How to understand Curvature Data in HERE data specifications
Problem
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When working with HERE map content specifications, users may encounter the Curvature attribute and need to understand:
What the curvature value represents
How it is calculated
How to interpret positive and negative values
Whether a given value indicates a sharp or gentle curve
This article explains how curvature values are derived and how they can be interpreted when analyzing road geometry.
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Background
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The Curvature attribute describes the geometric curvature of a road segment or shape point.
It is calculated using the following formula:
Curvature = (1 / Radius in meters) × 1,000,000
Where:
Radius = radius of the curve in meters
Curvature = normalized representation of curve sharpness
Because curvature is inversely proportional to radius:
Smaller radius → Sharper curve
Larger radius → Gentler curve
Higher absolute curvature value → Sharper curve
Curvature value near zero → Straighter road geometry
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Understanding Curvature Values
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### Example
A curvature value of 914
corresponds approximately to a curve radius of:
1,000,000 / 914 ≈ 1,094 meters
This indicates a relatively gentle curve rather than a sharp turn.
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Curvature Direction
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The sign of the curvature value indicates the direction of the curve.
| Value | Meaning |
| --- | --- |
| 0 | Straight segment |
| Positive value | Left curve |
| Negative value | Right curve |
### Important
The direction (positive or negative) is determined relative to the travel direction from the reference node.
This directional interpretation applies only to shape points and should not be applied to node geometry.
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Supported Value Range
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Curvature values are stored within the following range:
-1,000,000 to 1,000,000
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Interpretation Guide
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The following examples illustrate how curvature values relate to curve sharpness.
| Curvature Value | Approximate Radius | Interpretation |
| --- | --- | --- |
| 0 | Infinite | Straight road segment |
| ±500 | ~2,000 m | Very gentle curve |
| ±1,000 | ~1,000 m | Gentle curve |
| ±10,000 | ~100 m | Sharp curve |
| Higher absolute values | Smaller radius | Increasingly sharp curve |
> Note: The sign indicates curve direction, while the absolute value indicates curve sharpness.
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How to Determine Curve Severity
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When evaluating curvature values:
1. Check the magnitude (absolute value) of the curvature.
2. Larger absolute values indicate sharper curves.
3. Smaller absolute values indicate gentler curves.
4. Use the sign to determine the curve direction:
* Positive = Left curve
* Negative = Right curve
Examples:
| Value | Interpretation |
| --- | --- |
| 50 | Nearly straight |
| 914 | Gentle curve |
| 5,000 | Moderate curve |
| 10,000 | Sharp curve |
| -8,000 | Sharp right curve |
| 8,000 | Sharp left curve |
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Validation
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To estimate the actual curve radius from a curvature value:
Radius (meters) =
1,000,000 / |Curvature|
For example:
Curvature = 914
Radius = 1,000,000 / 914 ≈ 1,094 meters
This confirms the road segment represents a relatively gentle curve.
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Additional Information
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Curvature is derived from the geometric shape of the road.
The attribute is intended to provide a normalized indication of curve severity.
Directional interpretation applies only to shape points and is based on the defined travel direction.
A curvature value of zero represents a straight road segment.
Updated 3 days ago