PART C - TRANSMISSION FACTORS
Ground Dose Rate.
The ground (outside) dose rate is the unshielded dose rate measured 1 meter
above ground level (about waist high).
This dose rate approximates the
average whole body dose rate a soldier would receive if standing in the open
in the contaminated area at the location of the magnitude of a contamination
All dose rates mentioned in radiological intelligence are ground
dose rates unless otherwise specified. All dose-rate information obtained
under conditions that would modify the ground dose rate must be converted to
Factors Affecting Determinations of Ground Dose Rates.
Because some radiation is shielded out, the dose rate inside a vehicle or
shelter is lower than the ground dose rate at that location. The degree of
shielding depends on the type of vehicle or the construction of the shelter.
Dose rates measured in an aircraft flying over a contaminated area are lower
than the corresponding ground dose rates because of the shielding effect of
the air and the aircraft.
A transmission factor (TF) is a measure of the degree of shielding afforded
by a structure, vehicle, fortification, or a set of specified shielding
The transmission factor is that fraction of the outside
(ground) dose or dose rate which is received inside the enclosure providing
A transmission factor (TF) is used to determine the
reduction in the dose received when personnel are protected (shielded) from
Transmission factors for residual radiation have been
established for certain shielding environments and are given in Figure 5-3
on page 5-16.
These transmission factors may be used in determination of
shielded dose or total dose.
a. Determination of Transmission Factors.
Transmission factors for common types of vehicles, structures, or
fortifications are contained in Figure 5-3. These transmission factors were
established for a combat vehicle by determining the shielded dose or dose
rate for the most exposed occupant location.
For a structure or
fortification, by determining the shielded dose or dose rate at
approximately the center of the shielded volume.
determined in the field require two dose rate readings taken about the same
time; one will be an outside (ground) dose rate (OD) reading and the other
an inside (shielded) dose rate (ID) reading.