I am currently developing a map series using ArcPy with ArcGIS Pro. I am not using the Map Series functionality for this because I need to have lots of control over what is on each map sheet, and there are many exceptions to its many rules. Instead of using Map Series functionality I am simply using a search cursor to iterate through the map series index and setting the camera extent of the map frame to each map sheet.
For each map frame only one of three map frames is visible, because there is a map frame for each of the UTM/MGA zones in my "third" of Australia. I use the mean of xMin and xMax of each sheet extent to decide which zone I am in and choose the appropriate map frame to use.
I am using 30 minute (half degree) square map sheets in GDA94, and drawing them in a projected MGA Zone which means they are no longer quite square and depending on where each sheet is in the zone that almost square may be "rotated" slightly. My understanding is that cartographers will usually "straighten" up the map by rotating it slightly. Often this is done by eye but my understanding is that there is a formula that can be used to calculate the amount of rotation that is needed to make each sheet look straight. An example rotation value is `-0.0782913899729035.
Is anyone familiar with the formula that I am trying to describe and able to point me at where I may be able to find details of it for Australia (MGA zones) or globally (UTM zones)?