Correction to the zenith angle for R?

[zvezdochiot]

Hi @zsiki .

Subj.

https://github.com/zsiki/GeoEasy/blob/b1bd171039274157195c0742b4db28445ad28173/src/calcgeo.tcl#L268-L269 Aligning the zenith to the median plumb line:

if {[expr {abs($R)}] > 1e-4} {
    set dZR [expr { $d / $R / 2 }] # R = 6370009.0 m, dZR in radians.
}

See also https://github.com/Geo-Linux-Calculations/geofindkey/commit/0fa0357bd718dea087704ceb291c141eb80662f2

PS: The dZR correction is:

• for d = 250 m - 4";
• for d = 500 m - 8";
• for d = 1000 m - 16";

[zsiki]

It is considered as the effect of refraction and Earth curvature. You can turn it on/off in the Calculation parameters dialog "Calculate refraction and Erth curvature" (refr variable). It is used only for distance longer than 400 meters for trigonometric height calculation.

[zvezdochiot]

Hi @zsiki .

https://github.com/zsiki/GeoEasy/blob/b1bd171039274157195c0742b4db28445ad28173/src/geo_easy.tcl#L104 Not used. I have searched and cannot find where this is used. Tell me?

[zsiki]

loadgeo.tcl line 186.

[zvezdochiot]

Hi @zsiki .

https://github.com/zsiki/GeoEasy/blob/b1bd171039274157195c0742b4db28445ad28173/src/loadgeo.tcl#L184-L206

I could not figure it out completely, but I trust you.

(IMHO):

185. scale correction for elevation above sea level.
186. something incomprehensible to me .