Irregular Boundary adjustments, along with Grant Boundary adjustments and Angle Points of Meander Lines are secondary methods for establishing the positions of lost corners. Because they may involve any number of lost positions, TPC computes them as part of a traverse adjustment. As a result, they are available only from the Closure View.
You will start with the record data in the traverse you are adjusting. You may have created a second traverse with your retracement data in order to compute the position of the known corner the record data ties back into.
Irregular Boundary adjustments and Grant Boundary adjustments involve adjusting a traverse with record data so that it matches the appropriate retracement points. We can think of this as involving two traverses. One with record calls and another with retracement calls. The adjustment is made to the RECORD data traverse, with a closing point tie to the retracement position of a known corner. In this way, the record data is adjusted to fit the controlling corners then used to compute the positions of the lost corners. Both the record and the retracement traverses start and stop at the same known corners.
Record traverse - contains the record data calls Retrace traverse - contains the retracement measurements
Example: 'Record' traverse with points R1, R2, R3, R4 & R5. 'Retrace' traverse with points T1, T2, T3, T4 & T5. Where T5 is the retraced position of R5.
You will adjust the 'Record' traverse so that it's closing point, R5, ends up at the same position as T5 after the adjustment. To accomplish this, T5 is recalled as the correct closing point in the point to point adjustment of the Record traverse.
Decimal Places and Rounding
TPC uses the Lat/Dep PLSS decimal places in the Program Settings - Decimals Dialog to round the computed sum of departures and latitudes and compute their factors reported in this adjustment.
You can specify more decimal places, consistent with modern day computers, or fewer decimals, consistent with those that may have been used for the Public Lands surveys.
Adjustment Details
If you turn on Adjustment Details, TPC will display the appropriate parameters and individual course adjustments as if you had done the adjustment manually. This will allow you to compare TPC results with similar adjustments from CMM or other methods.
•To see the adjustment details in the Closure View, choose View | Include Closure Data and make sure Adjustment Details is checked.
Reports
TPC reports the intermediate values along with adjusted course data through the Adjustment Details option in the Closure View.
Notice that TPC starts the Adjustment Details with the same intermediate values you would need if you were to adjust the Irregular Boundary manually. The information provide for each adjusted point is identical to any other coordinate adjustment, but in this case, TPC also provides information about the adjustment for each course. Again, this matches the intermediate values you would get if you computed the adjustment manually.
[Adjustment Details]
Irregular Boundary (BLM)
East/West
Retrace - Record: Latitude = -0.690, Departure = -0.440
Factor: Latitude = -0.002878, Departure = 1.001835
Point:1 Desc:orig fnd cnr
Adjusted : N:0.000 E:0.000 Z:0.00
Raw : N:0.000 E:0.000 Z:0.00
Difference: N:0.000 E:0.000 Z:0.00
Linear Error: 0.00 Chains Relative Error: 0
Course 1 to 2
Adjusted Departure = -40.073
Latitude Adjustment = -0.115
Adjusted Latitude = -0.115
Point:2 Desc:
Adjusted : N:-0.115 E:-40.073 Z:0.00
Raw : N:-0.000 E:-40.000 Z:0.00
Difference: N:-0.115 E:-0.073 Z:0.00
Linear Error: 0.14 Chains Relative Error: 294
Course 2 to 3
Adjusted Departure = -17.282
Latitude Adjustment = -0.050
Adjusted Latitude = -0.050
Temporary Points
TPC does not attempt to associate temporary points created in the retracement with the original corners included in the adjusted traverse. You can easily do this with the Random Inverse dialog or insert the adjusted record positions into your retracement traverse as sideshots from their respective temporary points. Either way, you will get the bearings and distances needed to offset the temporary points to their computed positions.
