Crop survey, dated 1400-1390 B.C. The Greek historian Herodotus, who lived in the fifth century B.C., relates that around 1400 B.C., the pharaoh Sesostris "distributed the land to all the Egyptians, giving an equal square portion to each man, and from this he made his revenue and if the river should take away any man's portion the king used to send men to examine and to find out by measurement how much less the piece of land had become, in order that for the future the man might pay less" Thus, it appears that the first known reference to the science of surveying shows how it was used to measure property boundaries in order to ensure the collection of taxes or rent at the proper rate.

In this photograph, surveyors use an invar tape to measure a base line through a house in Pasadena, California. Invar, an alloy of nickel and steel having a very low coefficient of expansion, resolved the thermal expansion problem associated with the use of other metal rods and tapes for distance measurement.

Taping in southeast Alaska, 1916

ntrebri studeni1. ?2. ?3. ?4. ?5. ?This black and white illustration, included to give an idea of some of the challenges of the equipment of the era, shows Survey of the Coast Superintendent Ferdinand Hassler directing the placement of his specially designed "Great Theodolite" while surveying on Fire Island, New York. The theodolite was used for precise and accurate angle measurements. He also designed and built an apparatus consisting of four two-meter bars that could be laid end-to-end to determine distance.

This illustration, drawn in 1854, shows a Coast Survey party measuring a base line in Key Largo, Florida.The party is using an apparatus called the Bache-Wurdemann device.This device, which was essentially two bars encased in aluminum, was designed to help reduce errors caused by the expansion and contraction of metal rods during measurements.

This photograph shows a surveyor using a tape stretcher. In the early 1900s, tapes eventually replaced the bar apparatus as the practical means for measuring distances.

In this photograph, an iced-bar apparatus is being aligned with a striding level. This apparatus, designed in ongoing efforts to combat the problem of thermal expansion of metal rods used to measure distances, is essentially a bar covered with ice.

Principiul generalMsurarea electronic de distaneund (luminoasa sau radio)

Istoria E.D.M.Electronic Distance Measurement1938, fizicianul suedez Erik Bergstrand studiaz posibilitatea msurrii vitezii luminii cu ajutorul unui sistem optic original,Sistemul controla frecvena undelor luminoase cu ajutorul unui cristal oscilator,Dup nou ani de cercetri ajunge la concluzia c viteza luminii este de 299,79310,2 km/sec.1948, Bergstrand sugereaz (i indic modalitatea) companiei suedeze AGA, s produc un aparat de msurat electronic distanele, care va fi denumit Geodimeter,

ACESTA ESTE NCEPUTUL EPOCII DE MSURARE ELECTRONIC A DISTANELOR

Primul aparat de tip EDM/Geodimeter cntrea cteva zeci de kg. i putea msura distane pn la 35 km!Este trecut i testul preciziei: se constat experimental c aparatul msoar distane cu o precizie superioar celei mai precise modaliti de msurare direct-firul de invar.1955, este lansat Geodimeter model 2, care putea msura distane pn la 50 km.Aparatul continu s se perfecioneze, crescnd precizia.

TellurometrulDup cercetri efectuate tot din anii40, n 1957 n Africa de Sud se lanseaz primul aparat.Aparatul folosete n procesul de msurare microunde.Microundele sunt mai afectate de factorii atmosferici ca i undele luminoase metoda este mai puin precis.Cu toate acestea aparatul poate msura distane pn la 50 km.

Tellurometrul, cca 1959

Cea de a doua generaie GEODIMETERGeodimeter evolueaz rapid dup 1960, astfel:Greutatea scade de peste 10 ori,Timpul de msurare scade de la 45' la 10 ,Lampa cu tugstren este nlocuit cu o lamp cu vapori de mercur, n varianta 4.Primul aparat laser este inventat de George Leslay de la Coast and Geodetic Survey, SUA, care nlocuiete lamp cu vapori de mercur, cu un laser neon gaz, n 1966.

n 1964 lmpile cu vapori sunt nlocuite cu tranzistori, Geodimeter model 6,Se reduce foarte mult timpul de msurare,WILD DI 10 DISTOMAT este unul dintre primele aparate de acest gen, care utilizeaz semiconductori, foto-diode pentru undele luminoase.n anul 1969 aparatul ptrunde n SUA, dar n paralel HP, lanseaz modelul HP Model 3800B, care utiliza o diod emitoare de unde luminoase de cu ajutorul unui sistem de galliu-arseninid,Amndou aparatele prezentau comparativ cu metodele anterioare faciliti de utilizare,Apar n acelai timp aparate pentru topografie i cadastru care msoar distane scurte de pn la 10 km.

HP Model 3800B EDM

AGA MODEL 1976

Epoca Staiilor topografice totaleStaie topografic total= teodolit electronic+EDM1983

ZEISS1968 Zeiss combin cele dou instrumenteNumete noul aparat ELTA- tahimetru electronicPrecizia de msurare a unghiurilor 3',Pentru distane prin unde n infrarou se pot msura distane pn la cca.2 km.Aparatul necesit prisme reflectoare(primele aparate foloseau oglinzi plate, apoi sferice)

Prisme reflectorizante

A key component of an electronic distance measurement instrument is the reflector system, which bounces light signals of a known wavelength to a reflector to determine distance. The prism system shown in this photograph was one of the systems used in Geodimeters.

AGA Geodimeter Model 6

Distance measurement Physical unit = metre (m) = the length of the path travelled by light in vacuum during a specific fraction of a second (1/299 792 458 s).

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kilo-km103hecto-hm102milli-mm10-3deci-dm10-1micro-m10-6centi-cm10-2nano-nm10-9

Distance measurement methodsmeasurement with a tapeoptical methods a) measurement of a parallactic angle b) stadia range finderelectro-optical methods a) phase distance meter b) distance meter measuring transit time

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1. Distance measurement with a tape tape length 20 50 m, the smallest division 1 mmmaterial steel, invar (Ni, Fe), plasticmeasured distance is split into sections which are shorter than the tape length, these sections should be in a straight line horizontal distance is measured (it is assured by a plummet)measurement is always performed twice back and forth in a flat terrain or down from the top twice *

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Errors of measurement with a tapeif the real tape length is not known: the tape should be calibrated,if the temperature during a measurement is not the same as the temperature during the calibration: the temparature correction should be introduced ot = (t t0). . d, d measured distance, thermal line expansion coefficient, t temperature during the measurement, t0 temperature during the calibration,*

if the sections are not in a straight line,if the tape is stretched less than 50 N or more than 100 N,if the tape is not horizontal,if the tape is sagged: it depends on the tape length if a wrong value is read on the tape

Accuracy of the distance measurement with a tape is about 3 cm for 100 m (1: 3000 of a measured distance). *

2a) Measurement of a parallactic angle *

horizontal stadia rod of known length l is placed perpendicular to the measured distance Dhorizontal angle is measured by a theodolite horizontal distance is calculated

accuracy 1 mm for 100 m (1:100 000)*

2b) Stadia range finder horizontal line of sight*

there are 2 short lines = stadia lines in the field of view of all theodolites and levelling instruments angle is invariable (it is given by the distance between stadia lines and by the focal distance f), a rod interval l is measured (it is read on a levelling rod)

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measured distance D is horizontalusually k = 100

if the line of sight is not horizontal, a rod interval l and a zenith angle z are measured and then

accuracy 0,1 m for 60 m (1:600)*

Stadia range finder slope line of sight *

3. Electro-optical distance measurementthere is a transmitter of electromagnetic radiation on a point and a reflector on another onereflector: 1. trigonal reflector 2. arbitrary diffuse surfaceprinciples of distance measurement: 1. evaluation of a phase or frequence of modulated electromagnetic radiation, 2. signal emission and transit time measurement.*

slope distance is measured with an electronic distance meter = length of a join between the instrument and the prism (target) additive constant of the instrument and the target set = systematic difference between measured and true distance given by the positions of instruments and targets reference points. The additive constant is given by the producer of the instrument and it should be introduced to a measurement.electronic distance meter can be embeded in so called total station (electronic theodolite + electronic distance meter)*

Accuracy of electronic distance meters = X + Y ppm X invariable part of the standard deviation, Y variable part of the standard deviation (it depends on the value of a measured distance)

E.g. = 3 mm + 2 ppm the standard deviation of measured distance is 7 mm for the distance 2 km (= 3 + 2*2) *

3a) Phase distance meter*

distance meter signals a modulated wave with the phase 0 and a wave with the phase 1 is turned back. The distance is characterized by the phase difference .the wave has to be longer than measured distance (it is not possible to determine a number of the whole waves) more than one wavelength are usually used for measurement, e.g. wavelengths 1000 m, 10 m, 1 m and then the values 382 m, 2,43 m, 0,428 m give the result 382,428 m.*

3b) Distance meter measuring transit time signal is emitted by the distance meter and transit time t is measured

high accuracy of the transit time measurement is needed therefore these distance meters are less often used*

Corrections of measured distancesphysical correction of a distance for measurements with electronic distance metersmathematical reduction of a distance for coordinate calculations*

Physical correction wavelength depends on atmosphere which the signal comes through, it depends on atmospheric temperature and pressure mainly value of physical correction is set in a distance meter (it is calculated using formulas given by the producer of the distance meter)it is possible to enter the temperature and the pressure to the most of modern distance meters and the correction is calculated automatically *

Mathematical reduction Measured distance d which is shorter than 6 km has to be: 1. reduced to a curvature on the reference sphere (to so called sea level horizon), 2. reduced to the plane of the cartographic projection (e.g. S-JTSK) *

1. Mathematical reduction to the sea level horizon*

r reference sphere radius (6380 km)h sea level height (elevation)*

2. Distance projection reduction (S-JTSK)

for short distances

The scale error value m is calculated or found out using the scale error isolines map.

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