Corten, A Survey Navigation System ~J
The most important quality of the subject photographed
which determines exposures and development is its maximum
and minimum brightness. We have as yet no instrument to
measure these. In consequence usual procedures are based
extensively on guess.
ngle, correcting for
plus-computer; also
heading reference
•ue air speed, angle
nent. The wind dis-
ed whenever neces-
adapting it to local
visual and instru-
reference (mostly
oblique angles and
bending by error
tablished by means
wind star vector or
[er drift and speed
f 1 y Z o-
fly a certain abso-
Corrections are applied to p msl and to T m . The correction to p msl is obtained by intro
ducing the local value of QNH for p msl from interpolation of synoptic-meteo values.
The temperature correction should be based on the discrepancy between actual baro
metric mean temperature T m and mean standard ICAO atm. temp. T st for the same height.
T m can be obtained by radiosonde or by measuring T x , T 2 ... T n in the same air mass
during climb and descent, as in figure 3.1.1.
3.1.2 Rate of climb or descent, and
3.1.3 Statoscopy.
Maintaining altitude constancy is facilitated by using the rate of climb indicator as a
check. Statoscopy — altitude differences — can be used as a check as well; it is not an
integral element of the navigation system but, if present for photogrammetric use, its
application in addition to the autopilot’s aneroid can be useful.
3.1.4 Input—Output
iphic latitude
Altitude and
scale
221.15 T m (log p msr log p 0 ) =Z 0
T| + Tg+Tn
n 'm
t t t
INPUT: T, T 2 T n
Pmsl Po
pression for height
oduced in the form
the corresponding
ring flight to real
The input data necessary to obtain exact altitude and scale, are:
T x T 2 . . . T n = COAT at equal pressure intervals
p msl = synoptic estimate for QNH at the survey area in mb
p 0 = static pressure at altitude in mb, measured in terms of pressure altitude
h r = terrain elevation at reference height
c = aerial camera’s principal distance.
The output data obtained and used for altitude and scale are:
T m barometric mean absolute temperature
Z 0 — absolute altitude
Z r = flight height over reference
E„ — reference scale
