When pre-validation is performed, Landonline completes two least squares adjustments. The results of these adjustments are summarised under 2 of the following headings:
- Minimally Constrained (Internal Consistency) Adjustment
- Fully Constrained (Partial/Full SDC) Adjustment
- Underlying Survey Consistency Adjustment
Minimally Constrained (Internal Consistency) Adjustment Report
This tests the internal consistency of all survey marks and vectors supplied by you with the CSD (including any adopted boundaries or observations). This is similar to testing traverse and parcel closes. It tests whether points and vectors meet the accuracy standards prescribed by the Cadastral Survey Rules 2021. Specifically:
- Rule 19 – Horizontal accuracy of non-boundary survey marks
- Rule 20 - Horizontal accuracy of connection to control network
- Rule 21 – Horizontal accuracy of boundary referencing
- Rule 27 – Horizontal accuracy of boundary points
For more information on the Internal Consistency Adjustment see the following sections of the ‘Accuracy Rules Tests’ document:
- C182 - Internal Consistency Check
- C182 - Internal Consistency Check Fails
- C182 - Internal Consistency Check Passes with High SEUW
- Misclose Tests
- Accuracy and Proximity Tests
View or download the Accuracy Rules Tests document here:
Accuracy Rule Tests Run During Pre-Validation of CSDs
Fully Constrained (Partial/Full SDC) Adjustment Report
In this test, the underlying nodes that have Survey-accurate Digital Cadastre (SDC) coordinates are held fixed. The compatibility of the new survey data and the SDC coordinates is then tested. A failure in this adjustment indicates the survey measurements do not fit well with the SDC coordinates. A pass in this adjustment means that the resulting coordinates fit well with the SDC coordinates.
For information on SDC status, see:
Survey-accurate digital cadastre (SDC) status
The Standard Error Unit Weight (SEUW) is a guide to the accuracy and precision of the survey. You need to consider the SEUW in relation to the complexity of the dataset and the accuracy of the underlying Landonline data. A value of <1 is an indication of a strong survey.
A failure in this adjustment may indicate a need to assess the underlying data, particularly if the dataset has passed the internal consistency adjustment.
For more information on the full or partial SDC adjustment see the following sections of the ‘Accuracy Rules Tests’ document.
- C184 - Full/Partial SDC Check
- C184 - Full/Partial SDC Check Fails
- Misclose Tests
View or download the Accuracy Rules Tests document here:
Accuracy Rule Tests Run During Pre-Validation of CSDs
Underlying Survey Consistency Adjustment
Sometimes a full or partial SDC check cannot be carried out because the survey dataset does not connect to any SDC marks. When this situation occurs, an underlying survey adjustment is performed.
This adjustment is created by using the observations submitted as part of the survey dataset, as well as the observations from all survey datasets already accepted into Landonline which share at least two marks in common with the new survey dataset. One mark is held fixed in this adjustment.
For more information on the underlying survey adjustment see the following sections of the ‘Accuracy Rules Tests’ document.
- C185 - Underlying Survey Check
- C185 - Underlying Survey Check fails
- Misclose Tests
View or download the Accuracy Rules Tests document here:
Accuracy Rule Tests Run During Pre-Validation of CSDs
Standard Error of Unit Weight
The Standard Error of Unit Weight (SEUW) gives an overall measure of the accuracy of the observations. In the pre-validation report a SEUW of 1.00 indicates that the observations are as good as we expect them to be. A value less than 1.00 indicates that the observations are better than expected and a value greater than 1.00 indicates they are worse. Ideally this number should be less than or near 1.00.
For surveys with full traverse and boundary data the SEUW is often less than 1.00 and for rural surveys, particularly those that incorporate very old adoptions, the figure may be more than 1.00. As long as the data has been captured correctly and complies with the survey regulations, a survey can be accepted with a high SEUW. In such cases, the surveyor should identify work with larger than usual errors in the survey report.
Adjustment error and warning messages
When an adjustment has been run, various error and warning messages may occur in the pre-validation report.
For more information on error and warning messages, see the following section of the ‘Accuracy Rules Tests’ document.
- Adjustment Messages
View or download the Accuracy Rules Tests document here:
Accuracy Rule Tests Run During Pre-Validation of CSDs
Further explanation of the adjustments tests
A thorough explanation of the tests/rules run in in the adjustment panel is included in this document:
Accuracy Rule Tests Run During Pre-Validation of CSDs
The document:
- explains the survey accuracy business rule tests
- explains the adjustment messages
- explains potential causes of failures against accuracy tests
- has not yet been updated to reflect New Landonline.