Barometer - Revision history

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Use

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{{Item
| name = Barometer
| image = Barometer.png
| weight = 1
| bulk = 1
}}

A '''barometer''' is a device that gauges atmospheric pressure. It is used in Egypt to measure the altitude at the holder's location. Knowing your altitude is crucial to properly mixing a [[Test of the Ritual Tattoo|Ritual Tattoo]], and is also helpful in planning [[Aqueduct]] routes.

==Sources==

Made in a [[Glory Hole]].
Menu options: Start Making > Special Projects (add spheres from the highest quality to lowest).

This item becomes available once you have begun the [[Test of the Ritual Tattoo]].

==Cost==
*1 [[requires::Glass Pipe]]
*1 [[requires::Lead]]
*1 [[requires::Water]]
*3 [[requires::Barometric Sphere]]s.

==Notes==
Barometers, like other crafted tools, have a [[quality]] associated with them. A higher quality barometer is more accurate.

Final quality of a Barometer can be determined by doing the following formulas: Average = FLOOR((A + B + C) / 3).<br>
Final quality = Average - ABS(Average - A) - ABS(Average - B) - ABS(Average - C)<br>
Where A, B and C are the quality of the [[Barometric Sphere]]s

==Use==
When carried, a new menu option becomes available under Special > Measure Altitude. This immediately reports the altitude of your current location in Main, in feet and inches.

Typical altitudes are 0 (sea level) - 600 feet (top of a tall 'mountain')
1 7000+ Quality needed for charcoal brazier.

==Research and Tuition==
*''150 7000+ Quality required for [[Automatic Charcoal Production]] research''

==Accuracy==

[[Image:Q1940Barometer.png|thumb|300px|Data for a quality 1940 barometer]]

As in previous tales, barometers appear to report an altitude that varies according to the in-game time of day and the quality of the barometer.

The reported reading is the true altitude, plus or minus an error that follows a sine wave over the course of the game day:

t = (Egypt minutes since midnight) / (24*60)
reported altitude = true altitude + E * sin(2*pi*t)

E is the maximum error of the barometer, which depends in some (currently unknown) way on the barometer's quality. E is smaller for higher quality barometers.

All barometers are perfectly accurate at 12AM and 12PM gametime (sin(0) = sin(pi) = 0), and are most inaccurate at 6AM (too high by E inches) and 6PM (too low by E inches).

===Determining E===

You can find E for a given barometer by measuring the altitude of '''exactly''' the same spot at 6AM gametime, then again at 6PM gametime. Convert the readings to inches, then:

E = ((reading at 6AM) - (reading at 6PM)) / 2

It's best to use a flat area with an obvious marker to stand at, so that you can be sure you're measuring at the same spot each time.

Make sure your test spot is at least 10 feet above sea level, you don't want either reading to be 0.

===Quality vs E===

{| border="1" cellspacing="0" cellpadding="5"
! Quality !! 6AM reading !! 6PM reading !! E (inches) !! Notes
|-
| 1 || ? || ? || 60 || from the T2 wiki
|-
| 1940 || 41' 10" (502 inches) || 33' 0" (396 inches) || 53 || T4 verified
|-
| 3734 || 73' 0" (864 inches) || 65' 1" (781 inches) || 47.5 || T4 verified
|-
| 6517 || 72' 0" (864 inches) || 66' 1" (793 inches) || 35.5 || T4 verified
|-
| 8007 || 71' 3" (855 inches) || 66' 10" (802 inches) || 26.5 || T4 verified
|}

[[Category:Resources]]

{{L|en}}

@@ Line 24: / Line 24: @@
 Barometers, like other crafted tools, have a [[quality]] associated with them. A higher quality barometer is more accurate.
- Final quality = The lowest quality of the three spheres, then subtract the difference in quality from that one to the other two, which means that if you add a high quality sphere to two low quality ones, you will get something really, really bad (down to q1 maybe). Keep all three as tight as possible in quality, and you'll end up with a result slightly lower than the lowest of the three.
+When combining three barometric spheres of exactly the same quality, the resulting barometer will have exactly that quality too. When combining spheres of different qualities, the barometer will get a resulting quality that is lower than the lowest of the three, according to this formula:
-Another way of putting it, which might fool you to think that the "average" is useful (it's a distraction here):
+ Sort the three qualities, so "Q1" is the lowest and the other two are "Q2" and "Q3". Then the resulting quality, "BQ", will be as follows:
-Final quality of a Barometer can be determined by doing the following formulas: Average = FLOOR((A + B + C) / 3).<br>
+ BQ = 3 * Q1 - Q1 - Q2 - Q3
-Final quality = Average - ABS(Average - A) - ABS(Average - B) - ABS(Average - C)<br>
+or simplified:
-Where A, B and C are the quality of the [[Barometric Sphere]]s
+ BQ = 2 * Q1 - Q2 - Q3
-'''NOTE''': You '''SHOULD''' use 3 barometric spheres close in quality.  The formula above uses the word average a lot, but your final result will '''NOT''' be an average, it will be lower than the lowest of the three, the closer the three are, the less you'll lose in total quality!
+'''NOTE''': You '''SHOULD''' use 3 barometric spheres close in quality.  Your final result will '''NOT''' be an average, it will be lower than the lowest of the three sqheres, the closer the three are, the less you'll lose in total quality!
 ==Use==