2.2　Symbols

A——nominal fixed error of GPS receiver；

a——nominal fixed error of electromagnetic distance measurement instrument；

B——nominal scale error coefficient of GPS receiver；

b——nominal scale error coefficient of electromagnetic distance measurement instrument；

C——collimation error；

D——leg length measured with electromagnetic distance measurement instrument；

Dg——length of leg on Gauss projection plane，m；

DH——length of survey leg reduced to the average datum plane of survey area，m；

Dp——horizontal distance of survey line；

D0——length of survey leg reduced to the reference ellipsoid，m；

d——distance between adjacent points in GPS network，average leg length of control network，or discrepancy between elevation differences obtained from reciprocal observation；

f——principal distance of aerial camera，mm；

fc——deflection；

fh——closing error of connecting or loop route；

fβ——angular misclosure in closed-loop traverse，or azimuth misclosure in connecting traverse；

H——water depth，or height of building or structure；

Hd——basic contour interval in topographic maps；

Hm——average elevation of both ends of survey leg；

Hp——average elevation of survey area；

h——elevation difference；

hm——height of geoid above the reference ellipsoid in survey area；

i——included angle between collimation axis and leveling tube axis，index error，serial number of triangle，least count of circle，or predominant inclination；

K——atmospheric refraction coefficient，magnification ratio of mapping scale to photograph scale，or ratio of lengths measured by two different coordinate systems；

L——route length，length of survey segment，face left reading of vertical angle，or length of collimation line；

M——denominator of mapping scale，or denominator of photograph scale；

Mh——elevation RMSE of densification point；

Mp——point RMSE；

Ms——horizontal RMSE of densification point，or RMSE of horizontal displacement；

Mw——total RMSE of elevation difference；

MΔ——accidental RMSE of elevation difference；

Mcontrol——RMSE of control point，m；

Mcommon——RMSE of common point，m；

m——RMSE；

mD——distance RMSE；

mg——angle RMSE of fixed angle；

mα1 and mα2——RMSE of the starting azimuth；

mβ——angle RMSE；

and——relative length RMSE of the starting leg；

——average relative length RMSE of various legs；

N——number of non-simultaneous observation loops，connecting routes，traverses or closed loops；

n——number of survey stations，survey segments，legs，observation points，triangles，or photograph baselines；

P——weight of measurement；

R——mean radius of the Earth curvature，face right observation；

RA——curvature radius of the normal section of reference ellipsoid along the measured leg direction；

Rm——average curvature radius of reference ellipsoid at the midpoint of leg；

r——correction for the earth curvature and refraction；

S——leg length or slope distance；

W——misclosure；

Wj，Wb，Wf，Wg，and Wz——limits of angle-pole condition parameter，leg（baseline）condition parameter，azimuth condition parameter，fixed angle condition parameter，and leg-pole condition parameter respectively；

Wr——limit for the difference between observed and calculated angles；

Wx，Wy，and Wz——misclosure in various coordinate components of simultaneous and nonsimultaneous observation loops；

ym——average of horizontal coordinates at both ends of leg；

α——vertical angle，ground inclination，or length ratio coefficient；

β——angle for calculating distance；

αw——sum of the cotangents of both base angles of the peripheral leg opposite to polar point；

af——sum of cotangents of the adjacent base angles at both ends of radial leg which connects with the polar point of a polygon，sum of cotangents of the adjacent base angles at both sides of the inner radial leg of quadrangle，or difference between cotangents of the adjacent base angles of two external radial legs of quadrangle；

δ1-2——corrected value of angle observed from Survey Station 1 to Collimated Point 2；

δ2-1——corrected value of angle observed from Survey Station 2 to Collimated Point 1；

Δ——discrepancy or misclosure；

Δd——length discrepancy；

Δα——compensating error of self-leveling level；

μ——RMSE of unit weight；and

σ——length RMSE of baseline.