Align unreferenced spatial data using reviewed control points

Why use this

1. Unreferenced features can be made to line up visually while still carrying unacceptable positional error. Control points clustered in one corner or an incorrect coordinate system can produce a convincing local fit that distorts the rest of the dataset.

2. This job could make alignment choices reviewable through point provenance, residuals and independent checks. Preserving the original geometry lets a GIS reviewer compare alternatives without losing the evidence needed to diagnose a poor transformation.

Why an agent / simpler alternative

Useful judgment

Interpret alignment diagnostics and explain tradeoffs among candidate transformations for qualified review.

Simpler alternative

Assign a known missing CRS directly when the coordinates already use a verified reference system.

Unsuitable when

The output would support surveying, safety or property decisions without independent accuracy validation.

Proposed inputs

1. Name

   Source geometry copy

   Owner

   GIS owner

   Minimum scope

   Scoped vector features and original coordinate metadata

   Quality check

   Preserve an untouched source and note any known distortions.

2. Name

   Control and check points

   Owner

   GIS reviewer

   Minimum scope

   Source/destination pairs, target CRS and accuracy requirements

   Quality check

   Check point distribution and keep independent validation points out of fitting.

Access and setup — proposed or unknown

Proposed minimum

1. Use copied spatial data and a separate output path; propose transformations before altering geometry.

Compatibility unknowns

1. Unknown: QGIS/PyQGIS versions, transformer availability and export compatibility.

External actions requiring approval

1. Installing GIS tools, overwriting layers or publishing location-sensitive datasets.

Expected deliverable and review checks

Proposed artifact

Alignment candidate with transformation parameters, residual table, independent-check results if later run and CRS metadata.

Critical checks

1. Residuals are evaluated against an agreed tolerance and spatial pattern.

2. Output geometry validity and extent are inspected independently of file creation.

Missing output evidence

No new run or output inspection in this editorial layer; see linked source-specific limits.

Failure signals and proposed responses

1. Signal

   Fit points are tightly clustered and distant features warp badly.

   Why it matters

   Small fitted residuals can conceal poor extrapolation.

   Proposed response

   Improve control coverage and hold the output until independent points support the intended area.

2. Signal

   Destination coordinates use a different axis order than expected.

   Why it matters

   The result may be misplaced despite valid numeric inputs.

   Proposed response

   Verify axis conventions and known locations before evaluating transformation quality.

Effort and cost — unknown

Setup work

1. Verify CRS, control provenance and acceptance tolerances.

Ongoing review

1. Review residual patterns and preserve alternative fits for comparison.

Unknowns

1. Unknown: data preparation effort, software setup and achievable site accuracy.

First check — proposed, unexecuted

Status

proposed_unexecuted

Synthetic fixture

Synthetic points include clustered controls and one independent point far from the cluster.

Acceptance checks

1. The review does not accept low fitted residuals alone.

2. A distant mismatch blocks consequential use of the proposed output.

Stop conditions

1. CRS, control provenance or required accuracy cannot be established.

Limits

1. A georeferenced file is not proof of positional accuracy; intended use determines the necessary independent validation.