How many degrees are in a Chicago city block
REAL SHORT ANSWER : Like most things in life, it depends.
SHORT ANSWER:
For a NS street (a street running north-south), there are about .001831 degrees in a standard city block. For an EW street (east-west), there are about .002438 degrees in a standard city block.
LONG ANSWER:
I was working on a project where I had a number of locations to show on a map, and due to privacy concerns, I wanted to jitter (slightly move) each location so it would not be readily identifiable.
As each location was identified by a latitude and longitude, I decided a good way to achieve the jitter was to add (or subtract) a small random amount to the latitude and/or longitude of a location. Now it was left to determine what the range of that random number should be. I decided I wanted everything to move at least a quarter block but no more than a half block. For the project at hand, this was sufficient to achieve the goals.
As the goal now was to determine the range of the random number to add to either the latitude or longitude, it remained to determine how many degrees are in a city block and then use this to jitter a location anywhere from 1/4 to 1/2 of a block in either direction.
A LITTLE ABOUT CHICAGO STREETS
When I gave my very short answer above, I said the answer depends. First a little about Chicago streets (all of the following is generally true, and reasonable enough for the accuracy I was trying to attain). Chicago streets are laid out on a grid. Streets that run North-South on the grid are parallel to longitude lines of the Earth and the East-West streets are parallel to latitude lines. Another fact to note ,Chicago streets are numbered in the hundreds and an 800 difference on the streets corresponds to a mile of distance on a straight street (one that is “on the grid” and doesn’t run at an angle to the grid). City blocks are usually determined by intersections, but generally 8 standard blocks make up a mile.
FUN FACT: if a street is 3200 North, you can tell a Chicagoan because they will say it is “32 hundred north” (rather than “3 thousand 2 hundred north). A hardcore Chicagoan is likely to tell you it’s “32 hunnert north”
See hear for a little more detail on the grid system
https://en.wikipedia.org/wiki/Roads_and_expressways_in_Chicago
So the basic approach then is to take two streets that are on the grid a mile apart and calculate their corresponding longitude or latitude (depending on whether it is a NS or EW street) and then calculate the difference, which would be the degrees in a mile. Then the degrees in a standard block could be determined by dividing this by 8.
So where does the “it depends” come in ? Recall that NS streets parallel longitude lines and EW streets parallel latitude lines. Longitude lines by definition all go through the poles, so every longitude circle (actually ellipse) is the same diameter. So a mile anywhere on any longitude line is the same number of degrees. A mile along a longitude line in Chicago will have the same number of degrees as a mile along a longitude line in Quito, Ecuador as well as the same number of degrees as a mile in Sydney. Australia.
But this is NOT the case of latitude.As you go move above (or below) the equator towards the poles, circles of latitude get progressively smaller in diameter (while still comprising the same 360 degrees). So there will be MORE degrees in a mile the further from the equator (and thus nearer a pole) you go. So the number of degrees in a mile on a latitude line in Chicago is NOT the same as one in Quito.
So I can probably Google the degrees in a longitude mile, and thus divide this by 8 and get the number of degrees in a NS Chicago city block. The EW streets (corresponding to latitude lines) are going to take a little more work. To simplify this process, I’m not interesting in being exceedingly exact. Even though an EW street on the far North side might have slightly more degrees than an EW street on the far South side of the city, I want just one number for the entire city. So I’ll take a sampling of a number of pairs of street (each pair a mile apart on the grid), and just average the differences.
Here’s an example of a calculation in the Central area , using Google Maps. Travelling on Madison from East to West, the distance from Madison and Cicero to Madison and Central is 1 mile by the convention mentioned above (4800 West to 5600 West is 1 mile). Google Maps gives the locations of those two corners as
Madison and Cicero … 41.880491, -87.745268
Madison and Central ..41.880305, -87.764857
These are approximate and not exact. Note the slight difference in latitudes which if we could measure exactly we would expect to be the same. In any case, the difference in the two longitudes is .019589 degrees for the mile (and divide that answer by 8 for the degrees in a block). We can continue this process and average to get a reasonably approximate answer to our question which is listed above in the “Short Answer” section.