How to implement the st_angle function

[LemonLiTree]

I want to achieve the same function as the st_angle function in bigquery:
https://cloud.google.com/bigquery/docs/reference/standard-sql/geography_functions#st_angle
I tried a lot of ways but didn't get the correct result：

`

    const S2Point* point1 = (const S2Point*)p1;
    const S2Point* point2 = (const S2Point*)p2;
    const S2Point* point3 = (const S2Point*)p3;
    S2Point normal1 = point2->operator-((S2Point&)point1);
    S2Point normal2 = point2->operator-((S2Point&)point3);
    *angle = normal1.Angle(normal2);
    if ( normal1.CrossProd(normal2).z() < 0){
        *angle = 2 * M_PI - *angle;
    }

`

I want to ask how can I change it Or how can I achieve this function

[smcallis]

It looks like we convert the 3 points to lat/lon, then compute the bearing using this <https://web.archive.org/web/20200416084231/http://mathforum.org/library/drmath/view/55417.html> algorithm. The angle is then the difference in the bearing between point2->point3 and point2->point1

…

On Wed, Mar 29, 2023 at 3:35 AM Liqf ***@***.***> wrote: I want to achieve the same function as the st function in bigquery: https://cloud.google.com/bigquery/docs/reference/standard-sql/geography_functions#st_angle I tried a lot of ways but didn't get the correct result： const GeoPoint* point1 = (const GeoPoint*)p1; const GeoPoint* point2 = (const GeoPoint*)p2; const GeoPoint* point3 = (const GeoPoint*)p3; S2Point normal1 = point2->CrossProd((S2Point&)point1); S2Point normal2 = point2->CrossProd((S2Point&)point3); *angle = normal1.Angle(normal2); I want to ask how can I change it — Reply to this email directly, view it on GitHub <#308>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAGEMKT7ACCPGA5BPWHOSNDW6P65BANCNFSM6AAAAAAWLWRRMQ> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[LemonLiTree]

point2->point1 is point2->operator-((S2Point&)point1); right?

[smcallis]

Sorry I wasn't clear, say you have a function Bearing written with that algorithm, then ST_Angle(point1, point2, point3) = Bearing(point2, point3) - Bearing(point2, point1).

…

On Thu, Mar 30, 2023 at 12:22 AM Liqf ***@***.***> wrote: point2->point1 is point2->operator-((S2Point&)point1); right? — Reply to this email directly, view it on GitHub <#308 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAGEMKTN3O7RPA5PRUOAUULW6URCNANCNFSM6AAAAAAWLWRRMQ> . You are receiving this because you commented.Message ID: ***@***.***>

[LemonLiTree]

cool i got it,thank you very much