The method shown here is by far the best way to draw accurately and in proportion.
Over the years I have taught many students, at all levels, how to draw in proportion. This is essential if you want to draw and paint to your full potential. You won't paint well until you are able to draw accurately. You will simply be painting on a badly drawn composition. This quickly leads to frustration and many people give-up at this stage because they cannot achieve the image they have in their head, or it doesn't look like the photo they might be copying from.