Hey All,
Just wanted to ask if folks out there can define the 3 types of units of measure that are displayed in Design File Settings and GCS. Please define what the Linear Units are, the Advanced Settings Resolution units are, and what the GCS units are. Also, what is their relationship with one another?
Linear Units: Are these what you are reading out when measuring? So when I have XY coordinates displayed, they're supposed to be displaying values in whatever unit of measure is listed for Linear?
Advanced Settings Resolution Units: I understand what resolution is, but where does the unit of measure come into play, and more importantly, what is the relationship between this and the Linear Units unit of measure? I assume these and the linear units should match, although I have heard of circumstances where they differ.
GCS: Establishing your GCS is to the effect that you're saying what projection/coordinate system your data is in
Hi Neil,
well, you opened quite complex question ;-)
Neil Usefara said: the 3 types of units of measure
They are not "units of measure" to be precise. In fact, it's about mixing different concepts and to compare apples and oranges.
Neil Usefara said:that are displayed in Design File Settings and GCS.
It would be nice to follow, as Jon asked, the best practices, and to specify used product, its version, and also to provide more precise information what setting do you mean. To share e.g. a picture of dialog or a link to documentation, where the setting is described, makes the discussion simpler and more efficient.
Neil Usefara said:Advanced Settings Resolution Units
General recommendation is "do not touch them", because when you will change them, you will (A) probably corrupt existing model (because its size will change) and (B) there are some consequences when DGN V8 is exported e.g to V7.
These settings describes how values (coordinates) are stored internally in DGN V8 and also provide some basic information what they mean. Default values fit (I guess) 99,9% of scenarios. To change the setting is possible, but it's recommended to know very well how DGN V8 format is designed and what consequences are.
Neil Usefara said:Linear Units
They are units you choose to work with. They do not tell anything more than when a value is used to express a coordinate, what it means for the user (which, typically, is equal what it means in real world).
Working units have no relation to how coordinates are stored, because they are converted into UOR (units of resolution) at background. In other words, when one model uses meters and another millimeters, internal value can be the same.
Neil Usefara said:GCS
GCS system is built on top of working units, and as you wrote, it adds extra information about used geographic coordinate system.
With regards,
Jan
Bentley Accredited Developer: iTwin Platform - AssociateLabyrinth Technology | dev.notes() | cad.point
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!
Neil Usefara said:Customer A's settings are pretty confusing at times
Well, for us, living in strictly metric system, is anything related to feet confusing, even when it's correct :-))))
Neil Usefara said:I still haven't read all the replies in this thread, so these questions may be answered already
I like this discussion, because an experience from real projects, based on feet, was shared, plus some best practices. It's often much better than theory how things works in optimum situation.
I agree fully what e.g. David Allen and Rod Wing wrote: To use wrong seeds is a nightmare. Especially what Rod mentioned - where seed files are in fact converted V7 seeds - cause often weird issues (even in simpler metric settings). I met such problems at my customers too.
I think there are two separate topics now:
Neil Usefara said:If I change Linear Units to Feet from USSF, what does that change?
In general, your understanding is correct: Advanced units are how values are stored, whereas Linear units are how they are presented. So when linear units are changed, geometry should remain the same. But, honestly, I am not sure whether it's always valid when feed and custom (sub)units are used.