lateral pressure to the handle during a measurement.
    6.  
    7. Avoid placing the footpad into a wide crack or a pothole in the pavement. If such a condition is encountered, offset the placement of the footpad so it will rest on the pavement that is adjacent to the feature.
    8.  
    9. Draw circles around both footpads with the start arrow in the direction of traffic at last measurement position if for any reason measurements must be stopped. When restarting, the Dipstick® shall be returned to this position and adjusted so that current measurement agrees with the measurement prior to stoppage.
    10.  
    11. Discard data and restart the measurement procedure if it is not possible to mark the footpad positions prior to stoppage or to successfully reposition the Dipstick® in the same position.
    12.  
  4.  
  5. Compare the location of the back end of front Dipstick® footpad with the location of the transverse line that was marked at the end of the test section after the last measurement in the right wheel path at Station 152.4 m. If the back end of the front footpad is within 275 mm of the marked transverse line, proceed with the transverse closure measurements as indicated in step 4. If the front footpad is not within this interval, perform the following:
    1. Draw circles around each footpad and note the direction of the start arrow.
    2.  
    3. Check the data sheets for skipped or missing measurements.
    4.  
    5. Remeasure the length of longitudinal survey line to verify the position of the end point if no apparent anomalies are present in the data. If the remeasured location of the end point is within 304 mm of the back end of the front footpad of the Dipstick® , remark the transverse line at this location and proceed. If the end point is not within 304 mm of the back end of the front foot, discard the data as suspect and restart the survey from Station 0+00.
    6.  
  6.  
  7. Initiate the transverse closure measurements after the location of the last measurement in the right wheel path has been verified by rotating the rear foot of the Dipstick® toward the left wheel path and placing it on the premarked transverse closure line. Measurements along the transverse closure line should be recorded in the table labeled "Transverse Closure Measurements from Right Wheel Path to Left Wheel Path at Station 152.4 m," which is at the bottom of form DS-6 (included in appendix D). When the Dipstick® reaches the point in which the next measurement along the transverse survey line passes the location of the left wheel path, it should be rotated so that the footpad rests at any point on the closure circle (CC). After recording this measurement in the column labeled 5-CC, rotate the device so that the footpad rests on top of the intersection between the longitudinal survey line in the left wheel path and the transverse closure line. Record this measurement under CC-LWP. This procedure is illustrated in figure 93.
  8.  
  9. Begin measurements along the longitudinal survey line in left wheel path, recording readings in column labeled LWP on forms DS-6 through DS-2. These measurements will be entered in reverse order from those in RWP.
  10.  
  11. Verify that the position of the back edge of the front Dipstick® foot is within 275 mm of end point when the last measurement in left wheel path is made at Station 0+00. If not, follow the procedures for end point verification previously described for the measurements in the right wheel path. If a problem is found with a missing or skipped measurement or final location of the Dipstick® in the left wheel path, measurements in the left wheel path should be discarded as suspect and the survey restarted from the beginning point in the left wheel path.
  12.  
  13. Initiate the transverse closure measurements by rotating the rear foot of the Dipstick® toward the right wheel path and placing it on premarked transverse closure line (located at Station 0+00) after location of the last measurement in the left wheel path has been verified. Measurements along the transverse closure line should be recorded in the table labeled "Transverse Closure Measurements from Left Wheel Path to Right Wheel Path at Station 0+00" which is at the bottom of form DS-2 (included in appendix D). When the Dipstick® reaches the point in which the next measurement along the transverse survey line passes the location of the right wheel path, it should be rotated so that the footpad rests at any point on the closure circle (CC). After recording this measurement in the column labeled 5-CC, rotate the device so that footpad rests on top of the intersection between the longitudinal survey line in the right wheel path and the transverse closure line. Record this measurement under CC-RWP. This procedure is illustrated in figure 93.
  14.  
3.3.3.3. Post Data Collection Check

After completing survey, the operator must conduct the zero and calibration checks.

The following procedure should be followed for performing the zero check for both manual Dipstick® (Model 1500) and automated Dipstick® (Model 2000 and 2200):

  1. Place the Dipstick® on a smooth, clean, and stable location where the instrument can be properly positioned (i.e., carrying case for the Dipstick® or a flat board will suffice).
  2.  
  3. Draw circles around the two footpads and note the reading at the switch end of the instrument (R1).
  4.  
  5. Rotate the instrument 180 degrees and place the two footpads in the circles that were drawn earlier. Note the reading at the switch end of the Dipstick® (R2). The two readings (R1 and R2) should add up to within ± 0.1 mm in order to pass the zero check. If the addition of the two readings is outside these limits, the device has failed the zero check.
  6.  

For both the manual Dipstick® (Model 1500) and the automated Dipstick® (Model 2000 and 2200), the calibration check should be performed as described in section 3.3.3.1 for the manual Dipstick® .

Results from the zero check and the calibration check should be entered on form DS-7 (see appendix D). Based on results from these checks, follow one of the applicable procedures presented below:

  1. If the Dipstick® fails the zero check, data should be discarded as suspect and another survey should be performed.
  2.  
  3. If the Dipstick® passes the zero check, but fails the calibration check, data should be discarded as suspect and the Face Company should be contacted for repair, as discussed under calibration check in section 3.3.3.1.
  4.  
  5. If the Dipstick® passes both tests, the closure error computations that are described in section 3.3.3.4 should be performed.
  6.  

If the Dipstick® failed the zero check, but can successfully be adjusted to pass the zero check and also passes the calibration check, another survey should be performed.

3.3.3.4 Closure Error Computations

The following procedures should be followed when performing closure error computations:

  1. Perform the closure error computations in the field prior to leaving site.
  2.  
  3. Sum and record the readings in each column on forms DS-2 through 6 (see appendix D) in the last row of each column. Measurements in transverse closure measurement tables on forms DS-2 and DS-6 (see appendix D) should be summed across the row and entered in the last column.
  4.  
  5. Enter column summations on form DS-1 (see appendix D) in locations corresponding to labels shown in each summation cell.
  6.  
  7. Add together elevation sums in the RWP and LWP on form DS-1 (see appendix D) and record the result in the indicated cells.
  8.  
  9. Add transverse sums to each of these sums and record the result in the total row at bottom of closure calculation table.
  10.  
  11. Add together the two totals and enter the result into the cell labeled "closure error."
  12.  
  13. Discard data as suspect if the closure error is not within ±76 mm and resurvey the test section until the closure error is within the allowable limits.
  14.  
3.3.3.5 Air Temperature Measurements

Air temperature measurements must be obtained at the start and end of longitudinal Dipstick data collection and recorded on form DS-1. The average of these two temperatures must also be recorded on form DS-1. Air temperature measurements must be obtained using one of the following pieces of equipment:

Measurements should be taken at an adequate distance from any heat source, such as a vehicle engine, vehicle exhaust, and pavement surface. Operators must also ensure that the probe is not held in direct sunlight when allowing the probe to reach a stable value before recording it.

A calibration check of the temperature probe must be performed within 30 days prior to air temperature measurements or whenever the operator observes suspicious temperature readings. A NIST traceable mercury thermometer is required to perform the check. The check should be performed in a shaded area, using the following procedure:

  1. Place the thermometer close to the temperature probe and after they have reached a stable value, observe the readings of the thermometer and probe. If the difference between the two temperature readings is less than or equal to 2 ° C, the temperature probe is considered to be acceptable.
  2.  
  3. Wait at least 5 minutes and repeat steps 1 and 2 if the difference between the two temperatures is greater than 2 ° C. If the difference is still greater than 2 ° C, wait at least five minutes and repeat steps 1 and 2 again. If the difference between the temperatures is still greater than 2 ° C, consider the air temperature probe to be unacceptable and contact the manufacturer of probe to resolve the problem.
  4.  
  5. Perform a cold temperature check if there are any questions regarding the accuracy of the temperature probe. In this check, a plastic bag containing crushed ice is placed around the temperature probe. Allow sufficient time for the temperature probe to stabilize and check the reading displayed. The temperature should be within ± 2 ° C of 0 ° C. If not, consider the air temperature probe to be unacceptable, and contact manufacturer of probe to resolve the problem.
  6.  
  7. Record the results of the calibration check on form DS-11.
  8.  

3.3.4 Site Inspection and Layout—Transverse Profile Measurements

Transverse profile measurements should be performed when manual surveys are conducted on AC surfaced pavements, including rigid pavements with AC overlays. One round of transverse profile measurements should be taken on all LTPP PCC (jointed concrete and continuously reinforced concrete) test sections. The purpose of obtaining transverse profile measurements on PCC sections is to determine the transverse cross slope of pavement.

The pavement must be clear of ice, snow, and puddles of water before profile measurements can be taken with the Dipstick® , as such conditions can affect profile measurements. Pools of water can cause the feet of the Dipstick® to get wet, resulting in a potential for slippage and can also possibly damage electronics in the Dipstick® . Testing under such conditions must be avoided either through adjusting the schedule of profiling trips, or by delaying actual measurements until acceptable conditions exist. Lay out and mark straight lines for the transverse profile measurements. Lines should be perpendicular to edge of the pavement and located at 15.24 m intervals, starting at station zero and ending at station 152.4 m (or end of section if the length of the test sections is greater than 152.4 m). For each test section (GPS or SPS), eleven transverse lines will be present (or more if length of test sections is greater than 152.4 m).

For AC surfaced sections, the location of the transverse lines should be offset to avoid pavement markings and other anomalies such as patches, potholes, and areas that have high severity cracking with missing material. This offset must not exceed 1 m either way. If the anomalies cannot be avoided, the transverse profile is taken at the best location within the allowable offsets. The need for and magnitude of such adjustments must be recorded on form DS-8.

For PCC pavements, the location of the transverse lines should be offset to avoid joints, cracks, and any other localized anomalies like patches and surface defects that would cause the measurements to be nonrepresentative of the transverse profile as related to transverse surface drainage effectiveness. Unlike for AC surfaced pavements, offsets greater than 1 m are allowed for PCC pavements.

3.3.5 Dipstick ® Operation for Transverse Profile Measurements

3.3.5.1 Pre-operational Checks on Dipstick®

The operator should check the equipment using procedures described in section 3.3.3.1. Checks include both the zero check and the calibration check. The operator should fill out the LTPP Dipstick® Data Collection form DS-7 (see appendix D).

3.3.5.2 Entering Header Information in Transverse Profile Form

After performing the preoperational checks on the equipment, the operator should complete the header information in the Transverse Profile Data Collection form (form DS-8 in appendix D). Guidelines for completing this form are presented in this section. As this information is used in ProQual, it is important that the operator strictly follow these guidelines. (Note: The guidelines presented in this section should also be used to complete the header information in form DS-1 that is used for longitudinal profile measurements. However, the air temperature is recorded on form DS-1, while the pavement temperature is recorded on form DS-8).

State Code: Code of State or province in which the site is located.

LTPP Section ID: Four-digit LTPP Section ID of site.

Date: Current date.

Time: Current time, use military format (e.g., 09:30, 15:30. etc).

Dipstick® Serial #: Five digit serial number on base or side of Dipstick® (e.g., 30021).

Dipstick® Model #: 1500 for manual model and 2000 or 2200 for automated model.

Operator: First and last initial of operator in capital letters (e.g., JD).

Recorder: First and last initial of recorder in capital letters (e.g., AM).

Site Type: GPS or SPS.

Visit: Sequential visit identifier. (e.g., A for first visit to site, B for second visit, C for third visit, etc).

Surface Type: A-CC for AC surfaced pavements and P-CC for PCC surfaced pavements.

Condition: Enter the condition of the pavement as either V.GOOD, GOOD, FAIR, or POOR (use capital letters). Use the following guidelines to select condition: (a) V. GOOD—Pavement does not show any distress, (b) GOOD - Pavement exhibits few visible signs of surface deterioration. Pavement may show low severity cracks, (c) FAIR—Typical distresses can include the following in a low to medium severity: rutting, transverse and longitudinal cracking, block cracking, fatigue cracking, edge cracking, and patching, (d) POOR—Typical distresses can include the following in a medium to high severity: rutting, transverse and longitudinal cracking, block cracking, fatigue cracking, patching, and potholes.

Road Name: Highway or route designation in capital letters (e.g., INTERSTATE 57, US 395, S.R. 31).

Lane: Circle either Outside or Inside. The outside lane is the outermost traffic lane. Nearly all LTPP sections are located in the outside lane. The inside lane is any lane that is not an outside lane.

Direction: Direction should be NORTH, EAST, WEST, or SOUTH (use capital letters).

Clouds: Valid entries for this field are CLEAR, P. CLOUDY, or CLOUDY (use capital letters). Use the following guidelines to select an appropriate entry to this field: (a) CLEAR—Sunny sky, (b) P. CLOUDY—sun is sometimes covered by clouds, and (c) CLOUDY—sun cannot be observed.

Temperature: Pavement temperature in degrees Centigrade obtained using an infrared device.

Weather Comment: Any additional comments about the weather conditions at the time of testing. ProQual contains the following built in comments, but the crew is not limited to the use of these comments exclusively: CONDITIONS OK, STEADY CROSSWIND, WIND GUSTS, HOT AND HUMID, HAZY, LOW SUN ANGLE. Use capital letters for weather comments.

3.3.5.3 Transverse Profile Measurement
3.3.5.3.1 AC Surfaced Pavements:

Transverse profile measurements should be collected at the transverse lines that were laid out within the section (see section 3.3.4) starting with the transverse line marked at Station 0+00. Elevations for each transverse profile should be measured from the outside edge of the pavement and should extend over the full lane width, with the actual distance depending on the lane width and pavement striping. The starting point should be the junction of the transverse measurement line and the inside edge of the white paint stripe along the outside edge of the lane. If no outside edge stripe is present, or if the outside edge stripe is on the shoulder, then the beginning point for the measurements should be either the shoulder lane joint or a point approximately 0.91 m from the center of the outside the wheel path. A comment should be entered in the data sheet indicating how the starting point was determined. The starting point on subsequent surveys should be the same. The initial elevation is arbitrarily established as zero and subsequent readings are recorded relative to this benchmark. The combination of these measurements provides a measure of pavement cross slope.

To begin transverse profile measurements, the Dipstick® is placed at outside edge of the pavement starting at Station 0+00 with the start arrow pointed towards the pavement centerline. Measurements should be recorded on the Transverse Profile Data Collection form DS-8 (see appendix D). The operator should complete two runs per transverse profile of each LTPP section; one run up the transverse line and a return run along same line to complete a closed loop survey.

After the last transverse profile measurement is completed, enter any additional comments on the last line of the form. The comment should be entered in capital letters (e.g., ELEVEN DATA POINTS DUE TO HEAVY TRAFFIC).

3.3.5.3.2 PCC Pavements:

Transverse profile measurements should be collected at the transverse lines that were laid out within the section (see section 3.3.4) starting with the transverse line marked at Station 0+00. Measurements should be taken within the lateral extent of the test section measured from the shoulder joint to the centerline longitudinal joint. On widened test sections, the lateral extent of the test section includes the full width (4.3 m) of the slab measured from the shoulder joint to the centerline longitudinal joint.

The starting point for Dipstick® measurements should be the shoulder joint. The initial elevation is arbitrarily established as zero and subsequent readings are recorded relative to this benchmark. To begin transverse profile measurements, the Dipstick® is placed at Station 0+00 at the shoulder joint with the start arrow pointed towards pavement centerline. Measurements should be recorded on the Transverse Profile Data Collection form DS-8 (see appendix D). The operator should complete two runs at each transverse profile location; one run up the transverse line and a return run along the same line to complete a closed loop survey.

After the last transverse profile measurement is completed, enter any additional comments on the last line of the form. The comment should be entered in capital letters (e.g., ELEVEN DATA POINTS DUE TO HEAVY TRAFFIC).

3.3.5.4 Post Data Collection Check

After completing the survey, the operator must conduct zero and calibration checks.

The following procedure should be followed for performing the zero check for both manual Dipstick® (Model 1500) and automated Dipstick® (Model 2000 or 2200):

  1. Place the Dipstick® on a smooth, clean, and stable location where the instrument can be properly positioned (e.g., carrying case for the Dipstick® or a flat board).
  2.  
  3. Draw circles around the two footpads and note the reading at the switch end of the instrument (R1).
  4.  
  5. Rotate the instrument 180 degrees and place the two footpads in the circles that were drawn earlier.
  6.  
  7. Note the reading at the switch end of the Dipstick® (R2). The two readings (R1 and R2) should add up to within ± 0.1 mm in order to pass the zero check. If the addition of the two readings is outside these limits, the device has failed the zero check.
  8.  

For both the manual Dipstick® (Model 1500) and automated Dipstick® (Model 2000 or 2200), the calibration check should be performed as described in section 3.3.3.1 for the manual Dipstick® .

Results of these checks should be entered on form DS-7 (see appendix D). Based on the results from these checks, follow one of the applicable procedures presented below:

  1. If the Dipstick® fails the zero check then data should be discarded as suspect.
  2.  
  3. If the Dipstick® passes the zero check, but fails the calibration check, data should be discarded as suspect and the Face Company should be contacted for repair, as discussed under calibration check in section 3.3.3.1.
  4.  
  5. If the Dipstick® passes both tests, the closure error computations that are described in section 3.3.5.5 should be performed.
  6.  
  7. If the Dipstick® failed the zero check, but can successfully be adjusted to pass the zero check and also passes the calibration check, another survey should be performed.
  8.  
3.3.5.5 Closure Error Computation

The total accumulated error in a transverse profile is established by a closed loop survey. The forward and return run along a transverse line is utilized to compute this error. At each station, sum the readings for the forward and return runs separately, and record the values in the Sum column of form DS-8. Then at each station, add the values in the Sum column for the forward and return run, and record the result in the Closure column. At each station, for each Dipstick® reading, add the reading for the forward and return run, and record the value in the field Difference.

To compute the allowable closure error for a transverse profile run, multiply the total number of Dipstick® readings (sum of number of readings for forward and return run) by 0.076 mm. The allowable closure errors for typical lane widths that are encountered are presented in table 1 .

Table 1. Allowable closure errors for transverse Dipstick® measurements.
Lane Width(m) Total Number of Dipstick® Readings Allowable Closur eError (mm)
3.05 20 ± 1.5
3.35 22 ± 1.7
3.66 24 ± 1.8
3.96 26 ± 2.0

If the closure error for a transverse profile is outside the allowable range, the transverse profile measurements at that location must be repeated once. If the closure error for the repeat run is also outside the allowable range, then the transverse profile line should be offset no more than 1 m and the run repeated once. The value in the Difference field at a specific position gives the difference in readings between the forward and return runs at that position. This information can be used by the operator to identify locations where problem readings may be occurring. If after the offset, the closure error for a transverse profile run is still outside the allowable range, and the Dipstick® is able to pass post data collection checks, enter a comment on why the closure error is outside the allowable value (e.g., ROUGH SURFACE TEXTURE OF CHIP SEAL, MADE CLOSURE DIFFICULT). The data from the third run will be submitted to the FHWA, with a copy to the TSSC. A decision on including that data in the database will be made on a case-by-case basis.

3.3.6 Data Backup

The importance of safeguarding Dipstick® data cannot be overstated. Backup copies of the Dipstick® data sheets for both longitudinal and transverse profile data collection must be made without exception as soon as possible. A minimum of two copies must be made for each data sheet. One copy should be transmitted by mail to the RSC office while the second copy should be retained by the operator in case first copy is lost in the mail.

3.4 ZERO CHECK AND CALIBRATION CHECK

3.4.1 General Background

The zero and calibration checks described in section 3.3.3.1 are performed to ensure that the Dipstick® is operating properly. If the Dipstick® fails the calibration check, it should be returned to the manufacturer for repair.

The RSC should ensure that the gauge block used for the calibration check is calibrated annually to an accuracy of 3.18 ± 0.03 mm using a local calibration laboratory or a calibration micrometer. Calibration of the gauge block may need to be performed more frequently, depending on the presence of oxidation, evidence of corrosion, and possible damage caused by accidental mishandling in the field. If the calibration block is not within an accuracy of 3.18 ± 0.03 mm, a new block that satisfies the criteria should be obtained.

If calibration block thickness is not within 3.18 ± 0.03 mm, all data collected since the last check of the block are suspect and may have to be disregarded.

3.4.2 Frequency of Checks

The zero and calibration checks should be conducted by the operator prior to and after Dipstick® measurements. Procedures for performing the preoperational zero check and calibration check are described in section 3.3.3.1. Procedures for performing the post operational zero check and calibration check are described in section 3.3.3.3. If the Dipstick® fails the calibration check, approval from an RSC engineer is required before shipping equipment to the manufacturer.

3.5 EQUIPMENT MAINTENANCE AND REPAIR

3.5.1 General Background

Scheduled preventive maintenance will serve as a means of ensuring the proper operation of equipment as well as identifying potential problems. Timely identification of problems will help to avoid costly delays or incomplete data that could result from onsite equipment malfunction. Time constraints on the profile testing program require that maintenance activities be performed prior to mobilization for testing. During testing, it is necessary that the operator be constantly aware of proper functioning of equipment. There will be little time to accomplish more than the required initial checks at the site in preparation for test day. Therefore, there is a paramount need for preventive maintenance to be performed on the Dipstick® as a routine function at the end of each test day.

Minimizing the rate of equipment deterioration is the responsibility of the RSC and individual operators. Detailed maintenance procedures are contained in the equipment manuals and the operator must become familiar with these procedures. This section is intended to reinforce the concept of maximum equipment dependability, which is critical to the effectiveness of the LTPP program.

The guidelines presented in this section are not intended to supersede manufacturers' recommendations regarding maintenance, but to provide supplementary service requirements. Where there is a conflict between this guide and the manufacturers' instructions, the more stringent requirements should be followed.

3.5.2 Routine Maintenance

Routine maintenance includes those functions that can be easily performed by the operator with minimal disassembly of the device. Routine maintenance for the Dipstick® includes cleaning and lubrication of ball and socket joints on footpads, replacement of batteries, and cleaning of battery contacts. These items can be performed easily and should always be completed prior to and after operation of equipment.

The following list of pre and post operation preventive maintenance items is not complete, but is intended to show the extent and detail required before equipment checks are performed. This list of items should not supersede manufacturers' minimum requirements for warranty compliance:

  1. Exterior: Check general appearance, glass display (should be clean), and ball and socket joint of footpads (should be properly lubricated).
  2.  
  3. Accessories: Be sure adequate supplies of consumables are on hand (e.g., Batteries, WD-40).
  4.  

3.5.3 Scheduled Major Maintenance

Scheduled major preventive services should include much more than routine checks and will require some disassembly of equipment by personnel with technical capabilities beyond the skill of the operators or RSC staff. The LTPP Major Maintenance/Repair form DS-10 (see appendix D) should be used by the operator to report repairs that are performed. This form will also serve to inform the RSC of the condition of the Dipstick® on a regular basis. Items such as battery connector replacement would fall into the major maintenance category. Appropriate service intervals are outlined in the equipment manufacturer's manual.

3.5.4 Equipment Problems/Repairs

Regardless of the quality of the preventive program, there will probably be equipment failures during the LTPP program. When these occur, it is extremely important that repairs or replacement of items be accomplished in a timely fashion. Such problems can be easily handled during periods when there is no scheduled testing. However, if they occur during mobilization or while onsite, significant problems in scheduling and coordination could develop. To help minimize the impact of equipment problems, it is essential that the operator immediately notify the RSC and any other agencies or individuals about such problems.

Responsibility for equipment maintenance/repair activity rests with each RSC. However, the RSC should keep LTPP staff informed of any major problems concerning equipment. When repairs are necessary and must be performed by an outside agency, the operator should report this information on the LTPP Major Maintenance Report/ Repair form (form DS-10 in appendix D) as an unscheduled maintenance activity.

3.6 RECORD KEEPING

The Dipstick® operator will be responsible for maintaining the following forms/Records:

  1. Longitudinal Profile Measurements: Longitudinal Profile (forms DS-1 through DS-6).
  2.  
  3. Transverse Profile Measurements: Dipstick® Data Collection form - Transverse Profile, (form DS-8).
  4.  
  5. Zero and Calibration Check Records (form DS-7) for both longitudinal and transverse profile measurements.
  6.  
  7. Major Maintenance/Repair form (form DS-10).
  8.  
  9. Air Temperature Probe Calibration Check form (form DS-11).
  10.  

All these forms are included in appendix D. Each of these forms must be kept on files by each RSC with one complete set kept on file at the regional office. The following sections describe each of these forms.

3.6.1 Longitudinal Profile Measurements

Forms DS-1 through DS-6 should be completed at every section where longitudinal profile measurements are performed with a Dipstick® . Follow the guidelines presented in section 3.3.5.2 to fill the header fields in form DS-1. The comments section in this form should include any downtime and any factors that might affect collected data. Names and organizations of other personnel present at the site should be included in this form. Names of these personnel will be invaluable if an accident occurs at the test site. The operator should keep originals of these forms and forward copies to the RSC.

3.6.2 Transverse Profile Measurements

The form DS-8 should be completed at every section where transverse profile measurements are performed. Follow the guidelines presented in section 3.3.5.2 to complete the header fields in this form. The operator should keep the original of this form and forward a copy to the RSC.

3.6.3 Zero and Calibration Check Form

The form DS-7 should be completed whenever the zero and calibration checks are performed.

3.6.4 LTPP Major Maintenance/Repair Form

The form DS-10 must be completed when any major maintenance or repair must be performed by an outside agency.

3.6.5 Air Temperature Probe Calibration Check Form

The form DS-11 must be completed when a calibration check is performed on the temperature probe that is used to measure the air temperature when longitudinal profile measurements are performed with the Dipstick®.

 

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The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
FHWA
United States Department of Transportation - Federal Highway Administration