function GetPointOnLine(const _distance: Double; const _offset: Double; const _part: Integer): TGIS_Point; virtual; overload;
found point; if _distance < 0, then point will be located before first point of the line; if _distance > Length, then point will be located after last point of the line
Calculate a point located at _distance from the beginning and moved out of line by _offset.
TatukGIS-TGIS_ShapeArc.GetPointOnLine,布布扣,bubuko.com
TatukGIS-TGIS_ShapeArc.GetPointOnLine
原文：http://www.cnblogs.com/chinacodegear/p/3639115.html