Question

Hello again,

SaasTropModel class has a bug. There is a wrong implementation of the formula that computes the wet zenith delay (see line 1527, TropoModel.cpp). According to the reference given in the class definition, i.e., Saastamoinen (1972) the formula inside the parentheses should be:

(1255/T + 0.5) * humid

while gpstk implementation is

double delay = 0.0022768 * humid * 1255/(temp+273.20) / (1 - 0.00266 * ::cos(2*latitude*DEG_TO_RAD) - 0.00028 * height/1000.);

Thus, in my opinion the right implementation would be:

double delay = 0.0022768 * humid * (1255/(temp+CELSIUS_TO_KELVIN)+0.5) / (1 - 0.00266 * ::cos(2*latitude*DEG_TO_RAD) - 0.00028 * height/1000.);

References:

  • Saastamoinen, J., 1972, “Atmospheric Correction for the Troposphere and Stratosphere in Radio Ranging of Satellites,” Geophysical Monograph 15, Henriksen (ed), pp. 247–251.
  • Saastamoinen, J., 1973, “Contributions to the theory of atmospheric refraction,” In three parts, Bull. G`eod., 105, pp. 279–298, 106, pp. 383–397, 107, pp. 13–34.

Best regards, Octavian

-- OctavianAndrei - 23 Jun 2008

Answer

ALERT! If you answer a question - or have a question you asked answered by someone - please remember to edit the page and set the status to answered. The status is in a drop-down list below the edit box.

You are right. Fixed at 1262. Thanks Octavian.

-- BrianTolman - 24 Jun 2008 No such template def TMPL:DEF{PROMPT:supportquery}

Topic revision: r2 - 24 Jun 2008, BrianTolman
 

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