How I map race circuits step by step, so my layouts actually look right

I came at it from the opposite end for ages, sketching layouts from memory first, then wondering why Mugello looked like a squashed banana compared to the real thing. Tracing over a printed map fixed that for me too, though I do it old school with a lightbox and pencil before scanning it in. The scale part is where I always came unstuck untill I started using the straight between two markers I coud actually verify on the map, rather than trusting the overall length alone. One thing I'd add on the corner numbers is that apex placement changes depending on which class you're watching. I once marked a fast line through the penultimate turn at Assen from a Moto2 onboard and when I checked a slower reference it read totally differently. Now I pick one lap video per circuit and stay with it all the way through so the numbering stays consistent. The one circuit per sheet rule is so true. I had a spread with Qatar and Losail details bleeding into my Portugal sheet and spent an evening unpicking it. I also started writing the length at the bottom in pencil first, then inking it, which sounds fussy but has saved me a few redraws after spotting a mistake too late.

I tried this after seeing a race on TV last season and my version of one of the Spanish tracks came out with a loop in the middle that doesn't exist in real life. Turns out I was drawing the shape from how it looks on the TV camera angle, not how it actually is. When you trace over the map, do you use an aerial photo or is there some special kind of circuit map I shold be looking for?

For me the game changer was a pad of tracing paper I picked up from an art shop for a couple of quid. I tape it over the tablet or printout, draw the outline in soft pencil, then flip it over and draw the same shape again to catch where I've drifted. Sounds daft but it exposes every wobble in your line instantly.

On the map source question from earlier, I use the venue's own circuit map from their website as the base, then cross check the tricky bits against satellite view, because those promotional maps sometimes simplify the realy tight corners.

Update: tried that trick from the tracing paper reply, drawing the outline again flipped over to catch drift. It found a kink on my straight at one circuit that I'd been staring at for weeks without noticing. Question though, when you flip it and trace back over, do you correct the original or keep both versions and pick the cleaner one? Mine ended up slightly diferent shapes each way.