Wikipedia:Reference desk/Archives/Miscellaneous/2023 July 17

= July 17 =

Where can I find information about the land use history of the Chicago metropolitan area?
Specifically, I'm looking for information on what the lands that are now part of forest/nature reserves were used for prior to their establishment as reserves. ZFT (talk) 04:43, 17 July 2023 (UTC)
 * Here is some information from the Forest Preserve District of Cook County which may lead you to interesting places. There are a number of documents linked from that overview history page.  If, after exploring all of those documents, you cannot find what you are looking for, this page has some contact information you may be able to use to reach out to the Forest Preserve District and someone there may be able to direct you to the information you seek.  -- Jayron 32 10:59, 17 July 2023 (UTC)

Underwater objects
Earlier today, I had occasion to look at the Google Maps aerial view of an area near Valletta, Malta. At 35.8883°N, 14.513°W, in the Grand Harbour near the mouth of French Creek, there appear to be two almost parallel objects under the water. The one on the left, especially, with its "prow" at the southern end, gives the impression of being a ship, but I find it hard to believe that two sunken ships would happen to be so aligned or that they would be left in shallow waters where they would constitute a hazard to navigation. Does anyone have an idea what these things might be? Deor (talk) 22:55, 17 July 2023 (UTC)
 * I believe they're ghosts created by a data processing glitch.
 * Google Maps is created by combining several different sets of photographs taken during multiple flybys of planes and/or satellites. Probably those ships were present during some of those flybys, but not present during other flybys, and the algorithm did its best to piece together the two conflicting pieces of information.
 * Whatever algorithm they use is pretty good at filtering out moving cars, but perhaps it wasn't prepared to identify a vehicle this big. ApLundell (talk) 23:43, 17 July 2023 (UTC)
 * Hmm, you may be right. Here's another example in Valletta, and there's some sort of weird "double exposure" effect immediately to the southwest of this one. Deor (talk) 00:08, 18 July 2023 (UTC)
 * And in this aerial view of Monroe Harbor in Chicago, almost all of the small sailboats present the same "sunken" appearance. I spend a good deal of time looking at Google Maps (though not usually for boats), and I'm surprised that I've never noticed this before. Deor (talk) 00:20, 18 July 2023 (UTC)
 * But why do they have to combine several photographs taken at different times? Why can't they just take one photo and use that? --Viennese Waltz 07:09, 18 July 2023 (UTC)
 * To take just one picture the camera has to be higher up. As cameras have finite resolution and atmospheric distortions will increase, that would give lower quality and resolution. The highest resolution pictures you see on Google Maps are taken from no more than 1500 feet. PiusImpavidus (talk) 09:13, 18 July 2023 (UTC)


 * The east ghost ship (along with its two ghost tugs) isn't very clear, the one on the west (also with two ghost tugs) seems to be the same ship as the one docked half a kilometre to the south, with one of the tugs still present. The blue area near the bow is quite distinctive. PiusImpavidus (talk) 09:13, 18 July 2023 (UTC)