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map-ruler

Open spatial measurements that testify.

Scale chain → polygon → sealed receipt.
Not a cadastral survey. Roof print ≠ interior GLA.

map-ruler measure --address "Ontario Legislative Building, 111 Wellesley Street West, Toronto, ON, Canada" \
  --feature roof --calibrators basemap,car_sedan --pretty

# Fence / driveway with operator vertices (GeoJSON or [[lat,lon],...])
map-ruler measure --address "..." --feature fence \
  --vertices examples/ontario-demo-fence.json --pretty

# PNG overlay (rings from receipt — no second fetch when coords_latlon present)
map-ruler plot --address "Ontario Legislative Building, 111 Wellesley Street West, Toronto, ON, Canada" \
  --feature roof --out receipts/ontario-demo.png --receipt-out receipts/ontario-demo.json

# Two-point car (or any known length) scale check
map-ruler measure --address "..." --feature roof \
  --scale-segment "43.66250,-79.39120,43.66250,-79.39105" \
  --scale-length-ft 15.5 --pretty

Why

Map UIs draw areas. They rarely defend scale or leave a receipt.

map-ruler is the CDS metrology brick:

  1. Geocode (Nominatim) or accept operator lat/lon
  2. Pull building footprints (OSM Overpass; often Microsoft Building Footprints)
  3. Scale chain — basemap CRS + optional car/parking/dual-basemap protocol
  4. Shoelace area in local meters → sq ft
  5. Seal measure-testify/receipt/v1 with SHA-256

Doctrine: It doesn’t answer. It testifies.

Install

git clone https://github.com/cjchanh/map-ruler.git && cd map-ruler

# pipx (recommended)
bash scripts/install-pipx.sh
# or: pipx install --editable '.[plot]'

# pip editable
python3 -m pip install -e '.[plot]'

# no install
PYTHONPATH=. python3 -m map_ruler measure --address "..." --pretty

Core measure: zero required deps.
Plot + basemap: matplotlib + Pillow (via [plot] extra).
Network: Nominatim + Overpass (+ tile hosts when --basemap).

CLI

# Roof / building footprint near address
python3 -m map_ruler measure \
  --address "Ontario Legislative Building, 111 Wellesley Street West, Toronto, ON, Canada" \
  --feature roof \
  --calibrators basemap,car_sedan \
  --out receipts/ontario-demo.json \
  --pretty

# Pin only
python3 -m map_ruler measure --lat 43.6626213 --lon -79.3910161 --feature building

# Fence / driveway — v0 returns PARTIAL + building context (no auto-trace yet)
python3 -m map_ruler measure --address "..." --feature fence

Features

Feature Behavior
roof / building Closest OSM footprint to pin; GLA band heuristic
fence / driveway Without --vertices: PARTIAL context. With --vertices: CLEAN length (+ area if closed)
parcel Building context (parcel polygons later)
any + --vertices Operator/agent path wins; seals length/area from file

Vertices file shapes

  • GeoJSON LineString / Polygon / Feature (coordinates lon,lat)
  • [[lat, lon], ...] JSON array
  • {"coordinates":[...], "order":"latlon"|"lonlat"}

Calibrators

Id Role
basemap Always on — local equirectangular EN (~2% for small spans)
car_sedan Protocol: 14.5–16.5 ft vehicle as image scale
parking_stall Protocol: ~9×18 ft stall
dual_basemap Protocol: cross-check second imagery source

Combined uncertainty = max of chain (fail-closed, not optimistic RSS).

Receipt schema

See schema/measure-testify-receipt-v1.json.

Status enum: CLEAN | PARTIAL | ABSTAIN | ERROR.

Primary fields:

  • footprint_sqft / footprint_m2
  • gla_band_sqft (0.85–0.95 × footprint, 1-story heuristic)
  • scale_chain[]
  • polygon_sha256
  • receipt_sha256
  • maps links (Google satellite, OSM, Earth)

Agent skill

An operator-side agent skill (author tooling, kept outside this repo) wraps map-ruler for agent invocation when the operator wants a roof/fence/driveway measure with a receipt. The CLI documented above is the complete public interface — nothing in this repo depends on the skill wrapper.

Plot

# True Microsoft/OSM footprints around address
python3 -m map_ruler plot \
  --address "Ontario Legislative Building, 111 Wellesley Street West, Toronto, ON, Canada" \
  --out receipts/ontario-demo-roof.png \
  --receipt-out receipts/ontario-demo-roof.json

# Satellite underlay
python3 -m map_ruler plot --receipt receipts/ontario-demo-roof.json \
  --basemap --basemap-source esri --out receipts/ontario-demo-sat.png

# Fence path on top of context (vertices required for path)
python3 -m map_ruler plot \
  --address "..." --feature fence \
  --vertices examples/ontario-demo-fence.json \
  --out receipts/fence.png

Plot needs matplotlib (+ Pillow for --basemap).

Tests

git clone https://github.com/cjchanh/map-ruler.git && cd map-ruler
python3 -m unittest discover -s tests -v

Offline unit tests only. Live dogfood / plot need network (plot needs matplotlib).

Dogfood

PYTHONPATH=. python3 -m map_ruler measure \
  --address "Ontario Legislative Building, 111 Wellesley Street West, Toronto, ON, Canada" \
  --feature roof --calibrators basemap,car_sedan \
  --out receipts/ontario-demo-roof.json --pretty

License

MIT — see LICENSE.

Disclaimer

Not a survey. Not legal property lines. Not assessor GLA.
Use for operator evidence, agent context, and open research.
Field tape/laser upgrades authority — record it in the scale chain later.