Map Projection Distortion Tissot Indicatrix Ellipse Axes Note Generator
Summarize caller independently derived Tissot principal scales; does not compute projection derivatives or orientation.
Description
Map Projection Distortion Tissot Indicatrix Ellipse Axes Note Generator: return local axis ratio, local area factor, conformal at point.
A Tissot indicatrix describes local map-projection distortion using principal scale directions. Principal scales determine an axis ratio and an area factor.
This tool returns local axis ratio, local area factor, conformal at point. 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.
Require positive maximum and minimum local scales with maximum at least minimum. Return their ratio, their product and an exact equality test for conformalAtPoint.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| maximumLocalScale | Maximum local scale. | Finite number; greater than zero |
| minimumLocalScale | Minimum local scale. | Finite number; greater than zero |
| Output field | Interpretation |
|---|---|
| result | Object containing the following named result fields. |
| result.localAxisRatio | Local axis ratio; use the stated units and sign convention. |
| result.localAreaFactor | Local area factor; use the stated units and sign convention. |
| result.conformalAtPoint | Exact equality of the supplied principal scales; no global projection analysis. |
{
"input": {
"maximumLocalScale": 2,
"minimumLocalScale": 1
},
"output": {
"result": {
"localAxisRatio": 2,
"localAreaFactor": 2,
"conformalAtPoint": false
}
}
}Limitations and assumptions
- Only supplied local scales are checked; the tool does not derive them from a projection or establish global conformality.
- 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
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