Aspect Direction Octant Classifier from Slope Components
Downhill compass aspect from explicitly east/north uphill partial derivatives; flat separately reported, half-octant boundaries round clockwise.
Description
Aspect Direction Octant Classifier from Slope Components: return downhill aspect, bearing degrees.
Terrain aspect is the downhill direction, whereas supplied gradients can point uphill. Both the sign and axis convention matter.
This tool returns downhill aspect, bearing degrees. Use the stated units and model convention when interpreting these fields.
When to use this tool
Use this tool when the supplied inputs match the specific operation described above and you need a repeatable result under its stated convention.
- Check the supported input and output contract against an existing calculation or observation.
- Use the complete example to confirm units, selector spelling and result interpretation.
How to use the tool and how it works
- Enter every field in the input table using the stated units and the exact supported selector spelling where applicable.
- Run the tool. Correct input errors before interpreting an output.
- Read the result fields below; use accompanying flags and the stated sign, boundary or model convention when interpreting a number.
Negate eastward and northward uphill gradients, use atan2 to calculate a compass bearing and round it into eight 45-degree sectors. Return flat when both gradients are zero.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| eastwardUphillGradient | Eastward uphill gradient. | Finite number |
| northwardUphillGradient | Northward uphill gradient. | Finite number |
| Output field | Interpretation |
|---|---|
| result | Object containing the following named result fields. |
| result.downhillAspect | Downhill aspect; use the stated units and sign convention. |
| result.bearingDegrees | Bearing degrees; use the stated units and sign convention. |
{
"input": {
"eastwardUphillGradient": 1,
"northwardUphillGradient": 0
},
"output": {
"result": {
"downhillAspect": "W",
"bearingDegrees": 270
}
}
}Limitations and assumptions
- A zero bearing accompanies the flat sentinel and should not be read as a north-facing flat surface.
- Every declared field is required and unexpected fields are rejected. Numeric inputs must be finite; input errors are distinct from a valid false result or an explicitly qualified output.
- Extremely large inputs and nonfinite or excessively large outputs are rejected. List positions reported by the tool use zero-based indices unless stated otherwise.
Alternative or Complementary methods
Check the underlying observations, units and conventions independently before using the result in a larger workflow. The tools listed below address nearby tasks; compare their inputs and scope before substituting one for this operation.
References
Similar or alternative tools
- back bearing calculator
Reverse azimuth, normalized to [0,360), from a forward azimuth in degrees.
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Number of contour crossings per map centimetre from a count along a measured map transect.