User:Bubba73/sandbox


 * $$3x \equiv 1 \mod 20$$
 * $$7y \equiv 2 \mod 20$$
 * $$11x \equiv 3 \mod 20$$



$$ C = k \cdot \epsilon_0 \cdot A / d $$

2/sup3 45

$$2^3$$

$$2/sup3 45$$

Coordinate errors
Over the past couple of weeks, I've corrected probably a few dozen coordinates of NRHP sites by finding the building using ACME Mapper and reading off the actual coordinates. (I'm assuming that ACME Mapper is accurate - it agrees precisely with Google Maps.) Anyhow, when the coordinates are given in decimal degrees, almost always everything after the third digit after the decimal point is wrong, and when they are given in D/M/S, they are no better.

Here is an example, from National Register of Historic Places listings in Effingham County, Georgia, the jail. The NRHP form is from 2006, so it should have recent (accurate) data. It gives the UTM of zone 17, easting 470266 Northing 3581760. It looks like it might be accurate to within a meter.

Using this to convert to degrees, it gives 32.37241°N, -81.31608°W. The page lists 32.374167N, 81.316111W. Notice that everything past the third digit after the decimal point is wrong, which is typical in the ones I've examined. In this case, the north coordinate is off by 0.00175+, which seems to be larger than typical.

So the first point is that the coordinates given in most places do not agree with the conversion from the NRHP forms after the third digit after the decimal point, which is enough to throw them off a block or two. I suspect that when these were converted from the UTM on the NRHP form, the conversion wasn't done correctly. (I don't know who did these or when.) Does anyone know details about how these conversions were done?

The second point is that the NRHP UTMs are quite a bit off, assuming that the conversion website above and ACME Mapper are accurate. The coordinates given on the NRHP form, converted to degrees, puts the jail out in the woods, whereas I think the center of the building is actually at 32.37413°N, -81.3157°W. Using the conversion website, that gives UTM zone 17, easting 470302 northing 3581950 - a difference of 36 meters E/W and 190 meters N/S. (The courthouse is off even more, but its NRHP form seems to be rounded to 100 meters.)

examples

 * National Register of Historic Places listings in Wilkinson County, Georgia, the Elam-camp house. The 1982 form says: zone 17, easting:281380 northing: 3640560.  This converts to 32.8814°N, -83.3369°W.  The county article had 32.88306°N, -83.33694°W.  The actual location (from ACME mapper): 32.88333°N, -83.33679°W.  The difference N/S is 0.00166 degrees, about 600 feet.
 * National Register of Historic Places listings in Effingham County, Georgia - the jail. The 2006 form says: zone 17, easting 470266 Northing 3581760.  That is 32.37241°N, -81.31608°W, the article gives: 32.37417°N, -81.31611°W, off by off by 0.00175 degrees N/S (over 600 feet).


 * National Register of Historic Places listings in Wheeler County, Georgia, the courthouse. The 1980 form: zone 17, E: 331900, N: 3558080. This is 32.14663°N, -82.78239°W. The page had: 32.14778°N, -82.7825°W - 0.00115 degree off N/S, over 400 feet. (Actual: 32.14813°N, -82.7823°W.)

I don't know what the cause of the errors is. If they used the old datum, the N/S error should be about 100 feet, but these are several hundred feet off in N/S, and the UTM on the forms is south of what it should be (by several hundred feet). But by 2006 (the second example), they should be using good maps. In these cases, the old lat/long coordinates in these three articles are more accurate than the UTM from the forms, so the problem may not be in the conversion from UTM to lat/long, as I thought. But I don't understand where the error is. Bubba73 You talkin' to me? 00:52, 6 November 2015 (UTC)


 * Wormsloe 31.98369°N, -81.07179°W
 * 31.98111°N, -81.08333°W
 * 31.94889°N, -81.0575°W
 * 32.87861°N, -82.08333°W

Q&P endgame
This is usually a win for the two pawns, but there are a number of exceptions, most notably with connected rook and knight pawns (g- & h-pawns or a- & b-pawns). Victory can be difficult to achieve even in winning positions as even the slightest inaccuracy may lead to perpetual check as queens roam a nearly empty board. Draws are easier to secure if the defending king is ahead of the advancing pawns, and if both pawns are not within two squares of promotion.

Positions in which one of the pawns is vulnerable to attack may be drawn, but they are unusual.

Connected knight pawn and rook pawns draw if the defending king is in front of them. An example game is Smbat Lputian vs. Gevorg Haroutjunian, 2001. The position after 86.h6 is a draw. After much maneuvering, the position after 125.Kh4 is also a draw, even with White's favorable position and advanced pawns, but then Black made a losing move 125...Qf7? Inaccuracies on both sides caused the position to go from a win to a draw a few times. The position was a draw before Black blundered on move 141 and he resigned on move 142. Interestingly, Black could have claimed a draw by the fifty-move rule for the last several moves, including the position in which he resigned, but he did not.