About the parcel fabric traverse tool
This topic applies to ArcGIS for Desktop Standard and ArcGIS for Desktop Advanced only.
The parcel traverse is the primary method for entering parcel data in the parcel fabric. For a single parcel on a survey plan or record of survey, dimensions for each parcel boundary are entered in sequence such that a closed polygon is formed.
The parcel traverse tool in the parcel editor facilitates data entry of parcels using information from plans and records of survey. Recorded dimensions are entered directly from the plan as well as other parcel information, such as the PIN, stated area, and parcel accuracy.
When entering a parcel traverse, no set of coordinates or knowledge of a spatial reference is needed. All that is required are the parcel dimensions, which are on the plat or record of survey.
Once the parcel traverse is complete, the new parcel can either be saved as unjoined or immediately joined to the parcel fabric. An unjoined parcel resides in local coordinate space outside the parcel fabric layer. When joining a new parcel, parcel corner points are matched with the corresponding points in the parcel fabric.
When entering a parcel traverse in the projected map, you can start entering the parcel anywhere within the map extent or you can snap to existing fabric points. You would snap to existing fabric points for reference purposes when entering a parcel traverse.
If snapping to existing points in the fabric layer when traversing a parcel, the parcel traverse still needs to be a closed loop and the completed parcel still needs to be joined to the fabric.
An incomplete parcel traverse can be saved as unjoined at any time by clicking the Keep changes to parcel data command on the Parcel Details window. After completing a parcel traverse, you can choose to save the traverse and immediately join the parcel to the fabric by clicking the Keep changes command on the Parcel Details dialog box.
Parcel traverse units
The parcel traverse environment supports most of the common units used for representing recorded information on a plat or record of survey. Units are set on the Plan Properties dialog box, and each plan can have a different set of units.
The following direction, angle, distance, and area units are supported:
Direction or angle type
- Quadrant bearing
- North azimuth
- South azimuth
- Internal angle
When entering bearings using the quadrant bearing format, you can use numbers to specify the quadrant instead of having to type the required letters. This allows you to work solely with the numeric keypad and speeds up the data entry process. The following numbers represent the quadrants in the quadrant bearing format:
- 1 = NE
- 2 = SE
- 3 = SW
- 4 = NW
For example, N 45-59-59 E can be entered as 45-59-59-1.
Direction and angle units
- Degrees, minutes, seconds
- Decimal degrees
Distance and length units
- US survey feet
- International feet
- US survey chains
- US survey links
- Square meters
- Square rods
- Square US feet
- Square feet
- Quarter sections
- Square meters, hectares, or kilometers
- Acres, roods, or perches
Circular curve parameters
- Radius and chord length
- Radius and arc length
- Radius and central angle
Circular curve direction
Line categories and feature templates
When entering lines in the parcel traverse grid, you can specify both a line feature template and a line category.
Line categories are defined internally and are used to represent parcel structure. For example, if a series of boundary category lines form a closed loop, a parcel is created. A closed loop of connection category lines does not create a parcel. Line categories are also interpreted by a fabric least-squares adjustment, for example, Road Frontages can be constrained to be collinear.
The following line categories are available in the parcel traverse grid:
- Boundary (line category 0)
Used for the boundary of any closed loop parcel or unclosed parcel in the parcel fabric.
In a fabric least-squares adjustment, the accuracy category of a Boundary is the same as the parcel accuracy category, unless otherwise specified. If no parcel accuracy category is specified, a default accuracy level of 4 is used.
- Dependent (line category 1)
Used for lines that are dependent on parcel boundary lines, for example, easement lines. Dependent lines are part of the parcel, but do not define the boundaries of parcels; that is, a closed loop of dependent lines will not create a parcel.
Dependent lines can optionally participate in a fabric least-squares adjustment, in which case they are treated in the same way as Boundary lines.
- Precise Connection (line category 2)
Used for lines that connect a parcel point to a control point. Precise connections should start at the parcel point and end at the control point and should never start at the control point, that is, be oriented in the reverse direction.
- In a fabric least-squares adjustment, precise connections automatically have an accuracy category that is one level higher than the parcel accuracy category. For example, if the parcel accuracy category is 3, precise connections will have an accuracy category of 2.Caution:
Precise connection lines should not exceed 50 meters (or 164 feet). In a fabric least-squares adjustment, long precise connection lines can effectively constrain the entire adjustment area along the line, making the least-squares adjustment solution unstable. If a precise connection line exceeds 50 meters, it is best to use a standard connection line.
- Connection (line category 3)
Used for lines that connect parcel points. Connection lines are used to add connectivity to the parcel fabric to form a network that can be adjusted in a fabric least-squares adjustment. For example, connection lines are used to connect isolated blocks of parcels. Connection lines are part of the parcels sharing the points to which the connection line connects. Connection lines do not define the boundaries of parcels; that is, a closed loop of connection lines will not create a parcel.
In a fabric least-squares adjustment the accuracy category of connection lines is the same as the parcel accuracy category unless otherwise specified.
- Radial (Line category 4)
Used for lines that radiate out from the end points of curves to the center points of curves. Radial lines are automatically generated and maintained for curved boundaries. Radial lines are only displayed when a parcel is opened.
In a fabric least-squares adjustment the accuracy category of radial lines is the same as the parcel accuracy category unless otherwise specified. For very long radial lines, an accuracy category of 7 (excluded) is recommended. This is because adjustments to long, flat curved boundaries can result in larger shifts in the curve's center points, causing the radial lines to become outliers in an adjustment.
- Road Frontage (Line category 5)
Used for the boundaries of parcels that lie adjacent to roads or right-of-ways. When creating a new parcel, you could use the Road Frontage category instead of using the Boundary category for parcel lines that lie along roads.Note:
Road frontage lines should not be used in unclosed parcels.
In a fabric least-squares adjustment, the accuracy category of road frontages is the same as the parcel accuracy category unless otherwise specified. Road frontages can also be constrained to be collinear in the adjustment.
- Origin Connection (Line category 6)
Used for lines that connect a point of beginning to the starting point of a parcel. When creating a new parcel, an origin connection line is always entered first, then the remaining traverse lines of the parcel are entered.
In a fabric least-squares adjustment the accuracy category of origin connection lines is the same as the parcel accuracy category unless otherwise specified.
- Part Connector (Category 7)
Used lines that connect the parts and/or rings of a multipart or donut parcel. Part connection lines are automatically generated when multipart or donut parcels are migrated to a parcel fabric. When creating a multipart or donut parcel, part connection lines are used to connect parts and/or rings.
In a fabric least-squares adjustment the accuracy category of part connection lines is the same as the parcel accuracy category unless otherwise specified.
In ArcGIS, feature templates are used to create new features. Feature templates help automate the creation of new features in that attributes are automatically populated when templates are specified. In the fabric, you can use feature templates on parcel lines and polygons. For example, you can define a subdivision line template that automatically sets the line category to Boundary and Accuracy to 3.
The curve calculator
When entering a curve for a traverse line, there may not be enough curve parameters stated on the plan or survey document to complete the curve. You can use the Curve Calculator dialog box to determine the complete set of parameters of a curve from two known parameters.
The Curve Calculator command is found on the COGO toolbar.
Parcel traverse closure
When creating a new parcel using the parcel traverse, the end or final traverse point might not exactly match the starting point. The parcel then has a misclose or a parcel traverse closure. Large parcel closures indicate incorrect dimensions in the parcel traverse. When entering parcels using the parcel fabric traverse, parcel closure is displayed at the bottom of the Lines tab of the Parcel Details dialog box.
A parcel traverse in the parcel fabric can be adjusted to eliminate a closure. You can specify which adjustment method to use under the Closure tab on the Parcel Details dialog box. There are three adjustment closure methods that you can choose from:
- The compass adjustment
- The Transit adjustment
- The Crandall adjustment
The compass correction technique specifies that the misclosure, or difference in x and y between the resulting endpoint and the desired endpoint, are equally distributed among the individual two-point arcs and curves that make up the traverse. This is done by adjusting the location and distance of each arc proportional to the difference in closure. The compass correction technique is the technique most often used to resolve errors in misclosure. It assumes that the errors are related to both errors in the direction measurements as well as the distance measurements. Thus, the corrections are reflected in each distance and direction value. This technique is also known as the Bowditch rule.
Much like the compass correction technique, the transit correction method specifies that the misclosure is equally distributed among the individual two-point arcs and curves that make up the traverse. However, this technique favors the direction measurements over the distance measurements. In determining the location change required of each arc, the proportion assigned to each arc is proportional to the total x or y values of all the arcs. This results in changes that will affect both the direction and the distance of each arc but will alter the distance to a greater extent.
The Crandall correction technique is used when the direction values are assumed to be precise and accurate, and any misclosure is due solely to errors in distance measurements. This adjustment will preserve all the direction measurements and will alter only the distance measurements to eliminate the closure error. Since directions are fixed, the Crandall adjustment can result in unexpected results, such as flipped directions, very long distance adjustments, or no adjustment at all. Use an alternative method in these cases.
You can also set the adjustment method that will always be used by default under the Adjustments tab on the Parcel Editor Options dialog box.
Once you have completed a closed loop parcel traverse, you can click the View closure button on the Parcel Details dialog box to view the parcel closure graphically in the edit sketch of the parcel.