Initial cartographic draft · editorial review pending
The two archived records for Zaca Fire (2007) give different ways to locate the event. The NIFC feature stores 240,359 GIS acres; the MTBS record stores 242,003 acres. Their outlines share approximately 96,688 hectares, while their combined mapped extent is 98,438 hectares. The question for this draft is: How closely do the agency and satellite boundaries agree?
How closely do the agency and satellite boundaries agree?
| NIFC incident identifier | 938fe0c2-d9ba-4edb-9f0f-a0d9c740e2d4 |
|---|---|
| MTBS fire identifier | CA3469511965920070704 |
| Ignition-date attribute in MTBS | 4 July 2007 |
| NIFC GIS_ACRES attribute | 240,358.7 acres |
| MTBS ACRES attribute | 242,003.0 acres |
| MTBS assessment type | Extended |
| NIFC source / map method | USFS / Unknown |
Where the outlines agree and differ
The intersection is 98.2% of the union of the two projected polygons. Approximately 566 hectares lie inside the NIFC outline alone, and 1,185 hectares lie inside the MTBS outline alone. The NIFC outline spans about 68.8 by 35.6 kilometres in the local map coordinates. These widths and heights describe a bounding rectangle, rather than the route or speed of a fire front.
Reading the two acreage attributes
The MTBS acreage attribute is 1,644.3 acres above the NIFC GIS attribute, a difference of 0.7% relative to NIFC. Those attributes are retained as published by each collection; they are separate from the areas recalculated from the polygons for this overlay. The difference is not an observation of fire growth between two times. For a location-based comparison, examine the two edges as well as the totals. Agreement between these archives does not constitute independent verification of every point along the boundary.
Dates and mapping evidence
The MTBS ignition-date attribute is 4 July 2007. Its mapping record links the following scene identifiers:
- PRE_ID:
504203620050412 - POST_ID:
504203620080420 - PERIM_ID:
504203620070909
The date attribute and scene identifiers provide a route back to the source records. They do not establish a suppression chronology, a containment date, evacuation timing or the date when a particular location burned. This draft has not reconstructed those operational events.
Review before publication
This is an initial cartographic draft. The name, year, source identifiers and spatial overlap have been cross-checked automatically. Before publication, confirm aliases and complex/component relationships against an incident-specific operational record, assess the suitability of the source boundaries, and complete the narrative review. These two collections can share upstream information. The overlap percentage is a geometric comparison, not an evidence-quality score or a measure of ecological damage.
Sources and reproducibility
- NIFC interagency history: this perimeter and its attributes
- USGS / USFS MTBS: this burned-area boundary and mapping attributes
- MTBS product definitions
Method: WGS84 coordinates reprojected to a Lambert azimuthal equal-area projection centred on the NIFC geometry. NIFC query generalization is at most 0.0005 degrees for the original candidates and 0.0001 degrees for supplemental candidates. Metrics use the returned geometries; display outlines are simplified to 45 metres. Polygon intersection divided by polygon union gives the overlap percentage. Values are approximate and are not burn-severity measurements. Source snapshot: 5 November 2026.