The images that you can find on this page are recognized draft sketches, ideas, and ways of occupying space with the first flashes of Canaletto's imagination.
In these first drafts, he was very likely jotting down ideas and checking if there could be potential for making a painting, and checking out the symmetries on the final composition, and how buildings would fill up the space and show their personalities, or gain one.
Most of these sketches come from real Venetian views, while others are unrefined first drafts for future Capricci paintings.
As much as Venice offers important scenery spots that could delight Canaletto's public, looking for new ones was definitely something he was always putting in his paintings.
Some other "commercial" painters basically replicated over and over the most successful images that tourists went for, and were happy to buy.
Giovanni Paolo Panini (or Pannini) (1691-1765) was almost a Canaletto's contemporary, and can be considered a clear example of this working/business approach.
It is very likely that Canaletto got in touch with him during his stays in Rome (1716 & 1719-20) when he was a young boy painting Theatre Sceneries with his father Bernardo.
We also have to consider that all oil paintings were done - by Canaletto - in his studio, so the production process started, most of the time, with a first draft sketch, very likely developed into a more precise drawing, and then going for the final painting work: nothing new, as a working method.
In some of these sketches we sometimes find notes for the preparation of the painting work: colors, (G for Giallo, Yellow - R for Rosso , Red, for example) or location of the sun reflection, or the name of the place that would very likely become the name of the painting itself.