Page 21 - 中国仿真学会通讯2020第1期
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in section 4. The last section draws conclusions x - x1n = y - y n = z - z1n = kng ,k n ∈ [0,1] .
and puts forward expectations for further study. x2n - x1n y2n - 1 g
y1n z n - z1n
2
2. Intervisibility Algorithm For the terrain data storing in RSG model
whose interval ( precision ) is Δx = Δy = a,
The intervisibility is acquired by computing intervisibility computing in one GCS tile is broken
the intersections between all of the segments in up into that in several RSGs. The intersection
different GCS tiles and the terrain cured surfaces point between the LoS segment and the current
orderly. Assuming the intersection point RSG ( px,py) is M( x,y) and the line slope is kn
coordinates of the nth segment and the nth GCS tile = ( y2n - y1n ) / ( x n - x1n ) . Then the next intersection
2
are P n ( x1n , y1n , z1n ) and P2n ( x2n , y n , z2n ) point N ( x∗, y∗ ) of the segment and the next
1 2
respectively, the equation of this segment k n can RSG ( p∗x , p ∗ ) can be showed graphically in
g y
be expressed as Figure 1.
Fig.1.All situations of the next intersection point and the next RSG.
The four vertexes of one RSG are ( px, py, condition through bilinear interpolation. The
pz1 ) ,( px +a,py ,pz2 ) ,( px +a,py +a,pz3 ) and ( px , equation of the terrain surface is expressed as
py + a, pz4 ) respectively. Based on these
coordinates, the terrain surface is constructed to Axy + Bx + Cy + D - z = 0,
Where
restore the relatively actual terrain elevation
A = pz1 - pz2 + pz3 - pz4 ,
a2
B = (py + a) ( pz2 - pz1 ) + px( pz4 - pz3 ) ,
a2
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