Finding coordinates relative to survey base point and project base point

[senne.vande.sompele]

Hi everybody,

I've been searching alot about this subject (and read alot) but can't find a solution.

I'm trying to find the coordinates for a point relative to the project base point.

I've found how to get them relative to the survey point as following:

ProjectLocation pl = doc.ActiveProjectLocation;
Transform ttr = pl.GetTotalTransform().Inverse;
 ProjectPosition projPosition = doc.ActiveProjectLocation.get_ProjectPosition(new XYZ(0, 0, 0));
LocationPoint loc = element.Location as LocationPoint;
if (loc != null)
{
    XYZ point = ttr.OfPoint(loc.Point);
}

this works perfectly even if I change the "The angle to the true north" but I can't find a way to get the position relative to the project base point.

Has someone have a solution for this?

greets

Senne

[FAIR59]

define function  f(pt) = coordinate relative to surveypoint.

then  point-coordinate relative to project base point = f(pt) - f( project base point)

where 

XYZ location of the project base point .X  = project_base_point.get_Parameter(BuiltInParameter.BASEPOINT_EASTWEST_PARAM).AsDouble());

XYZ location of the project base point .Y  = project_base_point.get_Parameter(BuiltInParameter.BASEPOINT_NORTHSOUTH_PARAM).AsDouble());

XYZ location of the project base point .Z  = project_base_point.get_Parameter(BuiltInParameter.BASEPOINT_ELEVATION_PARAM).AsDouble());

[senne.vande.sompele]

This is correct as long as your angle to the true north is 0°.

After you change this angle the coordinates you get back are not the same as the spot coordinates I have set

[FAIR59]

It should be accurate, even with a rotated true north.

[senne.vande.sompele]

Currently i'm doing the following

var basePoints = doc.NewFilteredElementCollector().OfClass<BasePoint>();
var projectPoint = basePoints.First(x => !x.IsShared);
var surveyPoint = basePoints.First(x => x.IsShared);


var px = projectPoint.get_Parameter(BuiltInParameter.BASEPOINT_EASTWEST_PARAM).AsDouble();
var py = projectPoint.get_Parameter(BuiltInParameter.BASEPOINT_NORTHSOUTH_PARAM).AsDouble();
var pz = projectPoint.get_Parameter(BuiltInParameter.BASEPOINT_ELEVATION_PARAM).AsDouble();
XYZ project = new XYZ(px, py, pz);

var sx = surveyPoint.get_Parameter(BuiltInParameter.BASEPOINT_EASTWEST_PARAM).AsDouble();
var sy = surveyPoint.get_Parameter(BuiltInParameter.BASEPOINT_NORTHSOUTH_PARAM).AsDouble();
var sz = surveyPoint.get_Parameter(BuiltInParameter.BASEPOINT_ELEVATION_PARAM).AsDouble();
XYZ survey = new XYZ(sx, sy, sz);

var projectLocation = doc.ActiveProjectLocation;

          
var surveyPosition = projectLocation.get_ProjectPosition(survey);
survey = new XYZ(-surveyPosition.EastWest, -surveyPosition.NorthSouth, -surveyPosition.Elevation);

ProjectLocation pl = doc.ActiveProjectLocation;
Transform ttr = pl.GetTotalTransform().Inverse;

LocationPoint loc = element.Location as LocationPoint;
if (loc != null)
{
    XYZ point = ttr.OfPoint(loc.Point);
    XYZ projectPoint = ttr.OfPoint(project);
    var x = Math2.FeetToMeters(point.Y - projectPoint.X);
    var y = Math2.FeetToMeters(point.Y - projectPoint.Y);
    var z = Math2.FeetToMeters(point.Z - projectPoint.Z)
}

But this gives me incorrect values for x,y,z

Do you see what i'm doing wrong

[FAIR59 · Accepted solution]

I did some testing, and discovered that the spotcoordinate with origin Project Base doesn't change if the angle to True North changes.

So it's simpler than I thought. The coordinate relative to project base point is in project coordinates. (no Transform required).

XYZ  coord_to_proj_base  =  loc.Point.Subtract( project )

[senne.vande.sompele]

hi I tried that but I think I'm doing something wrong here's the code i'm using:

var basePoints = doc.NewFilteredElementCollector().OfClass<BasePoint>();
var projectPoint = basePoints.First(x => !x.IsShared);

var px = projectPoint.get_Parameter(BuiltInParameter.BASEPOINT_EASTWEST_PARAM).AsDouble();
var py = projectPoint.get_Parameter(BuiltInParameter.BASEPOINT_NORTHSOUTH_PARAM).AsDouble();
var pz = projectPoint.get_Parameter(BuiltInParameter.BASEPOINT_ELEVATION_PARAM).AsDouble();
XYZ project = new XYZ(px, py, pz);

LocationPoint loc = element.Location as LocationPoint;

 XYZ projectPoint = loc.Point.Subtract(project);

[FAIR59 · Accepted solution]

a new way to determine the coordinates of the project base point:

                XYZ project = projectPoint.get_BoundingBox().Min;

[senne.vande.sompele]

Thank you very much that was the solution!