Computation of SDA and SDB for Distance Observations
1.0 Electro-magnetic Instruments
Instrument Instrument code SDA (cm) SDB (ppm)
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MA101 TELLUROMETER 52T0x 3.0 x sqrt(3/N) 3.0 x sqrt(3/N)
x = N = number of double measurements
MRA101 52T01 5.2 5.2
MICROFIX 52MFX 1.5 3.0
16 measurements on each end of a double line
CA1000 Tellurometer Inc. 52CA1 3.0 10.0
For the mean of 2 measurements made in opposite directions where
1 measurement is the mean of observations on 7 frequencies
Aerodist 52AD2, AD3, AD4 120.0 7.0
See special centering 52AD1 170.0 10.0
errors for this type 52AE, AO
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The mean of observations made on 13 cavities comprises 1 single measurement.
The mean of 2 single measurements made in opposite directions by exchanging master
and remote roles comprises 1 double measurement.
MRA-5 TELLUROMETER 52T5x 1.0 x sqrt(3/N) 5.0 x sqrt(3/N)
(10 cavities)
MRA-4 TELLUROMETER 52T4x 1.5 x sqrt(3/N) 3.0 x sqrt(3/N)
MRA-3 TELLUROMETER 52T3x 3.0 x sqrt(3/N) 3.0 x sqrt(3/N)
MRA-2 TELLUROMETER 52T2x 5.0 x sqrt(3/N) 3.0 x sqrt(3/N)
MRA-1* TELLUROMETER 52T1x 5.0 x sqrt(4/N*) 3.0 x sqrt(4/N*)
x = N = number of double measurements except for the MRA-1 where x and N are
the number of single measurements.
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* Note: Master and remote measuring modes are not interchangeable on the MRA-1.
N therefore represents the number of single measurements.
2.0 Electro-optical instruments
Instrument Instrument code SDA (cm) SDB (ppm)
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Geodimeter (AGA) 52Gxy 1.0 x sqrt(6/N) 1.2 x sqrt(6/N)
x = instrument's model number
y = N = number of measurements on each of 3 frequencies
Distomat
Kern DM500 52DI 1.0 x sqrt(6/N) 1.2 x sqrt(6/N)
Wild DI4, DI41, DI5
DM502 52DI 0.5 5.0
DM503 52DI 0.3 2.0
AGA 14A, 76, 78 52Gxy 1.0 x sqrt(10/N) 2.0 x sqrt(10/N)
N = number of measured sets
MA100 52MA1 0.2 2.0
MEKOMETER 52MEK 0.1 0.3
HP 3800, 3800A, 3805, 3820A 52HPx 0.3 x sqrt(10/N) 10.0 x sqrt(10/N)
3820A (x = N : measurements)
RANGER 3,4 and 5 52RxA 1.0 2.4
20 measurements, x is the instrument model: 3, 4 or 5
RANGEMASTER 52RMx 1.0 1.2
20 measurements, x = A for the RANGEMASTER and x = 2 for the RANGEMASTER 2
Citation 1410, 1450 52CI 0.5* 5.0*
Nikon 52NI 0.5* 5.0*
Pentax 52PE 0.5* 5.0*
Sokisha RED 2 52SK 0.5* 5.0*
Tachymat TC1, TC1L 52TC 0.5* 5.0*
Topcon DM-S1, DM-S2 52TP 0.5* 5.0*
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* Manufacturers values
3.0 Non electronic methods
Instrument Instrument code SDA (cm) SDB (ppm)
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Steel tape:
Baseline:
Weights and straining 52BLW 0.0 1.0
bars used
Spring balances used 52BLS 0.0 3.0
Short lengths:
Less than one tape 52 TL 0.4 0.0
length 52TL
More than one tape 52 TL 1.0 0.0
length 52TL
Subtense bar: 52 SB 100 x L x L x sec / B 0.0
L = linelength in meters
B = lenght of sbutense bar in meters
sec = sine of 1 second
Auto-reduced distance 52AUT 10* 20*
Stadia 52STA * *
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* Consultation is advised in deciding for particular cases on SDA and SDB
values for these data types
Revised 6 Dec 98 by Mike Craymer