Every chapter names the part of your chart it came from, so you can check the work against any free bodygraph.
Two moments are read: the minute you were born, and the moment the Sun stood eighty eight degrees of arc earlier, which is the design side of the chart. For each we compute thirteen positions and convert them to gates and lines on the sixty four gate wheel, where gate 41 opens at two degrees of Aquarius and each gate spans 5.625 degrees.
Positions come from astronomy-engine, an open implementation of the JPL planetary model. Your birth city is resolved to coordinates and to the time zone in force on that date, so historical clock changes land on the right instant.
Gates become channels, channels define centers, and the defined centers give the type and the authority. Nothing is guessed. Where a birth time is missing we say so on the page instead of inventing one.