Add a Bearing WKID System Parallel to Spatial Reference WKIDs

[RichardFairhurst]

Summary
ArcGIS needs a Bearing WKID system—parallel to the existing Spatial Reference WKID system—to formally define and standardize how bearings are represented, stored, and interpreted across ArcGIS tools. Today, bearings are treated as raw numbers with no declared semantics. This leads to ambiguity, inconsistent tool outputs, and user confusion. A Bearing WKID system would make bearings portable, self-describing, and reliably interpretable across all ArcGIS workflows.

Why This Matters
Bearings are used in linear referencing, survey workflows, engineering design, CAD/GIS integration, navigation, custom grid systems, field data collection, and event tables. Despite this, ArcGIS provides no standard way to define angular units, reference frame, zero direction, rotation direction, or basis (compass, grid, magnetic, true north, Euclidean, geodetic, engineering grid). A bearing value like “45.0” is meaningless without these semantics.

It is important to note that the spatial reference itself is not a substitute for a well-defined bearing definition. A spatial reference describes how coordinates relate to the earth or a grid, but it does not define how angular directions should be interpreted. Disciplines such as surveying, engineering, navigation, and LRS require bearings to be precise, unambiguous, and consistently applied. Without a dedicated bearing definition system, ArcGIS cannot meet these requirements.

Current Pitfalls in ArcGIS Bearing Handling
1. Bearings are unitless and ambiguous. ArcGIS stores them as plain numbers with no declared meaning.
2. Tools output bearings inconsistently. Different tools use different conventions, often undocumented.
3. Bearings drift toward compass interpretation. When semantics are missing, tools and users assume compass bearings even when the data is grid-based.
4. Metadata is not preserved. Geoprocessing tools often strip metadata, making bearings even harder to interpret.
5. No way to declare custom angular systems. Engineering grids, survey bearings, and custom angular units have no native representation.
6. No validation or error detection. ArcGIS cannot detect mismatches between bearing systems because no standard exists.
7. Bearings are not portable. Exporting or publishing bearing data loses all semantic meaning.

Proposed Solution: A Bearing WKID System
Esri should introduce a Bearing WKID system that works like Spatial Reference WKIDs but for angular semantics. A Bearing WKID would define:
- Angular units (degrees, radians, grads, surveyor’s degrees, custom)
- Reference frame (compass, grid, magnetic, true north, custom)
- Zero direction (north, east, grid X-axis, custom)
- Rotation direction (clockwise or counterclockwise)
- Basis (Euclidean, geodetic, engineering grid)
- Optional parameters (magnetic declination, custom offsets, local engineering definitions)

This would make bearings self-describing, portable, consistent across tools, safe for export and publication, validatable, and future-proof. Just as Spatial Reference WKIDs solved projection ambiguity, Bearing WKIDs would solve bearing ambiguity.

Interim Support: JSON Packaging
Until Esri implements Bearing WKIDs, ArcGIS could support JSON packaging of bearing definitions, use a reserved invalid WKID (such as -1) to signal “custom bearing system,” and adopt a standard JSON schema for storing bearing semantics. This would allow tools and add-ins to interpret bearings safely today while providing a migration path to future Esri WKIDs.

Benefits to the ArcGIS Community
A Bearing WKID system would eliminate silent misinterpretation, standardize bearing outputs across tools, improve engineering and survey workflows, support custom angular systems, make bearings portable and self-describing, reduce user confusion, improve documentation clarity, and align ArcGIS with real-world practices.

Call to Action
If you have ever struggled with inconsistent bearing outputs, undocumented bearing conventions, ambiguous azimuths, grid versus compass confusion, custom engineering bearings, LRS offset calculations, or CAD/GIS integration, please upvote this idea and share your use cases. A Bearing WKID system would bring clarity, consistency, and reliability to one of the most misunderstood parts of ArcGIS.