I like maps, I always have. I could spend hours looking at and reading maps, which is maybe the reason that I am fascinated by this one. All I know is I couldn't have planned most of my walks through Brooklyn without it, or figured out so easily where I'd been when I got home.
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With a couple of clicks of the mouse you can go from a view of all five boroughs down to a view of one block and all the building lots and buildings on that block.
You can chose a traditional two dimensional map view or a photographic aerial view.
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When you are at the building/building lot level you can choose the "i" icon and click on a building and a window will pop up giving you all the information on that building including the square footage, number of floors, owner, date of construction, the zoning map it appears on, etc.
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And what has become a very valuable tool for my own walks, you can calculate distance from one point to any other point along the map.
A couple of caveats: I am not sure all the building construction dates are absolutely accurate; some of them don't jibe with dates I happen to know. Also, lately it hasn't been working too well with Firefox, or at least with my Firefox application, and I have had to open it in Explorer.
That much said, it is really a wonderful map and I have suggested to the DoITT that it should not be buried so deep in the city web site but should be linked to on the nyc.gov home page.