What The Format? - Revit Survey & Base Point Coordinate Format - Why Feet & Inch

[Anonymous]

I use to change my base and survey points in revit using coordinates given to me by my surveyor which come to me in either degrees, minutes, seconds or in decimal degrees.  Revit use to allow me to put in decimal degrees into the project & survey points.  Now when I go to put in a coordinate it wants it in feet and inches!  What!?  What use is that?  How would you convert real-world coordinates to feet and inches?  I notice if I paste in my decimal degrees coordinate, it will convert it to feet and inches, but I think all it's doing there is thinking I'm entering decimal feet and converting the decimal to inches.  How would I take a surveyor's coordinates and enter them into Revit?  This is soo irritating and I can't find anything on this as I scour the internet.  Why did this change?  Also, how would I use a spot coordinate to display the actual latitude and longitude of a point.  I don't care how many feet and inches it is from the survey point, I want to know the coordinate at a spot.  How does one accomplish all this?

[ToanDN]

Temporary change the Project Units.

[Anonymous]

Hmm, I understand that this will change it so the survey point will now be in a decimal format, but it's still feet, and what I have from the surveyor is an angular dimension, not a linear dimension.  It doesn't make any sense that a survey point would be done in a length measurement.  Everyone on earth uses angular dimensions for latitude and longitude.  To convert that to a length measurement requires you to know the exact circumference  of the earth along the equator and prime meridian.  I mean, what is Revit doing?

[ToanDN]

Maybe we are talking about different things.  Any point is referenced to a benchmark (whether Survey Point or Project Base Point) by X, Y, Z distances.  It can be translated to a distance, a bearing, and an elevation.  Can you show an example of a point and its format that you want to enter?

And by the way, Revit has been around for decades, so chances are its coordinates units and methodology are acceptable by engineers who are familiar with such things.

[Anonymous]

Sure, so big picture, what I want to do is create a drawing of my current site layout with spot coordinates at my building corners.  The project is near an airport and the FAA wants the coordinates of my building corners so that I can apply for a permit to erect a crane.  I would like these spot coordinates to be in the typical longitude latitude format: Either Decimal Degrees or DMS which everyone is accustom to and which the FAA is asking for.  That is the end goal. 

Since the project is not built yet, I can't just go out with the surveyor and measure the coordinates.

So, what I do have from my civil drawings is the coordinate for a monument near the site in decimal degrees.

My thought then, is to import the CAD file of the civil site plan showing the monument, position my building, which I have in revit, correctly relative to the monument in the civil file, and then place the Revit survey point on that monument, and assign it the real-world coordinates (in decimal degrees for long and lat).

The thought being that now, after having done this, if I pull a spot coordinate at the building corners it would give me the long and lat which I could submit to the FAA for the permit.

The problem is that as it sits, the survey point in revit is really useless for tying the model to the real world as it really only sets up a relative coordinate system.  So for instance, I can place the survey point in my model as previously described and then set it at 0,0 and then pull spot coordinates, but of what use are those coordinates if they are given as length measurements from the survey point?  It doesn't tell me real-world position.  Instead of setting the survey point as 0,0 I could instead convert the long and lat given by the surveyor to distance coordinates with the 0,0 being the intersection of the prime meridian and the equator. This would mean now that the survey point and subsequent spot coordinates in revit would relate to the real world, but then each spot coordinate would have to then be converted back into decimal degrees in order to submit them to the FAA. 

Telling the FAA the long & Lat of the monument, and then the relative distances of the building corners in feet from that point is not going to fly.  That may work to give to subcontractors, but that's not how the FAA permit form wants it.

[ToanDN · Accepted solution]

I don't think Revit can do that.  Everything in Revit relates to one of its own coordinates system (SP or PBP), then this system relates to the "real world" coordinates via acquiring the civil site link shared coordinates.  

So in a sense, you will need a survey plan to acquire the shared coordinates and subsequently, report points in Revit with surveying data.  If you don't have it then you need to seek a different venue such as AutoCAD or Civil3D.

[lukekvasnicka]

I am currently facing the same issue in order to prepare documents for an FAA permit.  Would you mind sharing how you ended up solving your problem to provide the latitude / longitude of your building corners?

[RDAOU]

Autodesk should add that feature but in the meantime you can do one of the following

1. Either ask your surveyor to convert

2. Download mobile app that converts Cartesian coordinates to E/N/EL to GPS 

3. use this site and type in manually https://www.ngs.noaa.gov/NCAT/

4. you convert using formulas to calculate values in a tag (can use Dynamo to fetch the coordinates/parameters and do the conversion then push back into Revit parameters

(R is the radius of the earth)

R = 6371000 + alt

x = R*cos(lat)*cos(lon)

y = R*cos(lat)*sin(lon)

z = R*sin(lat)

lat = asin(z / R)

lon = atan2(y, x)

[boyd_johnson]

@RDAOU   So...I did #3 and went to the NGS website.

1. Moved the pin on the map to the corner of my building on the earth.  Clicked "SUBMIT"
2. It then calculates several conversions below the map...
3. Under SPC, I entered the Northern and Eastern into the Revit Survey Point (usft) - see attached image.

Is this correct?  And is there a way I can verify the model location on the earth?  This directly related to transferring a Revit model to GIS applications.

Thanks, Boyd