The Projected 2D Length is the length of a polyline, only taking into account the (X,Y) coordinates of the vertices and omitting the Z coordinate.
The Projected 2D Length is the sum the 2D length of each segment of the polyline (a segment being defined as the line between two consecutive vertices)
Consider two consecutive vertices V1 and V2 with coordinates (X1, Y1, Z1) and (X2, Y2, Z2). The 2D length of this segment is given by:
√ ((ΔX)2+ (ΔY)2)
ΔX = Χ2 - Χ1
ΔY = Υ2 - Υ1
The Projected 2D Length of the Polyline is calculated by adding the 2D length of the segments:
Lp = L1 + L2 + L3 + … + Lv
Lp = The Projected 2D Length of the polyline.
L1, ..., Lv = The 2D length of the segments.