The angular distance between the Horizon and vVP is 90°. The truck cab and the first lamp post are about in the perpendicular direction of the driving road direction, as we notice from the aligned two lamps at the top and the truck's viewed perspective (see the 90° turned camera view at the same place and time). This gives a 90° reference in the photo on the Horizon line. It allows evaluating FOV ~ 145° (*).

(*) However, this photo is not good enough for a precise evaluation. Analysis of the context is always necessary prior to calculations. The strong wide-angle makes the estimation sensitive to small errors. The actual Horizon Line is slightly above because the road goes down towards the horizon. The speedy moving camera and the interpolation process to reproduce a planar photo from a panoramic distorted shot, may introduce some positioning errors in the Center of View C and in the first lamp post and its verticality. See corrected simulation results below. FOV seems to be ~148° and vVP and the Horizon are a bit higher.

1) Take a sufficiently good photo (*). The best images exhibit sharp sun shadows, vertical and horizontal lines, vanishing directions, horizontal planes, etc. Get as much information as possible from the camera: focal distance or the field of view, pitch and roll angles, etc. Use normal lenses without special effects (like fisheye or strong wide-angle lenses, etc.).

(*) The example photo was computer-generated by Blender® with a focal length = 20 mm, a solar elevation of 30°, and an azimuth of 140° relative to the viewing direction.

2) Estimate the Vanishing Point VP of the solar rays from their reflections, shadows, or shades. The ideal would be to have some light probe in the photographed scene. If the sun is photographed in the frame, VP is simply the center of the sun. Otherwise, the simplest method is to analyze cast shadows. Best estimates come from sharp long and sufficiently separated shadows. In this example, VP is the anti-solar point. 

3) Estimate the Horizon line H of the scene. If the camera is leveled this line will appear as horizontal i.e. parallel to the left/right axis. Vertical lines may help find the direction if the camera is right or left tilted (with some roll angle).  If the camera is forward or backward tilted (with some pitch angle), the vertical lines are not parallel but converge to some vanishing point (In the figure vertical lines point to some far point below).

4) Estimate the Center of View C of the camera. It is the point in the photo where the camera is pointing to. Normally it is located at the center of the photograph if this has not been cropped, and if the lens is centered without artifacts (as with shift or tilt lenses). With a zero pitch angle, C is located on the Horizon line H. A forward tilt gives C below H as in the figure.

5) The value of the camera's Focal distance FD determines the angle of the camera's Field of view FOV. Knowing the positions of H and C it is possible to draw the spherical coordinate projections superimposed on the photo centered on Hc, the Horizon center. Set FD so that the projected vertical direction of the posts fits the verticals of the spherical frame. As FD = 18/tang(FOV/2), the horizontal of our example at C gives FOV=84° (from -42° to +42°), so FD=20 mm.