Alidade Plane Table Surveying Instruments

& AG8 North Finding System

Brooke Clarke, N6GCE

Photos from eBay with links to the auction
Brass Reproduction Alidades
Marine Alidades
Surveying Patents - moved to seperate web page
Alidade Patents
Alidade Manuals
AG8 North Finding System
GG3-1 North Gyroscope


1. An indicator or a sighting apparatus on a plane table, used in angular measurement.
2. A topographic surveying and mapping instrument used for determining directions, consisting of a telescope and attached parts.

There are a number of common usage's, the main subject of this web page is the map making surveying instrument used on a table that has been leveled.  On ships an Alidade is used to measure the angle from the ship's longitudinal axis to some target or targets, typically to help determine the ships position relative to the target(s).  Large telescopes have an alidade system that's used to point in azimuth.

These were used on a wooden table that had a drawing attached.  The idea was to make a map while in the field using stadia for distance to the rod.


K&E 5093A Scale

In this close up photo of the K&E 5093A Scale you can see that when the alidade is level the Lower center vernier will read 30 degrees, not zero.  This is to avoid blunders which probably were common if level was 0 and there were + and -  numbers on both sides of 0 where a sign error would be a blunder.  Vertical angles from -30 deg to +30 deg can be read as 0 to 60 deg.  That is the limit of vertical angle measurements, since the rest of the scale is used for the horizontal and vertical distance factors.

On the left is the "HOR" vernier and on the right the "VERT" vernier.  These are used to convert the slant distance measured using the stadia method into horizontal and vertical distances.  When the alidade is level the HOR correction reads 100% and the vertical correction reads 50% (note you need to subtract 50 from the VERT reading to get the correction factor that's multiplied times the slant distance.

Notice that when the alidade is level all three readings are very much different.  Again, I'm sure this is to aviod blunders.


plane table surveying - is a good search phrase
Article in Point Of Beginning "Plane Table Mapping" -
Penmap Digital Plane Table -
Instruments of Science and Technology - The Plane Table -
Doug's Amateur Surveying Page - links to some plane table references
Elements of surveying and surveying equipment - Ch 11 -   Plane Table -
Comparison of surveying techniques -
Surveyor's Plane Table - offered new for sale in the UK, and a very simple alidade.
F.W. Breithaupt & Sohn - Topographical Instruments -
Surveying Historical people & dates -


This is a collection of Alidade surveying  instruments from eBay.

1800s Brass

eBay -




eBay reserve not met, relisted  eBay

1951.C.T.I MFG CO.LTD.



Might have stadia computation on vernier?

Compass with square scale

6220 (12 to 24 Power) & 6230 (10 to 18 Power)

no photo yet


Cat. No. 508  has "H" scale
18x24" w/Johnson tripod head  eBay



Teledyne Gurley No. 582
The has "H" & "V" Scales, eBay -

Teledyne Gurley No. 582



Models with the suffix "SA" have a stadia arc.


Three versions:
5096A - 11 3/4# rigid
5096B - 14 # rigid
5096C - 9# extension legs

Drawing Boards

5096-1 is 15" x 15"
5096-2 is 18" x 18"
5096-3 is 18" x 24"
5096-4 is ?
5096-5 is 24" x 31"
Mk II non optical Alidade
        non optical Alidade
1800 or early 1900s

No. 5093A called the Geological Survey Alidade weight 7#

No 5095A called the Expedition Alidade (more compact design), weight 5 #

63886  1935
eBay - photob, photoc, photod, photoe  -

119029 might be a model 76 0030

Military model
eBay -

eBay, eBay
Model: 5093A eBay

   Model 53491 eBay

K&E 76-0000

76 0000

Samll photo of K&E 76
            0000 eBay
eBay, another similar by ponejail, eBay



Lutz EX-3

Photoa, Photoc, eBay

1917 Ottway Ealing No 92


SAN (Chinese)

E-3 eBay looks like a copy of the C.T.I (above)

MA-5 MOM of Budapest Hungary

MA-5 Hurgarian
          AlidadeSimilar to the Watts, but not an exact copy or even a completely different design.
Uses optical scales rather than a mechanical scale and vernier.





eBay Item 729809183 -

Plumbing Arm on Plane Table Case

eBay -


Has a protractor that fits onto their 5007 and 5008 Com-Pro Pocket Transit for map making
Note there are a number of different Brunton pocket transits in different sizes and mad form different materials.
Also the military versions are have graduations in "mils" not degrees.

Brass Reproduction

Fraud Aleart

eBay - tedamar

Repro at Yahoo Shops

Canyon Gold  -

Short Repro


Atlas Instruments -

Surveyors Plane Table -


National Museum of American history - Alidade - links to a number of instruments and long list a makers & their history

National Geodetic Survey - no instrument data

Antique Surveying Equipment - many instruments for sale:

Hilger & Watts 6200

1944 Gurley

Gurley 580

Dietzgen 6250

Mapping with a Plane Table and Alidade - instructions for use

Photos of field use -

NOAA Photo Library - drawing of an 1820 instrument - photo over water - 1894 instrument -

Stadia problem set as pdf document and another worked example -

Humboldt State University - Instrument Collection - Alidade-

Plane table - diagram of tripod to plane table connection, to accomadate leveling the table

Traditional alidade instruments combined with a Sokkia SET500 TS -

Plane table, alidade, and wye level - as a set.  Mentiones: A metal hinged plumbing arm to position the pointer and plum bob at any location on the plane table.

Instruments of Science and Technology - Plane Table Alidade. circa 1725 - Plane Table Alidade circa 1820 -

Photo of under side of 1840 table and French manuscript -

Finding the Way and Fixing the Boundary -

Alidade Patents

These numbers from a Dietzgen Alidade Model 6230:

D98679 Design for a transit support, Adolph Langsner Eugene Dietzgen Company, Feb 25, 1936
D98680 Design for a transit plate, Adolph Langsner Eugene Dietzgen Company, Feb 25, 1936
D98681 Design for a dumpy level, Adolph Langsner Eugene Dietzgen Company, Feb 25, 1936
D98682 Design for a Y level, Adolph Langsner Eugene Dietzgen Company, Feb 25, 1936
2053837 Stadia instrument, Adolph Langsner Eugene Dietzgen Company, Sep 8, 1936, 33/284, D10/66 -
2101077 Spirit level and mounting, Adolph Langsner Eugene Dietzgen Company, Dec 7, 1937, 33/386 -
2102364 Spirit level and means for mounting same, Langsner Adolph Dietzgen Eugene Co, Dec 14, 1937, 33/385
2126195 (Alidale) Sighting device and support for same, Adolph Langsner Dietzgen Co Eugene, Aug 9, 1938, 33/282, 33/333
2126335 Telescope, Langsner Adolph, Dietzgen Eugene Co, Aug 9, 1938, 359/513 -
2127302 Level, Langsner Adolph Dietzgen Eugene Co, Aug 16, 1938, 248/181.1
2130095 Telescope, Langsner Adolph Dietzgen Eugene Co, Sep 13, 1938, 359/513, 359/426, 359/823 -
2132170 Transit, Langsner Adolph Dietzgen Eugene Co, Oct 4, 1938, 33/299, 24/265.00B -
2132171 (Alidale) Surveying instrument, Langsner Adolph Dietzgen Eugene Co, Oct 4, 1938, 33/282 -
2132172 Tangent adjusting means, Langsner Adolph Dietzgen Eugene Co, Oct 4, 1938, 33/299, 248/180.1
2171755 Actuating mechanism, Langsner Adolph Dietzgen Eugene Co, Sep 5, 1939, 33/349, 33/355.00R -


U.S. Army TM 5-6675-211-15P - Dietzgen 6230 (10 to 18 power) & 6220 (12 to 24 power)

AG8 North Finding System

This is a gyroscope based instrument that finds true North.  Used by the military for artillery and for surveying in caves where much more accuracy is needed than can be had with a magnetic compass (or the compass does not work because of the location).

These are parts of a North Finding system, but maybe not the AG8.
ARK2 Gyroscope (or ARK1 or GAK1?)
GKK3 DC - AC Converter
GKB2 Battery
GKL3 Batt. Charger
GST10-2 Tripod
Kern _____ theodolite

Wild GAK1 Gyroscopic
                  North Finder crosssection

The CERN Applied Geodesy Group developed an automatic gyroscope, based on the Wild GAK-1,
by replacing the graduated scale by a CCD line of 1024 photodiodes, and the manual adjustment
knob by a motor encoder, to achieve computer-controlled release of the spinning motor.
(from: Engineering Surveying Technology by T.J.M Kennie, G. Petrie, ISBN: 0751401935, 0-203-86074-8)

Some of the later PLGR GPS receivers and all of the DAGR GPS receivers have a "Gun Laying System" (aka North Finding) that is as accurate as the AG8, cost much less and can be held easily in one hand.  But will not work inside a tunnel, so there's still some need for the AG8.  The method depends on carrier phase tracking which is much more accurate than differential correction.

Kern DKM1
eBay not working
Note that it's possible to use two GPS fixes to determine North with high accuracy.  This can be done using two interconnected GPS receivers, like the PLGR or by using a single receiver like the DAGR.
The method may be similar to Differential Corrections, i.e. if the master GPS location is known (or determined by averaging) then range and range rate errors for each satellite can be determined and used to correct the slave GPS receiver.  Another method involves using carrier phase measurements and resolving the interger errors leading to cm accuracy.

GG3-1 North Gyroscope

NSN: 6675-01-289-8481

Uses the Wild Heerbrugg T16 Theodolite PN 560247.  But that part number does not include the gyroscope.


Spy Mission to Montana - CIA mission to locate missle silows using Alidade and Plane Table as well as a Burton Compass.  The compass was tripod mounted and used to measure bearing angles (not compass directions) between the power pole at the missle site and some landmark, like the road.

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