The "world" (camera) space coordinates can be computed directly from pixel space as follows:
X = (Xpixel - Cx) / Fx * Z
Y = (Ypixel - Cy) / Fy * Z
Cx, Cy is usually around half of the image resolution, for example, if the image is 640 x 480, Cx is around 320, Cy is around 240, +/- 10 pixels
Fx and Fy is usually the same or very close for the Astra S cameras, and Fx = Fy = 575 for depth, and Fx = Fy = 520 for video.