# Detection range / GSD (OSPREY)

Horizon (geometric) from height h (m): d_horizon ~ 3.57*sqrt(h) km.
mast cam at 6 m -> ~8.7 km horizon. small target hull-down beyond that.
add target height for the reverse term but for low contacts it's ~horizon limited.

GSD = pixel_pitch * range / focal_length.
MWIR 25 MP, say 5 um pitch, 100 mm lens, at 5 km:
  GSD = 5e-6 * 5000 / 0.1 = 0.25 m/px. enough pixels-on-target for detect.
Johnson: detect ~1-2 px, classify ~6-8 px. a 10 m boat at 5 km ~ 40 px -> classify ok.

EMCON win: all passive. range is the price. pair w/ KINGFISHER for range when allowed.