How is zoning done for an irregular plot?
The method is the same. Take the degree of one wall on Google Earth, draw a line through the centre parallel to that wall, set off the tilt (for example 20 degrees towards West, that is 340 degrees) to get exact North, align N5 of the chakra with it and mark the zones. The centre of an irregular plot can be found only with AutoCAD or by cutting the paper plan to shape and finding its balancing centre.
Related questions
If the built-up area is on one side, such as South and West, with the other sides open, how are the pishach bhoomi and devtas found?
Use the angular method taught in class. Whatever the tilt and whatever the shape, octagonal, pentagonal or regular, find the centre, divide the plan into pishach, manushya-dev and brahma bhoomi and mark the pads by degrees as demonstrated, then practise it from the recording.
If Google Earth shows 350 degrees, how should North be marked on the plan?
In a regular plot you can set the zero directly at 350 degrees when drawing the straight line. It is easier to think of it as a 10-degree tilt and set off 10 degrees, because that method works from whichever side of the plot you start.
My compass showed North tilted toward the North-East, and Google Earth showed 2.39 degrees. Is that also toward the North-East?
Not necessarily. A magnetic compass shows North directly, so its reading can be stated straight away, for example North 30 degrees toward East. Google Earth and the mobile app only show the heading of the line you draw, and North has to be worked out from it; a heading of 2.39 means North lies 2.39 degrees to the left.
Should directions now always be read by degrees?
Yes, always by degrees; reading directions without degrees was a mistake, and only the degree method shows the actual zones.
Why does each outer devta cover 11.25 degrees, and how are the pads marked?
The 32 devtas of the pishach bhoomi share the full 360 degrees, and 360 divided by 32 is 11.25. Mark North with the plot's actual tilt (for example 5 degrees), place Som devta centred on North with 5.625 degrees on each side, then mark every further 11.25 degrees with a protractor or a zoning chakra and draw those lines only in the outer ring. The 12 inner devtas follow an 18-54-18 degree split in each direction (27 degrees on each side of the direction line for the middle one), and Brahma sits in the centre.
Will every map have a 10-degree tilt with North at the top?
No. Each map has its own tilt, 10, 12, 20 or 25 degrees, and North can be on any side. Measure the tilt with Google Earth and find which side is North at the site, from the client or from the North mark that most plans carry, although the tilt itself is not written on them.