Traditional photogrammetric triangulation packages do not have a group layer. In other words, a set of images are associated with a frame which, with other frames and their images, are associated with a camera. Suppose, however, that for the same camera, two sets of frames were taken, one before and one after the camera was calibrated. The first set of frames would be associated with some previous calibration, while the second set with the recent calibration. Alternatively, suppose that the first set of frames was taken with kinematic GPS support on the aircraft and, due to, say, a malfunction, the second set of frames did not have kinematic GPS support. Both of these examples illustrate that a specific camera has dynamic attributes that need to be taken rigorously into account during the triangulation adjustment. Other instances that might warrant the use of frame groups could include moving the camera between different aircraft where environmental conditions may vary, changing film types or changing the camera's lens. The user can draw other dynamic camera attributes from his own experience that may want to be discriminated in the triangulation. GIANT's groups feature enable this flexible data associativity.

 Notice that the Group Parameters screen has the following features:

 As with the camera systems, the logical progression of group functions would be: Add one or more groups, Modify any group found to be incorrect or inappropriate, Delete a Group which is no longer needed or pertinent. The discussion will follow this sequence. The Close button exits the group management function.

 Group management naturally begins with the definition of groups. Assign a name to a group by using the mouse to activate the Photo Group window. Key in the group's name. Alphabetic, numeric and special characters are allowed. As a general (and, hopefully, obvious) piece of advice, the group name should be as descriptive as possible: CAL12_95 offers more clarity than, say, GROUP_1 or GROUP_A. As the number of groups grows, movement between the different groups is most easily achieved with the down arrow, found to the right of the Photo Group window. Pressing it with the mouse will produce the drop-down list of all group names, from which the desired group may be selected through the customary Windows double-click selection actions.

As with the Camera Management option, the Group Management option permits a specification of standard deviations to be assigned to each frame position and orientation and image associated with the group. These values are stored in the Default Standard Deviations table. Use the mouse to select a field and key in an appropriate standard deviation for each entry of the table. As always, remember that the standard deviation is a measure or estimate of uncertainty in a parameter. The larger the uncertainty of a parameter, as indicated by its standard deviation, the less influence the parameter will have on the adjustment. Fidelity of the adjustment relies on realistic standard deviation assignments.

When values for the three components, their standard deviations and the Adjust and Modify switches have been set appropriately, return to the main Group Parameters screen by clicking on the Photo Groups tab at the top of the display.

 Back at the main Photo Groups screen, when information has been supplied for all of the tables, windows and switches, use the mouse to press the Add button to add the group to the Group Definitions file. Confirmation that the group definition was in fact saved may be obtained by re-visiting the Photo Group field. Click on the arrow icon to its right to produce the list of group definitions, and confirm the latest addition.

 In the same manner, any number of group definitions may be added to the Group Definition file. Suppose that the Group Definition file contains the definitions of 3 groups: when the list arrow is pushed, three group names appear in the list. Suppose, now, that one group has incorrectly specified the default x image standard deviation to be 50 micrometers, instead of 5. The value must be edited. Group definition editing is implemented through the Modify button. To modify a group definition, first use the list feature of the Photo Groups field to list all the group definitions in the file. Select the group with the incorrect default x standard deviation. The main Photo Groups screen will refresh with the currently-stored values of the parameters. (As a matter of fact, the background GPS Parameters screen that is not displayed has also had its parameters updated.) Modify the default x image standard deviation by keying in the correct value in the Default Standard Deviations table. To complete the operation and store the edited parameter values in the Group Definition File, select the Modify button. Any parameter on any of the group management screens can be modified in this manner.