2 planar angles from the origin

[masterjebbi]

I have X Y Z coordinate data in a time series as three columns and 1000 rows. This 3D point is moving, in that every row has a new X Y Z position. The 3D point is not moving very fast or far. I am using this data to emulate (model) a device that sits at the GCS origin 0,0,0. This device measures direction toward a 3D point as two orthogonal plane angles. In this case one part of the device measures the XZ angle, and the other part measures the YZ angle. How do I report my data as if it is being read by my machine? I want to calculate the two angle strings and have the results range from +90 degrees to zero (at perpendicular to XY plane) to -90. I know this will not allow me to compute the 3D position, I only need the vector direction to the 3D point relative to the origin.
My thoughts are to create a unit vector from origin to the 3D point, then what maybe? ARCTAN? I did this but the values go ll over the place, positive and negative, lots of discontinuities. I need the angle values to be continuous from horizon (+90) thru normal (0) to horizon (-90) in the XZ and YZ planes. I can try to explain it further but it is hard... Most time a pair of angles to denote a direction to a 3D point is Azimuth (from North) and Elevation (from horizon), as in demarking a star location form a given point on earth. This is different as I can measure elevation in two orthogonal planes to get the complete direction description from the origin of a GCS to a 3D point. At least I think this will be enough information to do so. Please help

[hrlngrv]

So you want 2 angles defined by the triplets of points (x,0,0),(0,0,0),(x,0,z) and (0,y,0),(0,0,0),(0,y,z)? If so, I believe they'd be =DEGREES(ATAN2(ABS(x),z)) and =DEGREES(ATAN2(ABS(y),z)).

[masterjebbi]

This is great! Use ATAN2 thank you hrlgrv.
By taking the ABS am I throwing away a part of the information? I posted that I need the angle as it ranges from +90 to -90 passing through zero at perpendicular, but I can also use values that run from 0 to 180 (horizontal to horizontal) with 90 at perpendicular to my measurement plane (XY), in both X plane and the Y plane. I need to denote the dead reckoning direction to the 3D point like I am aiming a laser pointer at it from the origin 0,0,0. I am Google searching how to represent a triplet of points, as I do not understand what that means exactly. But I will try to figure it out asap. It seems logical that yes I am looking for the x to origin via xz, and y to origin via yz.

[masterjebbi]

maybe I can add an if statement, if x<0 multiply result by -1 ?
Or take out the ABS and the numbers run from zero to 180. Is that correct?

[hrlngrv]

The ATAN2 function returns values from +180 to -180 (radians converted to degrees). My interpretation of your specs was that you're mainly interested in the angle made by the z coordinate from the XY plane as measured against the x and y coordinates separately. If so, only the sign of the z coordinate should matter.

[masterjebbi]

I see, yes +180 to -180 with zero being the +X direction for one component and +Y for the other. This makes the angle hit 90 when it is normal to the XY plane in the X measurement and Y measurement.
I need to report the "firing solution" for what we will call my laser pointer toward a unique 3D point from the origin to that point as two orthogonal rise angles. I think since this construct is an analog of a device I am trying to describe (rather abstractly... apologies for that) I may be having trouble articulating myself so thank you for your patience. One piece of information I can describe is that there will never be a -Z, as that would be below the horizon and this is a "line-of-sight" operational system.
Both rise angles will be between 0 and 90 if the 3d point is in Quadrant 1, I will have an X between 90 and 180 and a Y between 0 and 90 when the 3D point is in Quadrent 2 and so on
90<X<180 , 90<y<180, point is in Q3
0<x<90, 90<y<180 point is in Q4

[masterjebbi]

after giving it some more thought, my 2 angle numbers will each depart from zero as normal in the plus and minus direction -X=-90, +X=+90 and -Y=-90, +Y=+90 as my device measures photo differentials and a 3D point overhead gives a zero differential. These differential increase as the departure form overhead (normal) increases in either the positive or negative direction.
Thank you so much for your help and in forcing me to think through this more thoroughly.
I will change some signs and add or subtract 90 properly to make my two angle time series reflect what my photodiodes will be measuring.