get surrey base point revit api
StringBuilder sb = new StringBuilder();
IEnumerable<BasePoint> points = new FilteredElementCollector(doc)
.OfClass(typeof(BasePoint))
.Cast<BasePoint>();
foreach(BasePoint bp in points)
{
string name = bp.IsShared? "surveypoint": "project basepoint";
BoundingBoxXYZ bb = bp.get_BoundingBox(null);
XYZ pos = bb.Min;
sb.AppendLine(string.Format("{0} : {1}",name, pos));
}
TaskDialog.Show("debug",sb.ToString());