IMAGENEX DT101Xi, Technical Manual

Page: 17 / 64

Doc no: 430-041-01 17 of 64
Cross-track
𝑐𝑡 =
(𝑎
𝑦
+ 𝑏
𝑦
)
2
(Eq 4)
And
𝑎
𝑦
=
2𝑧
cos
2
(𝛽/2)
× tan (
∅
𝑟
2
)
(Eq 5)
𝑏
𝑦
=
2𝑧
tan(90 − 2∅
𝑟
)
(Eq 6)
Where:
ct = cross-track footprint length (m)
a
y
= cross-track ensonification size at outer beam (m)
b
y
= cross-track ensonification size at nadir (m)
z = water depth (m)
β
= swath angle (°) e.g. 120°
Ø
r
= cross-track beam angle (°)
– (0.75° for DT101/102).
Note that the average is taken between the size at nadir and that at the outer beams.
Long-track
The size of the footprint in the along-track direction is similar to the cross-track and is described by the
following equations (Eq 7, Eq 8, Eq 9):
𝑙𝑡 =
(𝑎
𝑦
+ 𝑏
𝑦
)
2
(Eq 7)
And
𝑎
𝑥
=
2𝑧
cos
2 (𝛽/2)
× tan (
∅
𝑡
2
)
(Eq 8)
𝑏
𝑥
=
2𝑧
tan(90 − 2∅
𝑡
)
(Eq 9)
lt = long-track footprint length (m)
a
x
= long-track ensonification size at outer beam (m)
b
x
= long-track ensonification size at nadir (m)
z = water depth (m)
β
= swath angle (°) e.g. 120°
Ø
t
= along-track beam angle (°)
– (3° for DT101
Xi
/102
Xi
).