Equipment Care and Maintenance

Chris Rotegard, Leica Geosystems Inc.Rosemount, MN

2012 MSPS Conference

Accuracy & PrecisionOverviewIntroduction

Principles of Survey Revision

Classification of Errors

Instrument Care

EDM Types

Angle Reading Types

ATR

Specifications

Who is Chris Rotegard?

Mr. Rotegard has been serving the surveying and engineering community for 25 years. He started his career at Brunson Instruments as a Service Technician. After 7 years he entered the Sales division with Sokkia Corporation working to the

position of District Manager. After a brief time with Fieldworks he is employed by Leica Geosystems

as a Direct Manufacture Representative. Mr. Rotegard is a certified Instructor in GPS, Robotics

Technology as well as Data Collection.

A heritage of trust …a history of getting it right

180 years of Measurement Technology

2005 Acquistion by Hexagon2004 Divestment Swiss Optics and Escatec

Acquisition Tritronics2002 Divestment Vectronix (defense)2001 Acquisition Cyra, Acquisition Laser Alignment

Acquisition ERDAS, Acquisition LH Systems2000 IPO at Swiss Exchange (SWX)

1997 Leica Geosystems1994 Acquisition GPS-Magnavox (US)1990 Merger of Wild-Leitz and Cambridge Instr into Leica1988 Acquisition Kern, Aarau1986 Merger of Wild and Leitz into Wild-Leitz1921 Wild founded in Heerbrugg, Switzerland1819 Kern founded in Aarau, Switzerland

Milestones in Technology

� 1923 T2 First modern theodolite� 1944 T4 Optical theodolite w/ accuracy to .0.01 second� 1950 First removable tribrach – Now a standard!� 1968 DI10 First theodolite mounted EDM� 1973 DI3 First instrument mounted EDM w/ slope

reduction� 1977 DI4 First compact EDM w/ on-board coordinate

computation� 1979 TC1 First all electronic total station w/ on-board data

collection� 1983 T2000 First 0.5” electronic theodolite w/ 1st order

trigonometric leveling

Milestones in Technology (cont.)

� 1985 WM101 First GPS receiver designed specifically for surveying applications

� 1985 DIOR First reflectorless EDM w/ geodetic accuracy� 1987 GRM10 First palm sized data collector� 1990 NA2000 First electronic digital level� 1992 First all on the pole GPS� 1995 360 degree prism� 2004 System First totally fully integrated TPS / GPS surveying

1200 system� 2005 First total station with integrated GPS

Principles of SurveyError classification

� Random – Always small – Reduced by Field Procedures

� vary in sign and magnitude.

� Constant – Prism offset

� same sign and same magnitude.

� Systematic – Incorrect Tape calibration / EDM corrections

� same sign and varying magnitude.

� Periodic – Graduation errors on an instrument Hz or Va plate

� Vary in sign and magnitude

� Blunders – Should never happen!

Accuracy & PrecisionDefinitionAccuracy – The ability to get as close as possible to the true value. The ability to measure the correct value.

Precision – The ability of the operator/operation/equipment to repeat over and over the same routine. The ability to measure within close tolerances.

Accurate Precise Accurate & Precise

Accuracy & PrecisionOne Measurement Only

� One reading – no redundancy� Single reading proves nothing!

Accuracy & PrecisionNot Accurate – Not Precise

� Poor instrument� Poor field procedures

Accuracy & PrecisionNot Accurate – Precise

� Good instrument� Poor field procedures

Accuracy & PrecisionAccurate – Not Precise

� Poor instrument� Good field procedures

Accuracy & PrecisionAccurate - Precise

� Good instrument� Good field procedures

(Fig. 1) One reading only, no redundancy

(Fig. 2) Poor instrument, poor method

(Fig. 3) Good instrument, poor method

(Fig. 4) Poor instrument, good method

(Fig. 5) Good instrument, good method

(Fig. 1) (Fig. 2) (Fig. 3)

(Fig. 4) (Fig. 5)

Accuracy & PrecisionSummary

Sources Of ErrorErrorSome Practical Sources & Limitations

� Manipulation� Incorrect procedure� Transpose figures� Mathematical errors� Fraud

� Personal Limitation� Resolution of eyes� Ability to operate� Manual operations

� Instrument Limiatations� Stability of construction� Stability of support� Telescope resolution� Least count

� Environmental Limitations� Business� Human� Instrument� Atmospheric

Care and maintenance

TripodsDo yours pass the test?

� Setup and level the instrument. Point to a well defined target over 500 ft away

� Twist the tripod head both ways and sight

� If the horizontal angle changes after sighting on the target again, the tripod needs to be adjusted, repaired or replaced

Tripod Head

Dowels (Rounds)

Shoes

Clamps

Hinges

TripodsCritical areas of concern

TripodsAdjustment� The connections between

timber and metal must be firm and tight.

� Moderately tighten the allen screws (1) with the allen key supplied with the tripod.

� Tighten articulated joints just enough to keep the tripod legs open when lifting the tripod of the ground (2).

� Tighten the allen screws of the tripod legs (3).

TripodsUse and care� Loosen screws of tripod legs,

pull out to required length and tighten

� When pressing the legs into the ground, the force should be applied along legs

� The tripod is for the instrument, it is not a hammer

� Store the tripod properly in your vehicle

TribrachThe foundation of any instrument

� Must be maintained� Adjustment is simple

� Check w/ adjustment ring� Check w/ plumb bob� Use instrument w/ electronic

leveling to adjust

Checking Tribrachs

Tribrachs

•Use GDF22•Check with a Ring

Easy to adjust … extremely durable.

Tribrach Checker

Seco Tribrach Adjusting Cylinder 2001-00

Catalog# 106360

APE Price: $47.95

Donna George 800-241-6223

Accuracy & PrecisionTribrachs

Tribrach Bubble Adjustment

� Level up the instrument with the electronic level, assuming that the electronic level is correctly adjusted.

� Remove the instrument from the tribrach.

� The bubble of the tribrach must be centered.

� If it extends beyond the circle, use the adjusting pin in conjunction with the two cross headed adjustment screws to center it.

� After adjustment, no screw shall be loose.

Laser Plummet

� Built into the alidade� Does not require user

adjustment� Adjustable intensity of beam� Makes for fast, easy setup

Laser Plummet

� Eliminates tribrach errors� Good for marks in dark

monument boxes� Fine laser beam for precise

pointing� Requires inexpensive tribrach

without optical plummet

InstrumentsCare & Transport

TPS1200

Automatic Target Recognition (ATR)Receiver

Distance Measuring System (EDM)ReceiverEmitter IREmitter RL

PowerSearchEmitterReceiver

Angle Measuring System (Hz)Glass circleEmitterReceiver

Electronic Guide Light (EGL)

Emitter

Angle Measuring System (V)

EmitterGlass circle

Tilt SensorEmitter

Oil surface

Motorization

Laser PlummetEmitter

Instrument CareDamp Instrument & Case

� Dry instrument & Case� Leave case open� Storing a wet instrument can

cause fungus to grow on optics which will etch or destroy coatings

� Remove debris, and dirt� Dry leaves and grass turn into

fine powder� Can cause more damage than

moisture

Instrument CareEyepiece & Objective

� Never use fingers, paper products or solvents to clean or dry optics

� Use lint free Q-tips and pure alcohol

� Change Q-tip after each wipe as not to contaminate alcohol

� Camera lens cleaning tissue is okay, but tends to smear rather than clean

Instrument CareClimatize Prior to Use

� Allow 1 minute for:� Every 1°C or 2°F change in

temperature� Example

70°F inside truck30°F outside

(70-30) * 0.5 = 20 minutes

Could make a difference!� There can be 0.5 arc second

of error per 1°F of temperature difference

Instrument CarePreventative Maintenance (PM)

� Annual – Normal use such as land surveys and topo

� Semi-Annual – Occasional construction layout in dusty conditions and occasional transportation over rough terrain

� Quarterly – Continuous use on construction sites with dust wet conditions, constant vibration from heavy equipment passing by, and regular transportation over rough terrain

Accuracy & PrecisionCalibrationInstrument Errors

� Compensator longitudinal and transversal index errors (l,t)

� Vertical index error, related to the standing axis (i)

� Hz collimation error, also called line of sight error (c)

� Tilting axis error (a)

� ATR zero point error for Hz and V (ATR)

� Instrument errors occur if the standing axis, the tilting axis and the line of sight are not precisely perpendicular to each other.

Accuracy & PrecisionCalibration, continuedInstrument Errors, continued

� During the manufacturing process, the instrument errors are determined and set to zero. These errors can change and it is recommended to redetermine them in the following situations:

� Before the first use

� Before EVERY high precision survey

� After rough or long transportations (even if it is being returned/shipped from a service center)

� After long working periods

� After long storage periods

� If the temperature difference between current environment and the temperature at the last calibration is more than 20°C or 68°F.

Instrument CareThis one may need some callibration & cleaning!

OppsBuzzkill

Guess What?

You’re the Leica Salesman’sBEST FRIEND

PrismsCare� Avoid scratching� Keep CLEAN!

� A dirty prism can reduce return signal, thus reduce EDM performance

� Cleaning method same as for objective lens and eyepiece

BatteriesGeneral Specification

-4 to +131-4 to +131-4 to +131Operating Temperature (°F)

NoYesYesMemory Effect

> 500< 800< 1000Charge Cycles

3.61.21.2Nominal Voltage

Li-IonNiMHNiCd

BatteriesSelf Discharge

358

3288

104Li-Ion

103090

3288

104NiMH

71530

3288

104NiCd

% Loss per MonthStorage Temp. (°F)Cell Type

� Self discharge dependent on temperature and humidity� High temperatures and humidity accelerate self-discharge

How does the technology really work?

EDM EDM -- TypesTypes

Two Technologies

� Phase-Shift

� Timed-Pulse (Time of Flight)

30 40 50

PhasePhase--shift EDMshift EDM

PhasePhase--shift EDMshift EDM

Wavelength

ω

Phase Shiftp

Distance = nω + p

2

Timed Pulse EDMTimed Pulse EDM

tcD ∆=21

Reflectorless EDM Measuring BeamReflectorless EDM Measuring BeamA small spot is important

� Accuracy

� Pointing confidence

A visible spot is important

� Pointing confidence

� Field calibration

� Work in dark areas

Beam size at 30 USft

Pulsed EDM:60mm x 40mm

0.20 x 0.13 USft

Leica RL-Phase:20mm x 12mm0.07 x 0.04 USft

Angle Reading SystemsAngle Reading Systems

Encoders

Angle Reading System Angle Reading System -- IncrementalIncremental

An incremental system only measures the angular relationship between an arbitrary point and the position to which it has beenrotated.

The arbitrary point may be the circle position at the instant the theodolite encoder is powered on.

Angle Reading System Angle Reading System –– Absolute EncoderAbsolute Encoder

Absolute refers to the fact that every graduation possesses a definite angular value.

An absolute encoder does not require a zero setting or any special initialization.

How does the technology really work?

� How can we improve aiming accuracy?

Use Automatic Target Recognition

How does ATR work?How does ATR work?

What was the first surveying instrument?

Leica Geosystems has developed a unique passive prism technology for quick and accurate pointing. It is called ATR, Automatic Target Recognition.

No power required at the prism.

Automatic Target Recognition Automatic Target Recognition -- ATRATR

How ATR Works (Cont)How ATR Works (Cont)

CCD Source Diode

CCD Array

How ATR How ATR Works_HDWorks_HD CameraCamera

How ATR Works (Cont)How ATR Works (Cont)

How ATR WorksHow ATR Works

How does the technology really work?

� Prism Constants

Prism Constant Prism Constant –– Calculation for Corner CubeCalculation for Corner Cubea + b + c = Distance light travels in the glass cube (the path of the light through the prism is always the same length).

t = Distance from face of prism to the corner of the cube.

d = Distance from the face of the prism to the vertical axis (plumb line) of the prism holder.

1.517(t) = The equivalent air distance light travels because of refractive index of glass.

R = The “virtual” corner of the cube

O = Prism constant

Prism constant calculation:

O = d – (1.517 x t)

t

1.517(t)

R

Od

Vertical Axis of Prism Holder

From EDMa

c To EDMb

Prism Constant ExamplePrism Constant Example

Vertical Axis of Prism Holder

- 30mm

- 34.4mm

+ 4.4

Additive ConstantAdditive Constant

The additive constant is a system constant that depends on the instrument and reflector being used.

It is only valid for the combination of both.

Manufacturers set the additive constant to zero for their combination.

Typically this is done through the software as Leica does.

Others displace the center of the prism from the vertical axis of the holder which can cause errors if the prism is not correctly aligned to the line of sight of the EDM.

The additive constant can be determined with a known true distance or with unknown true distances.

Checking Prism ConstantsChecking Prism Constants

A B

How does the technology really work?

� How do I know where the distance is measured to?

Coaxial Coaxial

What other factors need to be considered?

� Temperature

� Pressure

� Refraction

� Elevation

� Centering

� Height measurement

� EDM Specs

PPM Correction PPM Correction –– Leave it at Zero?Leave it at Zero?

Comparison of leaving the instrument set to 0 ppm under the following conditions:

Temperature = 80°F, Elev. = 1000 ft.

PPM Correction = 25

A 25ppm error is .025 per 1000 ft.

Or .065 in 2640 ft.

If the ppm setting is 0 and the elevation is 1000 ft. the temperature would have to be approx. 35°F.

Accuracy & PrecisionPPMProportional Errors are measured in Parts Per Million

(PPM)

1 unit of error per 1,000,000 unit equals 1 PPM

.001’ error per 1,000’ = 1 PPM

Rule of Thumb:

� 1 PPM for every 2° F changeeg 40° am and 70° pm = 30° change = 15 PPM

� 1 PPM for every 90’ elevation change

Accuracy & PrecisionPPMProportional Errors

Accuracy –Then of a 1000’ EDM Measurement

± .007’ Constant Error

± .002’ Proportional Error

± .015’ Temp Error

± .005’ Pressure Error

± .010’ Centering Error

± .010’ HI Error

± .006’ Refraction Error

± .002’ Elevation Error

Total - ± .062’ Uncertainty

Effects of Angle AccuracyEffects of Angle Accuracy

Relationship Between angle accuracy & relative accuracy

1 in 412,5000.000 0020.5”

1 in 206,2000.000 0051”

1 in 103,1000.000 0092”

1 in 68,7000.000 0143”

1 in 41 2000.000 0245”

1 in 20,6000.000 04810”

1 in 10,3000.000 09620”

Relative Accuracy

Linear Error at 100 Ft

Angle Measurement

Accuracy

EDM accuracy by rangeAccuracy 100 ft. 1000 ft. 2640 ft. 5280 ft.

±(2mm+2ppm) ± 0.007ft ± 0.009ft ± 0.012ft ± 0.017ft.

±(2mm+3ppm) ± 0.007ft ± 0.010ft ± 0.014ft ± 0.022ft.

±(2mm+5ppm) ± 0.007ft ± 0.012ft ± 0.020ft ± 0.033ft.

±(3mm+2ppm) ± 0.010ft ± 0.012ft ± 0.015ft ± 0.020ft.

±(3mm+3ppm) ± 0.010ft ± 0.013ft ± 0.018ft ± 0.026ft.

±(3mm+5ppm) ± 0.010ft ± 0.015ft ± 0.023ft ± 0.036ft.

±(5mm+2ppm) ± 0.017ft ± 0.018ft ± 0.022ft ± 0.027ft.

±(5mm+3ppm) ± 0.017ft ± 0.019ft ± 0.024ft ± 0.032ft.

±(5mm+5ppm) ± 0.017ft ± 0.021ft ± 0.030ft ± 0.043ft.

Distance Measured

(Feet)

Distance Measured

(Feet)

Distance Accuracy

(Feet)*

Distance Accuracy

(Feet)*

Required AngleAccuracy(Seconds)

Required AngleAccuracy(Seconds)

Required InstrumentRequired

Instrument

100’200’300’500’

1000’2000’5280’9000’

13100’22900’45900’

.0169’

.0174’

.0179’

.0189’

.0214’

.0264’

.0428’

.0614’

.0819’

.1309’

.0623’

*Standard &PPM Corrections

35”18”12”

8”4”3”

1.6”1.4”1.3”1.2”0.3”

Transit

T-16 / TPS-400 SeriesT-1 / TPS-700 Series

TPS-800 Series

T-2 / TPS-1200 Series

T-3 / T2000 Series

Accuracy & PrecisionDistance - Angle Accuracy Requirement

Traverse Closure Combining Angle & Distance Uncertainty Traverse Closure Combining Angle & Distance Uncertainty @ 1000m@ 1000m

3” Inst. With an EDM ± (5mm+3ppm)

214,400183,400152,300120,60096,0000.5”160,000144,900128,000107,40089,4001”95,30091,70086,90079,50071,3002”66,40064,80063,00060,10056,3003”40,70040,20039,70039,00037,9005”20,50020,50020,40020,30020,20010”

10,30010,30010,20010,20010,20020”±(2mm+2ppm)±(3mm+2ppm)±(3mm+3ppm)±(5mm+3ppm)±(5mm+5ppm)Angle\EDM

Sources of Errors in GPS

Multipath effect

The multipath effect is caused by reflection of satellite signals (radio waves) on objects. It was the same effect that caused ghost images on television when antennae on the roof were still more common instead of today's satellite dishes.

For GPS signals this effect mainly appears in the neighborhood of large buildings or other elevations. The reflected signal takes more time to reach the receiver than the direct signal. The resulting error typically lies in the range of a few meters.

"Satellite geometry“ DOP

Another factor influencing the accuracy of the position determination is the "satellite geometry". Simplified, satellite geometry describes the position of the satellites to each other from the view of the receiver.

Good geometrical alignment of two satellites

Bad geometrical alignment of two satellites

GDOP (Geometric Dilution Of Precision); Overall-accuracy; 3D-coordinates and time

PDOP (Positional Dilution Of Precision) ; Position accuracy; 3D-coordinates

HDOP (Horizontal Dilution Of Precision); horizontal accuracy; 2D-coordinates

VDOP (Vertical Dilution Of Precision); vertical accuracy; height

TDOP (Time Dilution Of Precision); time accuracy; time

Satellite Orbits

Although the satellites are positioned in very precise orbits, slight shifts of the orbits are possible due to gravitation forces. Sun and moon have a weak influence on the orbits.

The orbit data are controlled and corrected regularly and are sent to the receivers in the package of ephemeris data. Therefore the influence on the correctness of the position

determination is rather low, the resulting error being not more than 2 m.

Atmospheric effects

Another source of inaccuracy is the reduced speed of propagation in the troposphere and ionosphere. While radio signals travel with the velocity of light in the outer space, their propagation in the ionosphere and troposphere is slower.

This is the main factor limiting Baseline lengths

Influenced propagation of radio waves through the earth's atmosphere

Autonomous Positioning Errors

Ionospheric effects ± 5 meter

Shifts in the satellite orbits ± 2.5 meter

Clock errors of the satellites' clocks ± 2 meter

Multipath effect ± 1 meter

Tropospheric effects± 0.5 meter

Calculation- und rounding errors ± 1 meter

Altogether this sums up to an error of ± 15 meters. Corrections by systems like WAAS and EGNOS, which mainly reduce ionospheric effects, but also improve orbits and

clock errors, the overall error is reduced to approximately ± 3 - 5 meters.

Dual Frequency Receivers receiving correction from a Base reduce these errors to

1 cm Horz and 2 cm Vert

Any Questions?

Answer!