BHoM
User Feedback - Unit mismatch!
Description:
At present it is not clear to users that their Rhino canvas must be in unit meters for LCA calcs to work properly, leading to inaccurate LCA.
Steps to reproduce:
Set up a millimeters based Rhino canvas and model a 1m3 box. For a material with a QuantityType of Volume and a QuantityTypeValue of 1, the GWP of that box should agree with the GWP of that EPD. Instead it is about ten orders of magnitude off due to the unit mismatch.
Expected behaviour:
At a minimum, user should have to select what units their document is in from an enum, and if its not in meters, Rhino should throw an error telling the user to change their document units. Even better would be a user enum that triggered autoconverts from the incoming units (enum lookup) to meters.
Test file(s):
@ajensen19 this might need to be a documentation issue rather than a bug issue?
BHoM by default is in SI units, the full list of which can be found in the Quantities_oM, with conversions for most units available via the Localisation_Toolkit (available in installers).
So if by default users don't know this, then we should probably document is clearly on the wiki, and in theory all inputs for LCA calculation methods taking in numbers (not objects) should have appropriate quantity attributes stating what unit the input ought to be in. Both of these would be documentation issues rather than bugs?
This does of course assume I have understood the issue correctly, which I might not have done! :smile:
Hi @FraserGreenroyd I can see what you mean and am fine with these being labelled documentation issues. My fear is only that it is the kind of documentation issue that can result in hundreds of thousands orders of magnitude wrong results so I'd like the mechanism to be more forceful than just in the wiki, and perhaps a more explicit feature or catch within the methods. In this case I will also classify this as a feature I guess because I think this is worth a more forceful mechanism in the calculation method. Perhaps using a user-entered "document units" on the LifeCycleAssessmentScope object could be required to confirm proper units before calculation proceeds, or could call a quick unit conversion from native to meters.
I still havent had a chance to confirm how this units issue plays out in a Revit pull but I imagine that is already well known @FraserGreenroyd ? Is this a Rhino specific issue?
@ajensen19 yeah it's generally a Rhino issue where models might not be built in SI. Models pulled from Revit via BHoM are translated to SI as they are pulled, so pulled from Revit models don't experience the same problem :smile:
got it, thanks @FraserGreenroyd , perhaps in this case just a user feedback warning for all Rhino geom would be enough then. thanks!