As the city didn't provide any docs …
http://data.ottawa.ca/dataset/cad-topographic-data
City of Ottawa Open Data Licence Version 2.0
AutoCAD DWG (ack! phbfft!)
MTM (Modified Transverse Mercator), Zone 9. Most likely epsg:2951 - NAD83(CSRS) / MTM zone 9, as other city data sets use it (he adds, naïvely …). Getting this right is critical, unless you want the data shifted a few hundred metres.
- Download: 3.1 GB (tar.gz)
- Expanded: 4.4 GB
- Converted to DXF: 31 GB (AutoCAD 2013, ASCII, via Teigha File Converter)
Mid 2011
Samples: 378035.dwg, 376002.dwg, 356006.dwg
Assumed to be
EEENNN.dwg
where
- EEE - first three digits of MTM easting of lower left corner of tile
- NNN - second to fourth digits of MTM northing of lower left corner of tile (first digit of false northing is always 5).
so lower left corners of files would be
- 378035.dwg - E 378000 N 5035000
- 376002.dwg - E 376000 N 5002000
- 356006.dwg - E 356000 N 5006000
Typically 2 km × 1 km. Note that house outlines are split if they cross tile boundaries, and these would need to be rejoined.
There may be more that I missed out of the 177 total layers
- building
- buildingShapes - these seem to be an aggregate of all the other building layers, so care would be needed not to double import.
- house
- mobile home
- parking garage
- porch
- ruin
- shed
- silo
- spot height (building)
- structure
see layers.txt below
Please see companion gist scruss/glebe-houses-4326.geojson