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Thread: 1st post: Revit 2018 GIS coordinates?

  1.    #1
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    1st post: Revit 2018 GIS coordinates?

    What's up guys, I joined here since AUGI seems rather dead lately. I'm "patricks" over on that "other site".

    So what's the deal with the GIS Coordinates listed as a "new feature" for 2018? Based on the videos I've watched on the subject, it looks like exactly the same as what we've always done with regards to placing a CAD file from a civil engineer, locating it correctly, then using Acquire Coordinates.

    Does this mean that the 20-mile from origin warnings have been removed? Does this mean that I no longer have to open Civil files in ACAD and move the drawing close to the actual origin? I haven't installed 2018 just yet, but I really can't tell what's different, just looking at documentation.

  2.    #2
    Mr. Revit OpEd
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    I think it is obtuse but the essence is to connect the Location Dialog with the Coordinates and fundamentally to support the geo-referencing feature that is in AutoCAD. If the DWG file being used as a source has this information Revit can now read that to organize its coordinate system with. Exports to DWG also carry this information from Revit to the exported files.
    Last edited by Steve_Stafford; July 7th, 2017 at 07:01 PM.

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    But I still don't understand how that's different than what I'm doing now in 2017.2.1. I have a civil CAD file. It uses the state GIS coordinate system, with the southwest corner of the site having northing/easting coordinates of something like N 1,8xx,xxx.xx E 1,051,xxx.xx (millions of feet from the GIS coordinate 0,0 point). I link it into Revit (get the 20 mile warning), unpin and move survey to the right place, acquire coordinates, check the Survey Point location (it's correct), and place a Spot Coordinate at that same southwest site corner. Revit reports the exact same coordinates as that point in AutoCAD.

    So what's different in 2018? Is that 20 mile limitation gone? Or is that limitation only for Revit geometry? It is QUITE common to have civil files drawn more than 20 miles from the origin, so it would be nice if it would just not report that error for linked CAD files.

  4.    #4
    Mr. Revit OpEd
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    The 20 mile threshold, no change as far as I know (more on this in a moment).

    There is no obvious difference between how things worked in 2017 and older compared with in 2018. Over the years you may have noticed that the Location Dialog, the one that allows you use a map to locate your project did not do anything at all related to the Shared Coordinate system. All that action did was provide a way for Revit to; originally calculate sun position (and therefore shadows) more believably and more recently to allow for energy analysis estimation to be done.

    Now...assuming the source DWG file is using AutoCAD's GEO Referencing feature it is possible for Revit to inherit this data to affect not only the Location (Sun and Energy Analysis) but also the coordinate location of the project (Shared Coordinates).

    ----

    The 20 mile threshold is a math and computer science problem that Revit developers choose not to lie to us about. They want us to keep the model as close to the file's mathematical origin as possible. External files (and internal modelling) that have data whose extents are larger than 20 miles begin to influence the accuracy of the calculations required to generate and display the model faithfully.

    More often than not a civil file is not really larger than 20 miles. It just has elements that are farther away from the origin than that. Revit doesn't mind that issue and it doesn't mind assigning very large coordinates values to the shared coordinate origin (Survey Point).

    It only cares when there are elements that are beyond the threshold. For example a file that only has two short line segments that are 30 miles apart will cause a warning. A file with an entire set of contour lines 40 miles away from the origin won't cause an error IF all the contours themselves and other annotation don't cause the extent of elements to also be larger than the 20 mile threshold. Distance from the origin is one aspect and the total extent (X,Y AND Z) of the elements in the file is the other.

    Ultimately, the error appears because they want us to know that this external data could negatively affect the accuracy of what we work with inside Revit.

    I wrote THIS POST to discuss how I deal with survey files that violate the threshold. It starts out with one issue (transparent elevations/sections) that occurs when the threshold is crossed.
    Last edited by Steve_Stafford; July 8th, 2017 at 01:29 AM.
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    Member HansLammerts's Avatar
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    Quote Originally Posted by Steve_Stafford View Post
    The 20 mile threshold,..

    ..assuming the source DWG file is using AutoCAD's GEO Referencing feature[/URL] it is possible for Revit to inherit this data to affect not only the Location (Sun and Energy Analysis) but also the location
    The Geomarker definition is a feature that can be found in AutoCAD verticals DWG 2013. Apperently, now this is incorporated in DWG fileformat 2018, is that right Steve? Does Revit 2018 only work with DWG 2018 format for this or does it work with the same technique with the earlier DWG (vertical) fileformats? (If not, it would be a argument to switch to vanilla AutoCAD 2018 to work better together with Revit 2018 as well, imo)

    https://knowledge.autodesk.com/suppo...5EDDC-htm.html
    Last edited by HansLammerts; July 8th, 2017 at 09:00 PM.

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    Quote Originally Posted by Steve_Stafford View Post
    The 20 mile threshold, no change as far as I know (more on this in a moment).

    There is no obvious difference between how things worked in 2017 and older compared with in 2018. Over the years you may have noticed that the Location Dialog, the one that allows you use a map to locate your project did not do anything at all related to the Shared Coordinate system. All that action did was provide a way for Revit to; originally calculate sun position (and therefore shadows) more believably and more recently to allow for energy analysis estimation to be done.

    Now...assuming the source DWG file is using AutoCAD's GEO Referencing feature it is possible for Revit to inherit this data to affect not only the Location (Sun and Energy Analysis) but also the coordinate location of the project (Shared Coordinates).

    ----

    The 20 mile threshold is a math and computer science problem that Revit developers choose not to lie to us about. They want us to keep the model as close to the file's mathematical origin as possible. External files (and internal modelling) that have data whose extents are larger than 20 miles begin to influence the accuracy of the calculations required to generate and display the model faithfully.

    More often than not a civil file is not really larger than 20 miles. It just has elements that are farther away from the origin than that. Revit doesn't mind that issue and it doesn't mind assigning very large coordinates values to the shared coordinate origin (Survey Point).

    It only cares when there are elements that are beyond the threshold. For example a file that only has two short line segments that are 30 miles apart will cause a warning. A file with an entire set of contour lines 40 miles away from the origin won't cause an error IF all the contours themselves and other annotation don't cause the extent of elements to also be larger than the 20 mile threshold. Distance from the origin is one aspect and the total extent (X,Y AND Z) of the elements in the file is the other.

    Ultimately, the error appears because they want us to know that this external data could negatively affect the accuracy of what we work with inside Revit.

    I wrote THIS POST to discuss how I deal with survey files that violate the threshold. It starts out with one issue (transparent elevations/sections) that occurs when the threshold is crossed.
    Ah that makes sense, connect the real world coordinates to the Project Location dialog.

    So if I open a CAD file, turn on all layers and indeed find nothing outside the project limits except being far away from the origin, why does the 20 mile warning still come up when linking the file into Revit?

  7.    #7
    Mr. Revit OpEd
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    Quote Originally Posted by PatrickGSR94
    ...So if I open a CAD file, turn on all layers and indeed find nothing outside the project limits except being far away from the origin, why does the 20 mile warning still come up when linking the file into Revit?...
    I never really know for certain but one common cause: a block has been created badly. I usually avoid spending a lot of time trying to fix the DWG file by going straight to using WBLOCK (in AutoCAD). I select just the relevant site elements I need and the resulting file doesn't have the problem.
    cganiere likes this.

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    Unfortunately I don't know enough about ACAD to know all those commands... I'm barely dangerous enough with EXPLODE

    Will WBLOCK maintain the coordinate system of the Civil engineer's original drawing?

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    ohhh it does maintain the coordinates. Wow, super clean solution this WBLOCK business! Love learning new Revit tricks!

  10.    #10
    Moderator DaveP's Avatar
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    Quote Originally Posted by PatrickGSR94 View Post
    why does the 20 mile warning still come up when linking the file into Revit?
    I often find things in my (wait, not MINE. They're from consultants!) DWGs that have wacked out Z coordinates.
    You not only have to check it in Plan, but switch to the "Front" 3D View and do a Zoom Extents, too.
    Just don't forget to go back to "Plan" when you're done.

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