IFC models of Laurel Subdivision, Laurel Falls, Illinois

324 buildings modeled in 3D from the county GIS building footprints and 52 street-level screenshots of the facades, as input to the Village's shadow study for the IL 347 corridor plan. They are delivered as six georeferenced IFC files with a shared origin. Every model corner lies on its footprint, and 50 photo-based heights are less certain than the ±1.5 ft allowed in the delivery requirements and are flagged in the model.

County GIS footprints and Phase 3 site plan (DWG)52 street-level screenshotsNAD83(2011) Illinois East (ftUS), NAVD 88IFC4, LOD2Prepared Nov 5, 2026

Summary

Georeferencing

All 1,362 model corners lie on the footprints, in six files with one origin

Converted back to State Plane through IfcMapConversion, the IFC corners match the footprints to 0.000 ft. The Phase 3 site plan (LaurelSub_Phase3_Site_Plan.dwg) was drawn in surface coordinates and was scaled to grid with the combined scale factor 0.9999513 before modeling, a shift of about 52 ft in easting and 75 ft in northing.

Heights

50 photo-based heights are less certain than ±1.5 ft

The Village's delivery requirements (p. 4) call for any height less certain than ±1.5 ft to be reported. 24 sheds can't be seen from the street and carry a typical height, 13 buildings are seen only at a steep angle, 7 are hidden by trees and 6 garages are partly blocked.

Check these 50 against LiDAR or field measurements before the shadow study.

Footprints vs. photos

8 buildings differ between the footprints and the screenshots

3 detached garages have footprints but don't appear in the screenshots and were not modeled. 5 accessory buildings appear in the screenshots but have no footprint.

Update the footprint layer for these 8 before the model is used.

The model

Click a building to see the screenshot its height was measured in, how the scale was set and whether the height is uncertain. The tabs below the view show the corner check, which buildings each screenshot covers, the origin in the IFC files and every discrepancy.

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324Buildings in the model
50Uncertain heights, over ±1.5 ft
52Screenshots heights were measured in
6IFC files sharing one origin

Building

Sources and method

Sources

  • LaurelSub_Building_Footprints_2026.dwgBuilding footprints exported from the county GIS, layer BLDG-FOOTPRINT, NAD83(2011) Illinois East (ftUS)279 footprints
  • LaurelSub_Phase3_Site_Plan.dwgPhase 3 site plan from Laurel Falls Homebuilders, LLC, drawn in surface coordinates48 footprints
  • Facade_Screenshots_01-52.zipStreet-level imagery screenshots, one per block face, 1920 × 1080 px52 images
  • County_LiDAR_DEM_2.5ft_NAVD88.tifBare-earth elevation model, 2.5-ft cells, covering the subdivision89 acres
  • Village_3D_Model_Delivery_Requirements.pdfCalls for IFC4 at LOD2, Illinois East zone (1201) NAD83(2011) in US survey feet, NAVD 88, a shared origin and reporting of heights less certain than ±1.5 ft (p. 4)12 pages

Method

  1. Footprints were read as closed polylines from both DWG files. The Phase 3 site plan was brought from surface to grid by multiplying by the combined scale factor 0.9999513 given in its basis-of-coordinates note, then checked against the parcel lines in the county layer.
  2. Each building was matched to the screenshot taken on its block face. The facade width from the footprint set the scale in pixels per foot, and eave and ridge were measured in the same image.
  3. Grade was taken as the lowest elevation model value at the building's corners. Eave and ridge were added as heights above grade in NAVD 88.
  4. Buildings were written as IfcBuilding with walls and roofs extruded from the footprint, one file per area. Every file got the same IfcMapConversion with origin N 1,541,000, E 1,076,000 and elevation 0.
  5. Corners were read back from each IFC file, converted to State Plane and compared with the footprints.

Assumptions and limitations

  • Heights less certain than ±1.5 ft are flagged, per the delivery requirements. Uncertainty is judged from viewing angle, obstruction and scale.
  • Sheds that can't be seen from the street carry a typical height: 8 ft eave and a shed roof.
  • Roofs are simplified to gable, shed or flat (LOD2 in the CityGML sense). Dormers, chimneys and porches are not modeled.
  • The IFC length unit is the US survey foot, matching the State Plane definition, so the Scale in IfcMapConversion is 1. IFC4 has no predefined name for the US survey foot (it was added in IFC 4.3), so it is written as a conversion-based unit with the factor 0.3048006096 m. Confirm that the Village’s software reads it before the files are used.
  • Screenshot capture dates are not known. Buildings that differ between footprints and screenshots should be confirmed in the field.