A nadir frame is taken with the camera looking vertically downwards at the spot where the tripod was positioned when the other images were captured. This is done to facilitate the process of removing tripod legs from the lower row of images. It is inevitable that some unwanted elements of equipment will be captured in images, if only in the lower elevation row. In some cases, where a bland or relatively featureless surface is underfoot, it may be possible to edit unwanted elements out of the images without using a nadir image, but it is always safer to have one available in case editing difficulties arise. In environments featuring significant relief or detail, a nadir image is essential.
A number of difficulties arise when photographing a nadir image. The first of these is that the process of positioning a tripod and walking in a circle as the camera is rotated may cause significant damage to the nadir area. Grass or flowers may be trampled, and footmarks may be left in sand, snow or other soft surfaces. Where this is a potential problem, take the nadir image before attempting to acquire the others.
There are several ways in which a nadir image can be created. However, it is important to keep the nodal point of the lens as close as possible to the position it occupied, or will occupy, when other images are acquired. Some tripods are equipped with an extending boom that can be used to pull the tripod legs back from the nadir point, although such arrangements may have to be manually stabilized. Another approach is to hold an extended tripod horizontally, and at arms length. This approach gives an unobstructed view of the nadir area but it is difficult to keep the camera in the correct location. Note that a nadir area featuring significant relief and detail requires greater accuracy in maintaining the position of the nodal point of the lens.