ifcopenshell.api.georeference.edit_georeferencing#

Module Contents#

class ifcopenshell.api.georeference.edit_georeferencing.Usecase(file, map_conversion=None, projected_crs=None, true_north=None)#

Edits the attributes of a map conversion, projected CRS, and true north

Setting the correct georeferencing parameters is a complex topic and should ideally be done with three parties present: the lead architect, surveyor, and a third-party digital engineer with expertise in IFC to moderate. For more information, read the BlenderBIM Add-on documentation for Georeferencing: https://blenderbim.org/docs/users/georeferencing.html

For more information about the attributes and data types of an IfcMapConversion, consult the IFC documentation.

For more information about the attributes and data types of an IfcProjectedCRS, consult the IFC documentation.

True north is defined as a unitised 2D vector pointing to true north. Note that true north is not part of georeferencing, and is only optionally provided as a reference value, typically for solar analysis.

See ifcopenshell.util.geolocation for more utilities to convert to and from local and map coordinates to check your results.

Parameters
  • map_conversion (dict, optional) – The IfcMapConversion dictionary of attribute names and values you want to edit.

  • projected_crs (dict, optional) – The IfcProjectedCRS dictionary of attribute names and values you want to edit.

  • true_north (list[float]) – A unitised 2D vector, where each ordinate is a float

Returns

None

Return type

None

Example:

ifcopenshell.api.run("georeference.add_georeferencing", model)
# This is the simplest scenario, a defined CRS (GDA2020 / MGA Zone
# 56, typically used in Sydney, Australia) but with no local
# coordinates. This is only recommended for horizontal construction
# projects, not for vertical construction (such as buildings).
ifcopenshell.api.run("georeference.edit_georeferencing", model,
    projected_crs={"Name": "EPSG:7856"})

# For buildings, it is almost always recommended to specify map
# conversion parameters to a false origin and orientation to project
# north. See the diagram in the BlenderBIM Add-on Georeferencing
# documentation for correct calculation of the X Axis Abcissa and
# Ordinate.
ifcopenshell.api.run("georeference.edit_georeferencing", model,
    projected_crs={"Name": "EPSG:7856"},
    map_conversion={
        "Eastings": 335087.17, # The architect nominates a false origin
        "Northings": 6251635.41, # The architect nominates a false origin
        # Note: this is the angle difference between Project North
        # and Grid North. Remember: True North should never be used!
        "XAxisAbscissa": cos(radians(-30)), # The architect nominates a project north
        "XAxisOrdinate": sin(radians(-30)), # The architect nominates a project north
        "Scale": 0.99956, # Ask your surveyor for your site's average combined scale factor!
    })
execute(self)#
set_true_north(self)#