ę Brooke Clarke 2005 - 2023

Uncle & Grandfather
North Finding
Electronic Levels
HP-48 Graphic Calculator
Earth's Dimensions
    On line Photo Maps
Surveying Patents - separate web page
Total Stations
Surveying Patents
Scanned Books & Manuals
My Related Web Pages

Uncle & Grandfather

My grandfather on my mother's side was a land grading contractor.  He used horse drawn equipment.  His son (my uncle) was also in the same business but he used modern heavy equipment.  The Huber-Warco grader had hydraulic controls, most of which had been welded because the "cat skinners" that he hired were trained on the Caterpillar version that had mechanical dog clutches and if you didn't hit them hard you might get a broken wrist.  His Euclid bucket (Wiki) had an engine in front and another engine in the back.  His competition was using CAT scrapers and a bulldozer to push the scraper.  That means his competition had to hire two heavy equipment operators and my uncle only hired Sid.  Both very modern machines for the early 1960's.

I have my grandfather's level & tripod.  It only has a scope and level bubble attached to the scope.  Not angle readouts.

My uncle had a good "eye for level".  He also carried a hand level and a yard long lath with a notch for the hand level on various tractors.


 I use the method called Stadia to determine both the distance and elevation from the instrument to the rod.

An <shift><click to download> Excel spreadsheet does the math.  The Example Spreadsheet has an explanation of how to use it.

I got my own Leitz 115A transit.

I tried using the Bushnell golfing range finding binoculars, but they only have 1 yard resolution and I am trying to get to ideally inches, but practically to feet of accuracy, so they don't work well.

Stadia is part of Plane Table mapping using an alidade.  See M1913 Sketch Set.
POB magazine - Plane Table Mapping -


I use drafting software to plot my boundary and the adjacent neighbors boundary based on the county recorded maps.  This is for the purpose of doing the landscape design, not for the boundary.  I have found all but one of the survey markers on my property border.  These form the basis for the contour map.  The house is shown, but now I am trying to locate wooden stakes so that I can then draw the elevation contour lines.

North Finding (separate web page)


A gyroscope will precess and this can be used to determine true North.  It finds use in underground locations where you can not sight the North star Polaris or the Sun.
See my Sensors page North Finding for more on this.
The government version is called the AG8 and is covered in TM 5-6675-250-10
The theodolite is the T16 and is marked:
p/o (part of) GG3-1 North Seeking Gyroscope
NSN 6675-01-289-8481
p/n 560 247

1999 Sun and Polaris Ephemerii

By sighting the Sun or North star you can determine the direction of true North very accurately.  To use this method you need to know either where the Sun is or know where the North star is.  That is why the Ephemeris data is required.  Without it you can get to within a degree or so, but with it you can get to seconds of angle.
the Advantages of Polaris Observations in  Land Surveying - Night or DAY


The later versions of the PLGR and all the DAGR GPS receivers have a North Finding function (the DAGR calls it Gun Laying System).  There are two methods, one uses a single GPS receiver and the other uses two GPS receivers.  They replace the AG8 in most applications providing the same accuracy for a lot less money, volume and weight.

Electronic Levels

US5537201: Electronic leveling system, electronic leveling apparatus and leveling staff by TOPCON  DL-100 Series Digital Levels - Article in Prof Surveyor - June 99
The rod has a special pattern that can be read by the level.  The height and distance to the rod can be automatically calculated.  The rod may have correction for tilt and temperature.  Topcon does not really tell you what their equipment can do, maybe all surveyors already know.

HP-48 Graphic Calculator

This calculator has an RS-232 port and some of it's many uses is as a data collector and doing surveying calculations. - HP48 & HP28 Information

Surveying Application

Tripod Data Systems, Inc. -
Chris Nail - some programs for download
Apex Data Collection Software - 30 free trial
J.S.  Sprott Programs - - programs for a lot of applications
CalcPro - many bugs on new web pages
Quickclose - Uploadable and editable ASCII HP48 programs -

New HP49G Calculator

Earth's Dimensions

Radius (Wiki) : 6,371 kilometers (3,959 mi)
Figure of the Earth (Wiki)
Polar motion (Wiki)
Chandler wobble (Wiki)
Nutation (Wiki)
Axial precession (Wiki) - precession of the equinoxes
International Latitude Observatory (Wiki) - my local (Ukiah, California) Latitude Observatory
Richard Feynman: Messenger Series Lectures on Gravity


On line Photo Maps

Microsoft Terra Server - input a City name and see a composite aerial photo
Google Maps - allow Lat Lon input or street address + you can overlay the street map and photos 1 meter sat photos
and there's a new one that escapes me today, maybe at Microsoft

LAND INFO International - sold in packages
TIGER Mapping Service - U.S. Bureau of the Census
Multiresolution Seamless Image Database (MrSID) - U.S. Geological Survey Bay Area DOQ Imagery - variable resolution on line map
USGS - National Mapping Information - Aerial Photographs - Digital Orthophoto Quadrangles - USGS Global Land Information System -
Microsoft Terra Server - input a City name and see a composite aerial photo
Chinese Embassy in Belgrade (NIMA #M903), Marine pilot cuts down gondola cable, military choppers hit power lines - in all cases people died because of bad maps by NIMA? or maybe a cover up to destroy B2 parts in the embassy
USGS - Digital maps, databases, book-type reports, fact sheets, computer programs, and other products - Thematic maps are maps that display specific types of information (themes),  such as geologic maps, maps showing concentrations of particular minerals or  elements, earthquake or landslide hazard maps, etc.
USGS - US Geo Data - not web viewable - requires Public Domain Software for use with GeoData -
Map Express Inc.  -
Topo Zone - on line 7.5' quad maps

mapONE -


The eBay listings for survey instruments typically have very wrong titles.  Here is what I think these things are: Heliotrope - Uses mirrors to send the Sun's rays to a far away surveyor so he can take a reading on the location of the Heliotrope.  Photo from Transits of Venus - another heliotrope

From: Transits of Venus
Illustration from The principles and Practice of Surveying Vol II
Steinheil Heliotrope
Steinheil Heliotrope Function diagram

The "telescope" on the back does not have an eyepiece, but instead has some white material that reflects the sun back.  This causes a reflection on the clear glass center spot and when that image of the sun is pointing to the target, the sun is reflecting at the target.

This is very similar to the way a survival/rescue mirror works.
On heliographs one way of doing this is to have both sides of the mirror silvered.  Then when your eye seen the sun's image on your face or clothing centered on the hole that allowed the sun's light to make the image, you are looking at where the sun will be reflected at a great distance.  This method is as accurate as the front mirror is parallel to the rear mirror.

ESSCo Heliostat
A mirror that turns to de-spin the Earth and send the Sun's light to some fixed point.
Wild T4 Theodolite
I think this is the most accurate of all the surveying instruments.  (they go for about $35,000 used on eBay)
TM 5-6675-297-15  <- survey squadron   <- survey squadroni

My Instruments

If you know where this level vial is used please let me know.

Survey Signal Lamp 2 Inch

Got this after studying the M-132 Signal Lamp.  The M-132 is a mystery since it has a lot of features that do not make sense on a Morse Code signal lamp, but do make sense on a survey instrument.  This Survey Signal Lamp has very similar features, i.e. a peep sight, up-down tilt mechanism, azimuth pointing by rotating about the mounting screw (either 1/4-20 or 5/8-11)


Light, Signal, Survey, 1 In, Diameter
Reflector, Battery pwd., w/case size 1
FSN 6675-641-3536 (FSN 6675-641-3569 is for a Wallace & Tinnerman altimeter)
Stewart-Thomas Industries, Inc.
Contract DSA 700-69-C-G140
Serial No. xxx Del'd 1970

Looks like New Old Stock (NOS).  There is no serial number on the label.  The lamp bags contain both PR2 and PR9 Flange type flashlight bulbs.  The PR2 is brighter and does not last as long as the PR9.
PR22.38 Volt - 0.50 Amp - B-3-1/2 Single Contact Miniature Flanged Base (P13.5S) - C-2R Filament Design - 0.80 MSCP. - 15 Average Rated Hours - 1.25" Maximum Overall Length - 0.45" Maximum Overall Diameter - Typically found in flashlights using two "D" cell batteries.

PR9: Standard replacement flashlight bulb - 2.70 Volt - 0.15 Amp - B-3-1/2 Single Contact Miniature Flanged Base (P13.5S) - C-2R Filament Design - 0.25 MSCP. - 45 Average Rated Hours - 1.25" Maximum Overall Length - 0.45" Maximum Overall Diameter - Typically found in flashlights using two "D" cell batteries.

Power can be supplies via field wire using the push down terminals or by a cord with phone tips.
There is a knob on the back that tilts the lamp head up or down.  Azimuth aiming by rotating about the mounting screw.

It occured to me that this would be an excellent way to mount the RA-2 GPS antenna using the magnetic feet on the antenna.  This is because the Signal Lamp has both 1/4-20 and 5/8-11 threads.  BUT . . . the sheet metal is aluminum so it does not work.

Fig 1
                  Signal Lamp 2 Inch
Fig 2
                  Signal Lamp 2 Inch
Fig 3
                  Signal Lamp 2 Inch
Fig 4
                  Signal Lamp 2 Inch
Fig 5
                  Signal Lamp 2 Inch

Surveying Patents


In high school I took all the drafting classes that were offered.  Later that became important since it was a prerequisit to taking a Physics class at Foothill College that allowed me to get an AA degree in 1962, then a BSEE in 1964 and MSEE in 1965.  Without the drafting class those dates would have moved back a semester or year.

Polar Planimeter

The Planimeter (Wiki) is a drafting tool used to measure an area by tracing out it's outline. The early models are analog computers.
2768785 Planimeter, Ernest W Silvertooth, Librascope , 1956-10-30, -

Scanned Books & Manuals

I have scanned a number of books and manuals relating to surveying instruments see:

Total Stations

Pentax - total stations, etc.
Leica - total stations, etc.
Sokkia - total stations, etc.
Cyra - 3D laser scanner $155,000
Nikon - total stations, etc.
Spectra Precision - total stations, etc.
Topcon -  total stations, etc.
Trimble - GPS but also total stations

My Related Web Pages

Navigation, Orientation, Position
Sundial Patents
Flashlight Patents & Photos
Electro-optical Gadgets
Time & Frequency
Stellar Time


Ref 1. YouTube: How do trig points actually work?, 15:03 -

1. Error caused by thickness of metal strap inserted into trig pillar side plate.
2. Error when using mag compass to take bearing since no declination correction.  Much better to measure angles T1 to Tn and T2 to Tn.


Allen Precision Equipment - dealer in surveying supplies -
Anderson Instrument & Supply Co. - manuals -
Berntsen Survey Markers -
Chicago Steel Tape (CST) - equipment manufacturer - good prices - Berger DGT-20 Transit - very reasonable price
Collection of Scientific Objects - Photos - - carries CST/Berger DGT20
Department of Natural Resources and Environment in Victoria, Australia - Geodesy in Victoria - Cadastral Surveying -
Engineering Equipment  -
The Dividing Engine in History -
EM 1110-1-1003 - Engineering and Design - NAVSTAR Global Positioning System Surveying
FM 6-2 Tactics, Techniques, and Procedures for FIELD ARTILLERY SURVEY - Army Field Manual
LO Ink Specialties - Hard to Find stuff
POB -Point Of Beginning - magazine
Professional Surveyor - magazine with good articles and advertizers & annual "Source Book" - resource including classified ads
Servco - old and new Leica/Wild equipment -
sci.engr.surveying - newsgroup Archive -
SECO - hand levels & supplies
SubSurface Instruments , Inc. - Magnetic, pipe leak, cable
Tripod Data Systems - now -> Spectra Precision
Univ. of Portsmith dept of Civil Eng  - Surveying - all kinds of stuff

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