When making a sketch of an object what proportions are used?

so, not gonna do the actual thing because that's just laziness for an easy assignment like this.

but someone that has a lot of information and interesting details about is picasso. you can easily write a 500 word essay about him and how overtime his paintings of himself got more and more deformed representing that he was forgetting what he looked like and that was from memory.

based on the images pictured above, the major difference between the two cathedrals: the cathedral of notre dame and the amiens cathedral, is that the cathedral of notre dame emphasizes the horizontal lines while the amiens cathedral emphasizes the vertical lines.