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。