Cadastral point tolerance checks

Trimble Access provides the ability to check measured or staked out points have been measured twice ("double‑tied") to ensure they meet the appropriate local cadaster regulations for being within tolerance.

To date, this feature has been developed to meet cadaster regulations in Switzerland and in Norway. If your country uses the same cadastral tolerance checking rules you may be able to use this functionality in your own region.

To use this functionality in Trimble Access you will need to add an XML file to the Trimble Data\System Files folder. The XML file defines the cadastral codes and specifies the different tolerance requirements for the type of point being measured or staked.

To help you get started, there are two sample cadastral tolerances XML files – one for Switzerland and one for Norway:

  • The sample CadastralTolerances.xml file:

    • Enables setup of multiple point classes

    • Checks each point has been measured twice

    • Checks each point is within horizontal tolerance

    • Checks the point is within vertical tolerance for some point classes.

  • The sample CadastralTolerances ‑ Norway.xml file:

    • Is set up for a single point class

    • Checks each point has been measured twice

    • Checks each point is within horizontal tolerance

    • Checks for “blunders” or large differences between the two measurements

    • Checks for measurement quality using internal reliability and external reliability calculations

    • Checks that sufficient time has passed between the two measurements of each point

Once you have enabled cadastral tolerance checking in the job, the Trimble Access software automatically checks the tolerances for cadastral points in the job when you stake a point or compute an average of two or more points. The status of each cadastral point is displayed on the map and is summarized in the job screen. For more information on how Trimble Access shows cadastral point status, see Cadastral point status.

To set up the controller so that Trimble Access automatically checks tolerances for cadastral points in the job:

  1. Download the appropriate sample cadastral tolerances XML file from the Configuration files page.

    The sample file provides example codes and includes notes that explain how the file works, and what can be configured. For more information, see Swiss cadastral XML file setup or Norwegian cadastral XML file setup.

  2. Using a text editor, configure the cadastral tolerances XML file to use your codes and tolerance values.

    1. Set up your own codes and make sure the tolerance values in the cadastral tolerances XML file are correct, or modify them to match the tolerance values required.

    2. Make sure the codes in the cadastral tolerances XML file are correctly assigned the classification name that matches the tolerance values required, and modify them as needed.

  3. Copy the modified cadastral tolerances XML file to the Trimble Data\System Files folder on the controller.

    For automatic cadastral point tolerance checking to occur in Trimble Access, the XML file must be named CadastralTolerances.xml. This means that if you download the CadastralTolerances ‑ Norway.xml file, you must rename it to CadastralTolerances.xml before adding it to the Trimble Data\System Files folder on the controller.

For each job that you want to enable automatic cadastral tolerance checks:

  1. Tap and select Job.
  2. Tap Properties.

  3. In the Notes field of the Job properties screen, enter the appropriate cadastral Class name for the cadastral points in the job.

    All cadastral points in the job must use the same cadastral class.

    The Class names are specified just after the <SurveyClasses> line in the cadastral tolerances XML file:

    • CadastralTolerances.xml lists multiple classes, for example TS2.

    • CadastralTolerances ‑ Norway.xml lists one class, ClassA.

  4. Tap Accept.

    The job details panel now includes the Cadastral summary, which shows a color-coded summary of cadastral points in the job.

For any point for which the Code field specifies a cadastral code defined in the cadastral tolerances XML file stored in the System Files folder on the controller, the Trimble Access software automatically performs cadastral tolerance checking when:

  • Staking the point

  • When computing an average, such as:

    • When you compute an average using the Compute average function.

    • When the software detects a duplicate point and from the Action drop-down list you choose to average the points.

The computed errors for the staked or averaged position are compared with the tolerance values recorded for that cadastral code in the cadastral tolerances XML file, and shown in the Tolerance check group box of the As-staked deltas or the Compute average screen.

The color of the point on the map changes to indicate the status of the cadastral point.

Some cadastral regulations may require that each measurement is "independent"for double-tied cadastral points. For conventional surveys, you may be able to achieve this using a different station setup or using the Taped distances feature. For GNSS surveys, you can use the SV subset feature to divide all tracked satellites into two subsets with an even spread throughout the sky, and use one subset to measure and then the other subset to remeasure the point using independent occupations.

The Cadastral summary in the Job details panel in the Jobs screen shows the number of cadastral points in the job, by status.

The map provides immediate feedback on the status of cadastral points.

The display of the colored icons is prioritized so that red is displayed on top of orange, which is displayed on top of green. This means that points out of tolerance or not double‑tied are more visible at any zoom level.

Swiss cadastral point status

When using CadastralTolerances.xml, the color of the point icons provides the following feedback:

  • Green: The point is double‑tied and the averaged measurement is within the defined tolerance values.

  • Orange: Because the point is not double-tied (it has only a single measurement), the tolerance is unknown.

  • Red: The point is double-tied and the averaged measurement is outside the defined tolerance values.

To confirm the defined tolerance, threshold, and time values, refer to the CadastralTolerances.xml file in use on the controller.

Norwegian cadastral point status

When using CadastralTolerances ‑ Norway.xml, the color of the point icons provides the following feedback:

  • Green: The point is double‑tied and:

    • The averaged measurement is within the defined horizontal tolerance.

    • The distance between the two measurements is within the defined tolerance (no blunders detected).

    • The calculated internal and external reliability error values do not exceed the defined thresholds.

    • Sufficient time has elapsed between the two measurements.

  • Orange: The point is either:

    • Double-tied but the calculated internal and external reliability error values exceed the defined thresholds.

    • Not yet double-tied (it has only a single measurement), therefore the tolerance is unknown.

  • Red: The point is double‑tied but at least one of the following is true:

    • The distance between the two measurements exceeds the defined horizontal tolerance.

    • There is an unexpectedly large difference between the two measurements of the point (“blunder” detection).

    • The calculated internal and external reliability error values exceed the defined thresholds.

    • Insufficient time has elapsed between the two measurements.

To confirm the defined tolerance, threshold, and time values, refer to the CadastralTolerances ‑ Norway.xml file in use on the controller.