Navigation Orientation & Position

© Brooke Clarke, N6GCE




Determining you position on the Earth (or elsewhere) is an exercise that depends on the interrelationship between time and position.  For example if you know the exact time and can sight a heavenly body with a Sextant then you can determine where on Earth you are. If you know were you are, on a Sunny day you can tell what time it is using a Sundial.  Because of the importance of Navigation at sea the British offered what today would be at $10 million reward for a clock that would be practical at sea to find the Longitude.  The pendulum clock would not work at sea.  Harrison spent most of his productive life developing clocks that would work at sea.

For precision time transfer you need to know where you are then you can determine what time it is.  Because of this radio based time transfer methods follow the navigation systems.  When Loarn-C was the best nav system it was also the best time transfer method.  Now the GPS system was designed for both time and position determination and is currently (2002) the best system for time transfer.  See my Time and Frequency web page for more on time

Surverying has to do with determining positions on Earth. Many aspects of astronomy have a strong relation to time and position.


Once you know where you are, you still need to know in what direction lies your goal.  Even today with a GPS receiver that tells your position, you still need a compass to determine direction.  You can deterine diretion with GPS by taking a reading then moving to another location and computing the direction you traveled, but the GPS receiver when at rest does not provide any bearing information.


One of the classical uses of gyroscopes is in aircraft instruments and control systems.  The first inertial navigation systems used gyroscopic stabalized platforms and today modern filght control systems also use gyroscopes.  In all these cases the gyroscope is used for relativly short times.

A gyroscope can also be used to determine true North.  For example a surveyor inside a cave can use a North finding instrument that does not depend on sighting the Sun or stars yet produces a very precise horizontal angle "fix". The AG8 is the military nomenclature for one of these systems.


Inertial navigation depends on Sensors for orientation.  A classical system uses a three degree of freedom gyroscopic platform with accelerometers in each axis.  More modern systems use strap down fiber optic laser gyros.  The problem is drift.  If an inertial system is just placed in a static location and the position plotted for some time it will drift.  That means that the precision of the "fix" gets poorer and poorer as time goes by.  Inertial systems need periodic updates using some other method.  The Transit satellite navigation system was designed so Polaris subs could update their inertial nav system.

These systems are typically large and expensive and so you'll find then on large high value vehicles although I have seen that the military has a system that can be mounted in a jeep.





This is a very high quality compass and inclinometer.  There are two versions of the dial, one is in degrees and the other is in Mils.  Which is the military degree measurement used for artillery, it is equivalent to 1 yard at a range of 1,000 yards.  For most compass uses the degree version is much more useful, but all the military M2 compasses are in Mils.  Mils may be short for milli radians.

Although you can still buy this from Brunton in a number of different sizes it was origionally patented by Brunton 526021 , 1062582 , 1092822 and later a version was patented by K&E 1571697   Transit Feb 2 1926.
There are a large number of replica "Brass" versions now for sale, who knows if they are even functional.
The M2 was/is used to setup artillery, mortar and other sites where you need a good magnetic bearing and also for rough field survey work.


Sperry Creagh Osborne Marching Compass MKVII  Mod. E

MC-1 Magnetic Compass Flight line Calibration Set

Works with 400 Hz "Y" connected synchro type sensors and indicators as used in aircraft.


The surveying transit evolved from a compass coupled to a telescope.  Almost all transits have a compass built in so that magnetic North can be indicated and true North can then be determined.

Wrist Computer

Vector by Suunto - contains clock with time, date, alarms, magnetic compass, barametric pressure & altitude as well as temperature.

3 Axis Earth's Field

info wanted on this unit



By manually signting a star or the Sun the direction of true North can be determined.  This instrument was typically used in aircraft and was held in a "bubble"aka dome  requiring the optical distortion effects of the bubble to be corrected.

Periscopic Sextant

The periscope was mounted in a hole in the top of the plane and was out in the outside air.  It thus did not require any "bubble" correction and was much easier to use.

Automatic Astro-Compass

This unit has a star tracker assembly with its own glass "bubble" and is pressurized, probably with dry Nitrogen, to prevent fogging of the optics.  It has a larger prisim at the objective end than the periscopic sextant, probably to gather more light for the photomultiplier tubes that detect the star.  This model may not be able to track start in the daytime, but later version could.

Transit Surveying Instruments

For centuries surveyors have used the Sun and stars to determine true North.  To do this there are attachments for transits to allow imaging the Sun without damage to the users eye(s).

Leitz 115A Engineers Transit  uses the older 3½" x 8 thread tripod

K&E Hand Level

This is a very early square tube unit with no optics except for a first surface mirror to view the bubble from the bottom.  I think is was build is such a way as to avoid the Locke patent 7477 hand level that K&E later offered after the patent ran out.

T. F. Randolph Level

Compact tripod mounted leveling scope with cross hairs and spirit level, with 1884 patent 297164 date. In a patented seamless leather box.


These instruments are similar to a surveyors transit except instead of mounting on a tripod they are held by a ruler.  There is no horizontal angle measuring ability, instead a ruler parallel to the line os sight is used to draw a line on the map directly in the field.  The method of Stadia is used to determine the distance to the rod.  This was the primary tool used in the U.S. to make topo maps for many years.

K&E 76 0000 Alidade - self indexing (auto leveling) and built in trig for horizontal and vertical distance based on stadia reading.

Abram's Sun Compass

This is a Sundial that has been designed to find North when the time and location is known. It will work when mounted on vehicles and tanks whose ferrous metal content renders a normal magnetic compass useless. eBay photo
Nice web page covering the Sun Compass and other Field Navigation devices
TM5-9422 Compass Universal type Abrams SC-1

Dent Meridian Instrument - Dipleidscope

Used to establish the time of meridian passage of the Sun or a star.

Chinese Sun Dial and Compass

Sextant, Aircraft



A-10A Bubble sextant used by Army Air corps Navigator in B25s during WW2


The Sun has been used to find compass directions back as far as recorded history.  There are many way this can be done with a considerable variation in the precision of the resulting "fix".  See also my Sundials web page.

Pilot Balloon Observation (Pibal) Theodolites (mirror web site)

These theodolites are used to track baloons as they rise for learning about the speed and direction of the winds aloft.

Stellar Time Keeping

Similar in concept to the Automatic Astro Compass, but instead of tracking a single known star a scanner looks at the star field and figures out either where it is or what time it is.  Was looking for information on the Danjon Astrolabe, but so far have not found any info on how it works.



This was a system operating in the frequency range around 10 to 15 kHz.  Ships at sea could keep track of their position in a "lane" defined by the phase of the signal.  System became obsolete with the deployment of GPS.


Radio Receiving Set AN/TRQ-23

Army field set for getting DF bearings covering the HF, VHF and UHF frequency ranges.  Uses antennas rotating up to 150 RPM and a CRT display.  Will provide a bearing even with a very short transmission.


38 - 55.4 MHz DF Loop Antenna


This is an H.F. radio receiver with a loop and sense vertical antenna system designed to determine the bearing to a station.

Non Directional Beacons

These are located on or near airports and send a carrier and single sideband CW ID in the 200 to 400 kHz range.  Aircraft can tune into the carrier and get an indication of the bearing to the station.


Very similar to the ARN-89.
ARM-93 Test set.
LF Automatic Radio Direction Finder Set; manufactured by Collins; used in A-37, C-2, UH-1, AH-1T, VH-3A, OH-6, P-3, S-3, OV-10, U-8F, U-21A


Vietnam era helicopter 100 to 3,000 kHz frequency coverage direction finding receiver. can use NDB, AM broadcast stations or other signals in this requency range.

Light Weight Beacon

Viet Nam era. Transmits a programmable ID on a frequency in the 265 to 535 kHz range and includes a 50 foot antenna with no part longer than 19 inches.  The complete system is in one back pack.  Most likley made for use with the ARN-89.


The post W.W.II Loran-A system operated around 1.8 MHz was replaced with the Loran-C system operating with pulsed signals on 100 kHz.  Maybe Loran-B was an idea that never was made operational?  There are a number of "chains" consisting of 3 to 5 stations with all the stations in a chain using the same Group Repetition Interval (GRI).   If a scope is triggered from a GRI generator the stations is that chain will appear as pulses with different fixed times on the horizontal axis while the pulses from stations using other GRI values will be jumping around.  Until GPS this was the most accurate system for positioning and for time transfer. 
2005 - It looks like Loran-C will be used for aviation safety providing a redundant system to support automatic landings.  Other systems like the Russian or European equivalent to GPS are not good candidates because a jammer for GPS would also take them out.

Table of Loarn-C Chain Stations -

Loran Patents 

Micrologic SportNav with MGRS

This hand held unit was for use in the Operation Desert Storm/Shield area by the U.S. military.


This is designed to attach to either a PRC-25 or PRC-77 back pack VHF low band transmitter receiver and report position via radio.  Also receives Loran-D which must be a temporary system that the military could put in place.
Austron 2100F LORAN-C Frequency Monitor - for precise Frequency
Austron 2100T LORAN-C Timing Receiver - for precise time
Austron 2042 LORAN-C Simulator -
Lorchron LORAN-C Timing Receiver LFT-504 - for precise timing
TI 9100 Aircraft Receiver


When Sputnik was launched in 1962 the doppler signal was used by scientists at Princeton to determine the orbital parameters of the satellite.  They quickley realized that if a satellite was to transmit its orbital parameters then a person on the Earth could determine their position.  This was the basis for the Transit Satellite Navigation System.


There were only a small number of satellites transmitting on 150 and 400 MHz.  A submarine whose inertial navigation system had drifted could receive the Transit pass which took maybe 15 to 30 minutes and then update their inertial system.  This system required a very high quality = expensive (atomic) clock.  When the GPS system was being developed one of the parameters was to eliminate the need for an expensive clock.
A 120 to 170 MHz eggbeater antenna would allow reception of the Transit signal on a vehicle.
MX 4102 Satellite Navigation receiver by Magnavox


The GPS system has about 24 satellites in medium orbits (they are lower than geostationary) orbiting the Earth in three rings.
They transmit their orbital parameters.  By receiving the signals from four satellites a GPS receiver can figure out where it is and also the error in its clock.  If the receiver is in a known location only one GPS satellite is needed to know the time.  If more than 4 satellites are received the quality of the position fix imporves.  It may be that 1/2 of the satellites are visable at a time and that's why there are twelve channel receivers.

Stanford Telecom 5001A Navstar Test Transmitter

In order to test GPS receivers before any satellites were in orbit, Stanford Telecomunications built a small number of GPS transmitters.  They later made custom chips for military GPS receivers.
I have heard from a former STI imployee that these receivers were used to debug the large scale ICs STI made for GPS receivers.  In particular channel to channel timing skew.
AN/URN-502 Canadian Military GPS
This, large by today's standards, GPS receiver was built using different printed circuit boards for different functions and an OEM GPS receiver board made in Japan.

Quantic Q5200/SM

This GPS Timing receiver was designed for military GPS timing and uses a couple of the Stanford Telecomunications GPS chips.  Needs a down converting antenna, if you know about the antenna, please let me know.
Garmin GPS III+
This hand held 12 channel GPS unit has a built in World map and bread crumb trail capability.  It can also average Lat and Lon but NOT altitude, mine is up to 3,051,294 averages today, and can go to 99,999,999.  This will taks some time becasue the readings are one per second. It took about 35 days to get this far. I would take over 3 years to run out the counter.
Motorola GPS Oncore VP
These are 8 channel general purpose OEM receiver boards that I have in the evaluation version boxes.  They have timing accuracy in the 30 nS area when used in the known position mode where all the variables are applied to getting a good 1 Pulse Per Second.  Unfortunately they have been discontinued and there is not a replacement with the same verycomprehensive capability. Synergy is where I purchased my VP+ units.
Motorola M12+ Timing
If the M12 has the same Motorola binary format differential correction output that is in the VP series (I most probably does) then it should be possible to place the antenna at a know location and using some math save the corrections for each satellite.  Then switch to rover mode and have those same corrections fed back into the receiver to correct it.  This is covered in a CSI patent, but they don't offer it in this format.  Note this is much different than "poor man's differential correction" since actual corrections are being made for each satellite, not just a Lat and Lon position correction.  The key limitation is the time from obtaining the differential correction and the time that most of the satellites set.  Note that GPS sats have a nominal 12 hour orbit so maybe 4 hours overhead.

PLGR Family

 - follow on after the Trimpacks, is a large hand held unit.

Trimpack Family

p/n 14992-20 & 16768-20 AN/PSN-10 SLGR, Came out just in time for Desert Storm & Desert Shield, gulf wars.  Since these were L1 CA code receivers L1 was turned off for the Gulf wars, Desert Storm and Desert Shield.  Many of these can average Lat, Lon and altitude

GSM-336 GPS Test Set

 (@BPB Surplus) Anyone have info on what this set does?
 TM 11-4920-297-12 Opertion and Maintenance Intermediate for
Navigation Set Test AN/GSM-336(V)1, 685-7539-001, (NSN 6625-01-319-7118),
Navigation Test Set AN/GSM-336(V)2, 685-7540-001, (6625-01-294-1941),
Navigation Test Set AN/GSM-336(V)3, 685-7541-001, (6625-01-317-4851)
 {TO 33D7-71-51-1; NAVAIR 16-30GSM336-1}

TM 11-4920-297-12P Illustrated Parts Breakdown for
Navigation Test Set AN/GSM- (NSN 6625-01-319-7118), 685-7539-001,
Navigation Test Set AN/GSM-336(V)2, (6625-01-294-1941), 685-7540-001,
Navigation Test Set AN/GSM-336(V)4, (6625-01-347-1757), 685-7540-020,
Navigation Test Set AN/GSM-336(V)3, (6625-01-317-4851), 685-7541-001
{TO 33D7-71-51-4; NAVAIR 16-30GSM336-2}


Surveying Patents -
Army Space Reference Text - 7-26  Characteristics of an Ideal Pos/Nav System -
" - same thing at FAS with proper formatting
Navigation mailing list -
American Society for Photogrammetry & Remote Sensing - Grids & Datums -
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