---

name: building-change-audit description: > Object-level building change detection between two epochs. Identifies new, demolished, expanded, reduced, split, and merged buildings from footprint vectors. Use when comparing two building datasets, auditing construction changes, or generating building change reports.

Building Change Audit

Compares two epochs of building footprints to detect object-level changes.

Trigger

Use when the user wants to:

• Compare two building datasets for changes
• Identify new/demolished buildings
• Audit construction changes between epochs
• Generate building change statistics

CLI Usage

# Basic comparison
python scripts/building_change_audit.py \
  --before-buildings before.geojson \
  --after-buildings after.geojson

# With custom IoU threshold
python scripts/building_change_audit.py \
  --before-buildings before.geojson \
  --after-buildings after.geojson \
  --match-iou 0.3 --area-tolerance 0.1

# Specify output directory
python scripts/building_change_audit.py \
  --before-buildings before.geojson \
  --after-buildings after.geojson \
  --output-dir ./audit-output

Parameters

Parameter	Default	Description
--before-buildings	required*	Before epoch buildings (GeoJSON/Shapefile)
--after-buildings	required*	After epoch buildings (GeoJSON/Shapefile)
--match-iou	0.1	IoU threshold for matching
--area-tolerance	0.05	Area ratio tolerance for "unchanged"
--bbox	—	Bounding box W,S,E,N for auto-downloading ms-buildings
--date-range	—	Date range START,END for auto-download
--aoi-file	—	AOI polygon file (GeoJSON)
--cache-dir	—	Override the default cache directory
--output-dir	./building-change-output	Output directory

*Required unless --synthetic or --bbox+--date-range is supplied.

Output

File	Description
building_changes.geojson	Change features with type and metrics
report.html	HTML summary report
output-manifest.json	Machine-readable manifest

Change Types

Type	Meaning
new	Building present only in after epoch
demolished	Building present only in before epoch
expanded	Matched, area increased > tolerance
reduced	Matched, area decreased > tolerance
unchanged	Matched, area within tolerance
split	One before → multiple after
merge	Multiple before → one after

Exit Codes

Code	Meaning
0	Success
2	Argument error
3	Dependency missing
6	Data validation failure
7	Processing failure

数据下载

本 skill 可自动从 Microsoft Planetary Computer 下载 Microsoft Building Footprints (ms-buildings) data, generating two snapshots — one for --before-buildings and one for --after-buildings — so you can run a change audit without supplying your own GeoJSON.

python building_change_audit.py --bbox 116,39,117,40 --date-range 2024-06-01,2024-06-30 --output-dir <tmp>

• --bbox W,S,E,N: WGS-84 边界框 (西, 南, 东, 北)
• --date-range START,END: 日期范围 (YYYY-MM-DD,YYYY-MM-DD)
• --aoi-file <path.geojson>: 替代 --bbox 的 GeoJSON 多边形
• --cache-dir <path>: 缓存目录 (默认 ~/.geoskill_cache)

当用户只给 --bbox + --date-range (没有 --before-buildings/--after-buildings) 时， skill 自动下载两份 ms-buildings 数据 (一前一后)。 注意：ms-buildings 是单一静态数据集, 两次下载返回的通常是同一份 parquet blob — 真正的 temporal change detection 需要在脚本外做区域/日期过滤。 由于 ms-buildings 用的是 abfs:// URL (urllib 不支持)，下载会失败并自动 fall back 到 --synthetic 模式。