Chapter 13: Geometric Data

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Section 1: Key Points to Know

Geometric Data Defined

Geometric data consists of attributes that describe the highway’s bearing and curve information and descriptive points of a length segment. Geometric attributes are centerline roadbed class and store as point data. This chapter describes the procedures to add, update, or delete these attributes in TRM as other point data.

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Office of Responsibility

TPP is the Office of Primary Responsibility (OPR) for inputting and maintaining all geometric-related data.

Click this link for your district’s TRM analyst.

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Geometric Data Attributes

The table below lists each geometric attribute by category:

Anchor: #i1008423Geometric Data Attribute Name
Baseline Bearing Data	Curve Data
Bearing Type	Curve Type
Bearing Beginning Direction	Delta Angle measurements: Delta Degrees Delta Minutes Delta Seconds Delta Left/Right
Bearing Degrees	Tangent Length 1
Bearing Minutes	Curve Length
Bearing Seconds	Tangent Length 2
Bearing Ending Direction	Curve Degree Angle measurements: Curve Degrees Curve Minutes Curve Seconds
Bearing Location	-

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Definitions

Curve Length—Total length of a curving highway alignment including spiral and normal curves, measured in miles to three decimal places. NOTE: PI curves have no length; they occur at a single point.

Curve Type Values—Indicates the configuration or kind of curve based on the number of points required to define it:

Anchor: #i1008451Curve Type Values
Value	Curve Type	Number of Points
P	PI curve	1 point (change in direction at a point)
N	Normal curve	2 points
S	Spiral curve	3 or 4 points

Curvature Degrees—Whole degree measurement of the rate of curvature, the angle change per one hundred feet, for a given normal curve.

Curvature Minutes—Whole minute measurement of the rate of curvature, the angle change per one hundred feet, for a given normal curve.

Curvature Seconds—Seconds measurement, to one decimal place, of the rate of curvature of a given normal curve.

Delta Degrees—Whole degree measurement of the change in direction at the point of tangency (PT) created by a curve.

Delta Left/Right—Indicates, in increasing reference marker order, the direction a curve turns.

Delta Minutes—Whole minute measurement of the change in direction at the point of tangency (PT) created by a curve.

Delta Seconds—Seconds measurement to one decimal place of the change in direction at the point of tangency (PT) created by a curve.

Tangent Length—The measurement from point of curvature to point of intersection and from point of intersection to point of tangent of a curve.

TS1 Tangent Length—Element whose definition depends on the type of curve being defined:

For a normal curve, the tangent length or distance in miles from the PC or PT to the projection point or intersection of the curve
For a spiral curve, the first spiral tangent length or distance in miles from the TS to the projected point of intersection of the spiral curve.

TS2 Tangent Length—The second spiral tangent length or distance in miles from the ST back to the projected point of intersection of the spiral curve.