Calculating CCTV Scores

The key information in the CCTV data is that of the defects. A list of defects is stored, and a defect scoring approach can be used to judge pipe condition.

To automatically calculate condition grades (displayed on the Scores page of the CCTV Survey Property Sheet) for CCTV Surveys:

1. With the network open, select Calculate CCTV scores/grades from the Network menu.
2. The Data Source dialog will be displayed. Define the selection of CCTV Surveys to be considered for scoring and click OK.
3. The Calculate CCTV Scores/Grades dialog will be displayed:
   • Select the Default scoring method to be used.
   • To use the scoring method corresponding to the method specified in the survey's Standard field, check the option to Select scoring method based on each CCTV Survey's standard.
   • Select whether to score all CCTV Surveys included in the selection defined in the Data Source dialog, or only those surveys that do not already have their Scoring Method field populated .
   • Select the window size for the condition grade profile (if available).

     Note: The condition grade profile is an extension to the scoring for CCTV surveys. In addition to the normal scoring (peak scores, etc.) a survey can be broken down into grades. The percentage of grades present from 1 to 5 can be calculated for each pipe based on a given resolution (the profile window size). The condition grade profile is currently calculated only for structural scores, not for service scores.

   • Click OK.

Defect scoring will be carried out as follows:

If Select scoring method based on each CCTV Survey's standard has not been checked, the Default scoring method will be used.

If Select scoring method based on each CCTV Survey's standard has been checked:

• The Default scoring method will be used when the survey Standard is set to null or an unrecognised standard.
• SRM5 will be used when the survey Standard is set to MSCC3, MSCC4, EN 13508-2:2000, EN 13508-2:2004 or EN13508-2:2003+A1:2011, unless SRM 4 has been chosen as the Default scoring method, in which case SRM4 will be used.

Assumptions about defect lengths are applied as detailed below.

Defect lengths

The MSCC standard makes the following assumptions about defect lengths:

• Point Defects are 1 m long.
• Length of Continuous Defect with missing start tag is assumed to be the length from the start of the pipe to the finish tag.
• Length of Continuous Defect with missing finish tag length is assumed to be the length from the start tag to the end of the pipe.

InfoAsset Manager also applies these assumptions when the chosen CCTV Standard is PACP, EU, WSAA or Custom.

CH2M HILL SCREAM™ - Sewer Condition, A CH2M HILL Technology

The CH2M HILL SCREAM™ standard makes the following assumption about defect lengths:

• Length of Continuous Defect with either start or end tag missing is 1 ft.

InfoAsset Manager also assumes that point defects are 1 ft long.

Likelihood scores

A Likelihood score is calculated, providing an assessment of the likelihood of failure of a pipe. The score is closely related to structural grade and is calculated as follows for the different scoring methods:

• EU, EU2011, MSCC, WSAA, WSAA2, WSAA3 - likelihood score is set to a value calculated by interpolating between the peak/mean scores between grade boundaries
• PACP - likelihood score is set to highest individual defect structural score
• NZWWA - likelihood score is set to structural grade value

• CH2M HILL SCREAM™ - not supported; likelihood is not calculated

The Likelihood score field for a pipe is updated with the value in the CCTV survey field when Updating Pipe Condition from CCTV Data.