A least-squares adjustment can be run on a single connected network of selected parcel lines and on separate, isolated selections of parcel lines. If the adjustment detects isolated networks of parcel lines, it will process them simultaneously.
If the adjustment detects a network of parcel lines that do not connect to any control points, the adjustment will process this network as a consistency check and not as a weighted least-squares analysis.
Isolated parcel networks and the least-squares adjustment
In the graphic below, the two subdivisions will be processed by the least-squares adjustment separately, but in the same session. The network of boundary lines and connection lines attached to the control points A01 and A02 will not be influenced in any way by the network of lines attached to B01 and B02.
This capability avoids the need to iterate through networks and run the adjustment on one network at a time. Processing separate networks simultaneously is also useful when a large seamless boundary network is not available or ready for adjustment. In a parcel fabric, smaller groups of boundary line networks can be adjusted while building, over time, a larger adjustable area.
In the above example, the two isolated parcel networks can be connected to each other to form a single adjustable boundary network by adding a minimum of two connection lines. The connection lines can be added using record-based or survey-sourced COGO dimensions that define the accurate, relative distance between the two networks. In the graphic below, the two isolated parcel boundary networks form a single network with the addition of two connection lines.
Create connection lines across rights-of way
Rights-of-way parcels commonly lie between blocks of parcels, separating them into isolated networks. On the record document there is often no explicit connectivity defined across the right-of way parcels that connect the blocks of parcels. For example, in the graphic below, only the 50 foot width of the right-of-way is recorded on the parcel record document.
When parcels are created from the above parcel record document, the resulting parcel subdivision shown in the graphic below will consist of two parcel blocks, separated by the right-of-way parcel. In many cases, the right-of-way parcel is not created and there is a gap between the inner block (highlighted in green) and outer block of parcels.
When the least-squares adjustment processes this subdivision, the inner and outer parcel blocks will be treated as two separate networks. Since the inner block is not connected to any control points, it will be processed as a consistency check and not as a weighted least-squares analysis.
For the above subdivision to be processed as a single network by the least-squares adjustment, at least two connection lines need to be added between the inner and outer parcel blocks. While there are no connection line measurements described on the original document, the right-of-way width has been recorded and connection line directions can be defined that are parallel to existing parcel boundary lines.
Using the above example, complete the following steps to add connection lines between orthogonal parcel points across rights-of-way:
- Locate pairs of points that are placed directly across the right-of-way from one another and are orthogonally apart.
For example, in the graphic below, the following pair of points are orthogonally 50 feet apart:
- Using the Direction and Distance
tool and a two-point line, create a connection line between the two points.- In the Create Features pane, click the two-point line template
under Connection Lines and click to snap on the first point from which the connection line will be created. - Drag the mouse to start drawing the connection line, right-click, and click Direction/Distance.
- For Horizontal, type a direction that is parallel to the north-south or east-west parcel line, and for Distance, type the road width.
For example, in the graphic below, the Horizontal direction is N1-32-57W, which is parallel to the north-south parcel line, and the Distance is 50 ft (the road width).
- Press Enter to create the connection line.
The resulting connection line must snap to the second point across the right-of-way. If the connection line does not snap to the end point, use the Edit Veritces tool
to move the end point of the connection line to snap to the parcel point. Even though the connection line has been moved, it will still have the correct COGO dimension, which is used by the least-squares adjustment.
- In the Create Features pane, click the two-point line template
Create connection lines between nonorthogonal pairs of points
In the example subdivision above, the inner parcel block needs to be connected to the outer parcel block by at least two connection lines. Since there are no other orthogonal pairs of points to connect, connectivity must be added between point pairs using partial dimensions.
Complete the following steps to add connection lines between non-orthogonal pairs of points:
- Locate a pair of points that are not orthogonal to each other.
For example, in the graphic below, a connection line will be created between the two highlighted points, which are not orthogonal.
- Using the knowledge of the right-of-way width and of the parallel road frontage lines, create two connection lines to connect the parcel points.
The first connection line is created from the first point to the parcel boundary line representing the road frontage line. The direction of the line will match an existing north-south or east-west parcel line and the width will be the road width.
The second connection line is created from the endpoint of the first line to the second, nonorthogonal point. The direction of the second line must match the direction of the parcel line representing the road frontage. The distance of the second connection line is not recorded and should not be added. The second connection line will have a partial COGO dimension with only a direction attribute value.
The graphic below shows an example of connection lines between two nonorthogonal points. The second connection line has a partial COGO direction attribute, which matches the direction of the parcel boundary representing the road frontage. X1 is a new point created from the addition of the two connection lines.
When adding connection lines between nonorthogonal points, the direction on the second connection line shown in the example above is needed to establish the orthogonality with the first line. In the DynAdjust engine, directions sets are processed with the difference between the direction values on two lines, and therefore, the 90-degree angle will be asserted when these lines are processed.
Connection lines and line selections
When running the least-squares adjustment, ensure that connection lines are selected in addition to the parcel lines. If selected parcel polygons are used as input, the least-squares adjustment will only use the lines that bound the polygons as input and connection lines will not be processed.
Selecting and using lines as input ensures that the correct set of lines will be processed and that connection lines will not be excluded.