Specify Coordinates at a Point Vague

[Anonymous]

Revit has a feature to Specify Coordinates at a Point in the Manage->Coordinates tab. But, it uses all rather vague input. It doesn't officially describe the coordinate system such as whether it's asking for latitude/ longitude, UTM or other. And, if it is asking for UTM it doesn't ask for the UTM zone and the N/S of equator input which are required inputs for determining the position with UTM. One set of positions could be in several zones. And, there are multiple UTM versions. It's uncertain whether this information is gathered from the Location input because the Location input tool is describes as being used for sun position. And, if these tools were serious then there should be a description somewhere of what UTM zone is being used in the properties. I believe some of the Autocad products use these fields in the GIS data fields.

This makes the tool appear to be decorative, but not accurate or serious tools. How can we verify the results of using this tool?

How do we go about using this Specify Coordinates at a Point tool with all this missing information? Or, should we assume we still need to acquire this information from an Autocad file to actually be accurate?

Thanks,

Tim

[cbcarch]

Read this:

http://paulaubin.com/_downloads/2015_RTC/Aubin_Revit_Coordinates_2016.pdf

[Anonymous]

Thanks for the starter link. I've gone through those type of tutorials already and understand that portion. What's missing from all the documentation are how to identify the input types of the Specify Coordinates at a Point tool. It is not specifying a coordinate system type such as Latitude/ Longitude or North/ Easting the way you would in Civil 3D. And, if it is requiring UTM mapping coordinates (as seems to be suggested by some people), it lacks an input for the required UTM zone number. There are 60 UTM zones. A pair of UTM coordinates is not unique without the zone and N/S of meridian data. Civil 3D seems to require all this information when specifying survey data.

So, to begin with I can't find any documentation for what coordinate type or coordinate system goes into the inputs. All the documentation states to get these values from a surveyor. It shouldn't be that mysterious. Everyone has access to GIS data these days. Then, if it is using UTM data, why is there no place to input zone values. Without the zone values the data has no value to the external world -- it's just more internal relative distances. I've got lots of relative internal distances. But, they have no value to the outside world coordinate systems the way other programs do.

I fully understand that I can acquire and publish coordinates from other Revit and Autocad site files. But, that still gives no value to this Specify Coordinates at Point tool. It seems to only be partially developed, or I'm missing something.

[ToanDN]

Your argument is like an architect going buying some Ikea furniture and complaining the furniture doesn't have any reference to the building levels and grid lines.

[cbcarch]

-Revit is designed to create buildings, not "sites". So, it focuses on the building.

-It is very common in practice in the architecture field to work with Surveyors and Civil engineers, who's primary authoring tool is Civil 3D / Cad for site/infrastructure.

-The workflow described by Paul Aubin works very successfully and hundred, if not thousands of exteremly large/complex projects have been built using Revit and Civil 3D with these methods.

-To ask Autodesk to implement the tool set you are describing into Revit is really not value-adding from my 30 years plus of experience--beginning in 1999 with the pre-Autodesk version of Revit.

-Specify Coordinates at Point does exactly that. Not sure why you need "more"?

[Anonymous]

From reading all the Revit documentation it is explained that the survey point and "Specify Coordinates at a Point" tools are meant for defining global coordinates using GIS data.

From Autodesk Knowledge Network for Revit:

"Survey coordinate system

Use the survey coordinate system to identify the specific location on the earth's surface where your Revit model resides. This coordinate system is defined outside the context of a project."

Revit documentation goes on to explain that a key way you are able to locate the survey point is by using the "Specify Coordinates at a Point" tool. But, if there is no ability to specify the type of map projection system being used ie SPCS 83, UTM, etc then there is no way it can actually be a globally accurate coordinate. The best it can be is a relatively nearby local coordinate on a flat plane. Real GIS global coordinates are mapped from a spherical/ ellipsoid shape onto Longitudes or onto Cartesian coordinates using a mapping system. To use those systems you have to specify the type of mapping system you are using. Then you specify specifics like the mapping zones used. Usually you specify the datum being used (WGS 84), the mapping system you are using (UTM, SPCS 83, etc), and additional information like the zones of the mapping system.

Without this information it is not actually a global coordinate. It's just a local coordinate. But, it's advertised and promoted as using global GIS coordinates mapped to the world. 

From Autodesk Knowledge Network for Revit:

https://knowledge.autodesk.com/support/revit-products/learn-explore/caas/CloudHelp/cloudhelp/2018/EN...

"The survey coordinate system is synonymous with the following terms used by other software applications or in other contexts:

• global coordinates
• GIS coordinates
• grid coordinates
• surveyor coordinates
• projection coordinates
• state plane
• shared coordinates"

[cbcarch · Accepted solution]

Revit's Survey Point is used to locate the Revit Project at a specific point (x,y,z) derived from a Survey ( .dwg) file,

which in itself is tied to the "real" GIS coordinates that you are describing.

This locates the Revit model "realative" to that datum.

This method has been proven to work in the real world.

On a recent project, the CM/GC used the Surveyor's coordinates, the .dwg survey file, and exports to Cad from Revit

to actually locate the building corner on the site for layout purposes.

The building is built,  and there were ZERO complaints form any stakeholders regarding the methods used, software tools or end-product. So, again--I see no value-adding reason to have Revit contain the toolset you are asking for--because it already exists in Civil 3D / AutoCad, which is the primary authoring tool for SITE work.

The Revit model(s) are then tied to this system, which is all that is required for delivery of the job.

[Anonymous · Accepted solution]

Thanks for your reply. I think the only way to figure out how geographic positioning works is to experiment with it. I did some really simple experiments like opening Autocad and creating a new simple site plan DWG and then adding a Gelocation point from a map. This required me to choose the GIS-Coordinate system and the units. In this case I chose UTM83-16F which apparently includes the zone for Chicago, IL as the 16F part.

Next, I inserted it as a link it into Revit and then used the Manage->Acquire Coordinates tool. I chose the linked DWG. Then, I went to Location->Location and Location tab and saw that it was updated with the location including the named GIS Coordinate system being used. That may me feel better that I was finally seeing some acknowledgement of a global coordinate system being recorded in the project. Otherwise, I was beginning to wonder if it was legitimately using GIS or not.

Now that I had the GIS information in Revit, I could then use the Specify Coordinates at Point tool and didn't need to specify GIS system and zone being used because it is already recorded in the project from the Autocad link acquisition. And, when I change the position it keeps assuming that GIS coordinate system is being used even with new coordinates.

So, the way it works is that the only way to assign your GIS coordinate system is by first inserting a link from another program that can assign a GIS coordinate system (like any version of Autocad), and then acquiring position from that file. But, Revit does not offer the opportunity to natively assign a GIS coordinate system in the Specify Coordinates tool. It must be acquired first. Then the tool seems to work ok. I had assumed it worked like Autocad software where you assign the GIS Coordinate system anytime you want. That accounts for my frustrations. I was trying to directly assign a coordinate system using the Revit tools. But, Revit only brings this information inward. It won't originate the data. It apparently won't allow you to natively choose a new GIS coordinate system with any of the tools.

You also can't use the Manage->Location tab to assign the location manually. You can VIEW the GIS coordinate information there after lining and acquiring the data. But, when you assign the location there directly it is only for things like Sun and shadow setting purposes. But, it won't assign GIS data. Oddly, you can view the GIS data there after linking the DWG site file.

There is lots more to learn. But, that was a start.