A traverse has a closure error if the endpoint of the last leg does not match the traverse start point or the specified closing location. Closure error or misclose is the difference between the endpoint of the last traverse leg and the traverse start point, or the specified closing location.
If a traverse has a misclose distance that is within the specified closure tolerance, it is automatically adjusted to eliminate the misclose by distributing the error among the individual traverse legs.
The closure information of a traverse is displayed under the traverse grid in the Modify Features pane. Misclose Distance is the distance between the endpoint of the traverse and the defined closing location (or start location in a loop traverse). Misclose Ratio is calculated by dividing the misclose distance by the total distance of all lines in the traverse and expressing this value in reciprocal form. The following is an example:
0.89 (misclose distance) ÷ 2466.05 (total length) = 0.00036090 1 ÷ 0.00036090 = 2770.8 Misclose Ratio = 1:2771
A traverse will automatically close and adjust the misclose if the misclose distance is within the specified closure tolerance. To specify a closure tolerance, open the Traverse tool, click Options and click Closure Tolerance. Provide a tolerance and close the Closure Tolerance dialog box. If the endpoint of the traverse lies within the specified misclose tolerance of the defined closing location or start location, the two points are snapped together and the misclose error is adjusted and eliminated.
View adjustment results
If a traverse has a closure error, it is automatically adjusted to eliminate and distribute the misclose among the individual traverse legs. You can view the adjustment results on the Closure tab of the Traverse tool.
On the Closure tab, adjusted dimensions and residual values for each traverse leg are displayed. Residual values indicate how much an individual leg of the traverse had to be adjusted to fit in with the overall adjusted solution. Large residual values can be an indication of erroneous dimensions.
By default, the traverse uses the Compass adjustment method to adjust the misclose. On the Closure tab, you can choose a different adjustment method and apply it to the traverse. To adjust the misclose using a different adjustment method, click the Closure Method drop-down box, choose the method, and click Adjust to apply the new adjustment.
The following adjustment methods are available to distribute closure error in a traverse:
Snap last line to close
The endpoint of the last leg of the traverse is moved to the closing location or start point of the traverse. No adjustment of the traverse is performed.
The Compass adjustment method (default) assumes the dimensions of all legs in the traverse were measured with the same level of precision. The misclose is distributed proportionally to the length of the traverse lines with the assumption being that the greatest error is in the longest lines. The method also assumes that the measurement error occurs equally in both the direction and distance dimensions of the traverse legs. Adjustments are reflected in both the distance and direction values.
Similar to the Compass adjustment method, the Transit adjustment method assumes the dimensions of all legs in the traverse were measured with the same level of precision. The Transit adjustment method, however, assumes there is more error in the distance dimensions than there is in the direction dimensions. Misclose is distributed by adjusting the x,y coordinates of traverse points proportionately to the sum of the x or y values of all the traverse legs. This results in changes that affect both the direction and distance of each leg but will alter the distance to a greater extent.
The Crandall adjustment method assumes direction dimensions to be precise and accurate and closure error occurs from distance dimensions only. Closure error is distributed by adjusting distance dimensions using a least-squares adjustment. The Crandall adjustment method is useful for preserving tangency (tangent curves) in parcels but can produce unexpected results such as reversed directions and large distance adjustments.