Roofing resources
Grade A to D Aerial Measurement Standards Explained
A confidence grade describes the evidence behind a report. It does not establish a universal percentage error.
RoofKarma resource library · Updated
What does a confidence grade mean?
RoofKarma uses A–D confidence labels alongside the reasons, coverage and limitations attached to a report. These are RoofKarma labels, not an independent industry certification.
| Grade | Evidence summary | Use and limitations |
|---|---|---|
| A | Validated high-quality geometry; at most 10% obstruction; closed facets and classified edges; consistency checks pass. | High-confidence measurement. Confirm installation details on site. |
| B | Validated high or medium geometry quality; at most 20% obstruction; all edges classified with limited uncertainty. | Review flagged edges before ordering. |
| C | Lesser support or more obstruction or uncertain edges, with no grade-D condition. | Preliminary estimate. Wider ranges; material ordering withheld. |
| D | Low or unknown geometry quality, excessive obstruction, open facets or failed blocking checks. | Replacement ranges and material orders withheld. A checkbox cannot override this. |
Why do imagery and visibility matter?
Source resolution, capture angle, age and roof visibility affect what can be supported. Tree canopy, shadows and obstructions can hide geometry; capture dates describe the source, not the current roof condition.
What are photogrammetry and orthorectified imagery?
Photogrammetry derives geometry from overlapping images; orthorectification corrects image displacement to support a map view. A top-down image alone does not establish roof pitch or reveal hidden surfaces.
Check whether geometry came from validated aerial photogrammetry, LiDAR or another supported source. Satellite and aerial describe capture platforms, not a guaranteed resolution or measurement accuracy; an image used for display may differ from the geometry source.
Source: USGS: What is an orthoimage?
Does grade A mean 1–2% accuracy?
No universal percentage can be inferred from a grade alone. A defensible numerical accuracy claim requires an applicable study describing the sample, reference measurements, method and error distribution.
What happens with limited evidence?
The report should identify unavailable values and their reasons. Grade-D reports withhold replacement ranges; acknowledging a warning cannot unlock one.