I just finished another waterpark cartoon map. I probably have an advantage in this genre in that my degree is in architecture. So, when clients supply reference for a project, I have experience in interpreting the architect's plans into 3D. Of course, I'm doing it in exaggerated fashion to make a fun presentation.
There is an incredible amount of detail that goes into these projects. Many cartoonists are accustomed to working in minimalist styles. It takes a special patience to do this type of work.
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When clients furnish photos of an existing park for reference, it's funny how sometimes they will send me the exact opposite side of a view from what I'm drawing. I guess since they are so familiar with their park, they think the most common view from the sidewalk is what I need to work from. But if I have to draw the south side of a building and they've given me the north side, I can't just make up what the other side looks like! Same with rooftops. Lots of times I'm furnished with a pedestrian view of a building that doesn't show the roof. And I'm typically drawing a bird's eye view with these maps. So I have no idea what to indicate for the rooftop!
Thankfully, Google Earth is making my work easier these days with updated aerial photos of most places in the world. I can check out most of these places and, if the resolution is high enough, see a lot of the details the clients may not have on hand.