Some knowledge of the Thor missile guidance system is needed to understand how these structures on the ground were used, so here's the relevant section from the Bomber Command Strategic Missile School training notes. Sorry, it's the simplest version I've found:
Inertial Guidance System
1. The Inertial Guidance System is the "Navigator" of the Thor, as it has the ability to correct errors in position by comparing a set of pre-calculated figures with others freshly measured during flight. It sends the required corrections in the form of steering signals to the Flight Control System, which is simulating the functions of a "Pilot".
2. The Inertial Guidance System is entirely self contained when in flight, and so interference with its functions, in the form of attempted "jamming", is impossible.
3. After 108.5 seconds of flight the Guidance system takes over control of the missile and when it has calculated that the missile has achieved a velocity which will enable the nose cone to follow a ballistic trajectory to the target, the following signals are produced, in sequence:-
(a) The Pitch Steering signal.
(b) The Yaw Steering signal.
(c) Main Engine Cut-off (and Nose Cone seperation enable)
(d) Vernier Engine Cut-off.
(e) Pre-arm of Warhead in Nose Cone.
4. Missile Axes
(a) The Missile Rolls about its X axis (Longitudinal axis)
(b) The Missile Yaws about its Y axis (Vertical axis)
(c) The Missile Pitches about its Z axis (Horizontal axis)
5. The Gyro Stabilised Platform
The Stable platform is held space referenced during flight by the action of three stabilisation gyros, and an associated servo system. Mounted on it are three accelerometers, which measure individual accelerations along three mutually perpendicular axes.
The X and Y axes of the stable platform are orientated differently to the gimbal axes by 52 degrees, measured anti-clockwise about the pitch gimbal axis. This ensures that the accuracy of the accelerometer is greatest when close to the mean value of the angle of pitch of the missile (Between 40°and 70°).
6. Guidance System Alignment Modes
A mode is a condition of the guidance system. The platform is aligned by each mode in sequence to a progressively increased degree of accuracy.
The mode sequence is:-
The only power entering the guidance system is 115V, 400c/s for the gyro heaters. This will maintain the flourolube at its correct viscosity.
Filament power is applied to all amplifier circuits.
Gyro heater power continues to be applied during this mode, and it is required to be provided until lift-off.
The system will normally remain in in this mode at all times on the Launch Emplacement, but should it be switched "off" for servicing, it must not be advanced into "power on" mode until it has been at least 30 minutes in "standby". If calibration or targeting are required after servicing, the guidance system must remain in "standby" for at least two hours before advancing to "power on".
The missile may be raised or lowered with the guidance system in "standby" condition, provided that no gyro wheel power has been applied in the fifteen minutes immediately preceding movement of the missile.
(c) Power On
An HT supply is applied to all amplifiers, which are now "live" and are available for use.
The Guidance Generator (PU-411) and the Airborne Amplidyne (PU-424) are started from a low voltage DC supply, and these will supply reference power and gimbal torque motor power, respectively.
All voltages may be checked on the digital voltmeter of the MGAC, by turning the selector switch, and the nominal 400c/s of the PU-411, may be checked on the EPUT meter (EPUT = Events Per Unit Time).
Stabilisation gyro float nulling commences, and this can be monitored on the stabilisation gyro float nulling meter, by using the selector switch.
In the "normal" mode of operation, the gimbal position readouts may be "slewed". This gives a check on the operation of the readouts and the associated circuitry.
In the "manual" sub-mode of operation, the repeaters assume the position of their respective gimbals.
(d) Align One
In the "manual" mode, the gimbals may be set to their required positions by manual operation of the slew switches, whilst observing the gimbal position readouts and the gimbal position nullmeters.
The Roll and Pitch gimbals should be set up first, as only azimuth movement of the yaw gimbal is required to "capture" the Short Range Theodolite. Once a signal from the SRT has been obtained, ensure that the gimbal is adjusted to coincide with the "True Null" signal from the SRT. This may be done by checking that the gimbal position nullmeter deflects to the right and left of a centre null, when the manual gimbal handset control is turned very slowly in the same direction.
In "normal" mode, power is applied to the gyro spin motors (wheel power).
In addition, the full facilities of the "manual" sub-mode are still available, but no attempt should be made to slew the gimbals, as there is now a risk of damage being done to the stabilisation gyros.
(e) Align Two
The normal mode provides a coarse automatic alignment of the gimbals. This is achieved by the electrical output signals from the SRT and the vertical sensing element (VSE), which are amplified and can then control the position of the gimbals. As long as the gimbal remains in its correct alignment, no electrical error signals are produced, and no corrective signals are sent to the gimbal torque motors.
The VSE is a form of electrical "plumb line", and its output signals will control the roll and pitch gimbals during horizontal alignment.
Align Two manual mode = Align One normal mode.
(f) Align Three
This mode provides fine electrical alignment of the gimbal positions. The stabilisation gyros enter the gimbal alignment circuit in this mode, and this introduces two major errors:-
(i) Apparent Gyro Precession due to Earth's rotation.
(ii) A large difference in relative axes between the X and Y stabilisation gyros on the stable platform and the gimbals.
To cover error (i) The erection integrators are so arranged as to compensate the position of the gyro stabilised platform for errors due to Earth's rotation. This it does by eliminating all constant errors from the gimbal control circuit, including those due to inaccuracy in manufacture.
Error (ii) is nulled by the resolvers which are referenced to the pitch axis and correct for the relative angular displacement of the gyro axes (and gimbal axes), about the pitch axis.
Before manually advancing the guidance system to this mode, the following must be checked:-
(i) Gimbal position nullmeters at centre of green band.
(ii) Stabilisation gyro nullmeters at centre of the green band.
(iii) Erector integrator potentiometer readouts steady.
The stabilisation gyros are in control of the platform gimbals, and the VSE and SRT signals go to the nullmeters for monitoring purposes.
The missile can be erected or lowered when guidance is in the "Complete Horizontal" mode.
The "Guidance Complete" signal is also produced in this mode, and this is normally required for the countdown to complete Phase One.
(h) In Flight
After lift-off, the airborne stabilisation circuits form closed servo circuits, and are entirely independent of any external control.
The stabilisation gyro compensation voltage is applied in order to correct errors due to manufacturing inaccuracies.
7. Preparation for a Countdown
If the missile is in the "ready" condition, the following will have already been checked, and all that is required is for the LCO to turn the launch sequence start key.
Long Range Theodolite Preparation
(a) Switch "On".
(b) Centre assembly on LRT bench mark.
(c) Check azimuth and elevation readings with required values.
(d) remove lens covers, and open LRT Hut windows.
Short Range Theodolite Preparation
(a) Check that the correct azimuth angle is set into each SRT, as specified in the target data sheet.
(b) Check that the visual optical system is aligned with the collimator, and locked.
(c) Check that the SRTs are mechanically level (Bubble).
(d) Check cables are generally secure.