Another way of satisfying Guideline 1 (keeping the angles between the photographs close to right angles) is to separate the Camera Stations not only horizontally, as shown in the previous figures in this chapter, but to separate them vertically also. Two cameras can have right angles between their views in any three dimensional orientation. The Camera Stations do not need to be all at one level.
The figure below is a somewhat extreme example of this. In this figure a tall building is being measured. All the photographs could be taken from the ground, but the points along the roof line would be very far away from the ground level photographs, and hence would be harder to mark (because they would be smaller in the photographs than points along the ground). This would make the roof top points less accurate than the ground level points. The ideal solution would be to take some photographs from above the building. This could be done if there were adjacent buildings that were taller, or if an airplane or helicopter was used. In this case the Camera Stations above the building, and at ground level on one side of the building, are close to being 90 apart.
Positioning Camera Stations for a Tall Object
Guideline 3: Try to take photographs with good vertical and horizontal separation. Try to surround the object of interest and try to get above and below it.