Relationship between: File Settings > Working Units: (a) Linear Units vs (b) Advanced Settings Resolution vs (c) GCS defined units (Geographic Coordinate System)

Thanks Rod / Thanks Tim

I didn't intend to hi-jack Neil Usefara's thread... but I do feel that if we can somehow quickly determine this information on a group of files, it would be very helpful with isolating files that are using settings that do not to conform to the project settings.

To expand on Jan's explanations above...

Linear Units: Defines the Unit of Measure in MicroStation and MicroStation-based products. Master units are significant where sub-units are less important (more of a user preference: Civil uses decimal feet and architects/structures use fractions of a foot/inches). Which Units (and custom units) are "available" can be defined in an external/configured units.def file. DGN files using different units can be referenced together (MicroStation does the conversion), but I try to avoid if/when possible. All units in MicroStatipon are based on the Meter.

Resolution Units: Defines the size of the Design Plane (2D) (3D = Cube) Pre-V8 DGN, this was defined by pixels 2-32nd power x 2-32 power. User could define the size of a pixel represented, i.e Meter, foot, mile, inch, etc. - which determined the "size" of the Design Plane/Cube. Because this was pixel-based, this was less accurate/did not meet IEEE double-enhanced precision. In my opinion, Resolution in V8/CONNECT units are a carry-over from pre-V8. In my opinion, Units used to define Resolution should match units used to define Working Units

Geographic Coordinate System (GCS): Determines where your project (coordinates) is. States in US may share the same coordinates - but when you define GCS, now MicroStation knows where the project is (in relation to the world system). Most GCS in USA are based on metric units - and then published in Metric units and imperial units (Feet, US Survey Feet) units. Different states use different projection methods. As mentioned, the GCS units must match DGN Working Units - or you will get a unit mismatch alert

Global Origin: Where on the Design Plane/Cube your model is located (center of Design Plane is typically most desired/most accurate)

All of these settings should be set in the seed files/models used for any project. 2D/3D is also set in the seed files/models

Reference Attach - Coincident: Aligns files using coordinates only

Reference Attach - Coincident World: Aligns files using coordinates and global origin

Hope this helps?

This thread also seems helpful for this discussion:

(57) Working Units [FAQ] - MicroStation Wiki - MicroStation - Bentley Communities

Here is another article that, while focused on a particular set of units, explains a little bit about how units are defined, an relate to one another: https://communities.bentley.com/other/old_site_member_blogs/bentley_employees/b/tim_hickmans_blog/posts/survey-feet-vs-international-feet

Jan Šlegr said:

well, you opened quite complex question ;-)

And something you really need to understand completely if you want to get very far with Microstation.

Thanks, Jan.  I am using OpenRoads Designer CONNECT 2020 R3 (10.9).  I currently have a customer "A" who uses an older seed file, with varying units of measure between Linear Units Master Unit and Advanced Settings Resolution Units: 

Customer A's settings are pretty confusing at times, but from what I understand, the reason they have the seed file like this - Before 2017, AutoCAD files did not have the USSF option, therefore when the settings were set to this, there was better acceptance when referencing dwg's in there that did not have the USSF option (pre 2017).  But, when AutoCAD started using USSF, customer A kept doing what they were doing, so there were no issues when referencing files, etc.  

I've got another customer "B" who is using, what I would consider, the more accurate and less convoluted of the two, using the same units for Linear Units and Advanced Settings (they also have a better resolution for what type of work we're doing):

I essentially just wanted to know what Linear Units and Advanced Settings units do and mean.  If I change Linear Units to Feet from USSF, what does that change?  And visa versa.  From what you typed, I'm gathering that Linear Units are how the numbers are read out/measure in the Model and Advanced Settings are how the units are broken down for accuracy/resolution.  I still haven't read all the replies in this thread, so these questions may be answered already - but I will still post this.

Thanks!