Different authors use sub-ionospheric latitude and longitude to to express latitudinal gradient of TEC, Das et al., 2014. How can we find the GPS tracks in terms of sub ionospheric latitude and longitude ?
Dear Teshome Dugassa,
I suggest you to see links and attached files in topics.
-Ionospheric Space Weather: Longitude Dependence and Lower Atmosphere ...
https://books.google.dz/books?isbn=1118929209
-GPS Study Guide Flashcards | Quizlet
https://quizlet.com/39204576/gps-study-guide-flash-cards/
Best regards
h =Assumed Ionospheric height
R = Radius of the earth
Elev_use = Satellite Elevation
azi_use = Satellite Azimuth
sta_lat = GNSS receiver latitude
sta_lon = GNSS receiver longitude
a = R*COS(Elev_use*!Pi/180.0)/(R+h)
Oblique = SQRT(1.0-a^2.0)
p = !PI/2 - Elev_use*!PI/180.0 - ASIN(a)
lat = asin(sin(stalat*!PI/180.0)*cos(p) + cos(stalat*!PI/180.0)*sin(p)*cos(azi_use*!PI/180.0))
lon = stalon*!PI/180.0 + asin(sin(p)*sin(azi_use*!PI/180.0)/cos(lat*!PI/180.0))
lat is the latitude of ionospheric pierce point (IPP) in radians.
lon is the longitude of ionospheric pierce point in radians.
Oblique is the angle the ray path makes with the assumed ionospheric thin shell.
p is the angle subtended at earth center.
!PI/180 factors are used for degrees to radian conversion, since these lines of code come from my IDL scripts (which operate in radians). Remove these factors in all locations or convert to degrees if your coding language uses degrees.
Be careful, some authors will reference an equation for longitude that incorrectly uses the station latitude instead of the IPP latitude. This is due to a typo in one of the older texts in the field.
David R. Themens Could you confirm as to whether the Asin(a) factor in the equation for p stands for arcsin(a)? Also, the asin() factors in the equations for lat and lon (IPP latitude and longitude) too stands for arcsin() right? Its NOT a (= R*COS(Elev_use*!Pi/180.0)/(R+h)) multiplied with sin().
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