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Gravity, Elevation And Temperature Barometer Reading
Correction Calculator


This calculator requires the use of JavaScript enabled and capable browsers. This script determines the error in an observed barometer reading, based on gravity differences in different latitudes, barometer elevation differences from sea level, and on temperature expansion and contraction differences. Because the Earth is not a perfect sphere, the acceleration due to gravity depends on latitude. The radius of the earth is greater at the equator than at the poles. This means that gravity is least at the equator and greatest at the poles. Thus at smaller latitudes the mercury in the barometer tube weighs less, and will require a greater length to balance a given pressure. The barometer is calibrated for a latitude of 45 degrees, at sea level. For latitudes less than 45 degrees, the correction should be subtracted from the observed height; for latitudes greater than 45 degrees the correction should be added. The metal housing of the barometer and the mercury both expand as the temperature increases. However, they expand at different rates. The barometer is calibrated for 0 degrees C, at sea level. For different temperatures a correction must be applied to compensate for the different expansions of the housing and the mercury. For temperatures greater than 0 degrees C, the correction should be added to the observed height; for temperatures less than 0 degrees C, the very minor correction should be subtracted. Contraction differences are extremely small and almost negligible. For elevation, the barometer is also calibrated at sea level; the higher the elevation, the lower the pressure. With the barometer at elevations above sea level, the correction should be added since it is a negative value; below sea level, the value is also added but the value is positive. The default values are typical for the general lower desert area of Southern California. If you wish to show below sea level changes, just use a negative number for the appropriate elevation. To use the calculator, enter the temperature, the elevations, the latitude and the known and observed barometer reading, in any of the designations, then click on Calculate. Results are returned in both inches of mercury and millibars. If you don't know the latitude, you can use our USA longitude and latitude map to get an idea of the general area. There are also temperature, elevation and latitude correction charts below the calculator. Other pressure correction calculators are for temperature correction only, for altitude correction only, for gravity (latitude) correction only, for temperature and altitude correction.


Unit
Value
Required Data Entry
Latitude    degrees
Air Temperature Degrees
 °C  °F
Elevation Of Barometer ASL
 Meters  Feet
Observed Barometer Reading
 Millibars  Inches Hg
   
Calculated Results
Actual Barometer Correction inches of mercury
Rounded Barometer Correction inches of mercury
Actual Barometer Corrected inches of mercury
Rounded Barometer Corrected inches of mercury
Actual Barometer Correction millibars
Rounded Barometer Correction millibars
Actual Barometer Corrected millibars
Rounded Barometer Corrected millibars

 Correction Chart For Relative Expansion Of Mercury And Brass Scale To 32°F Standard
Temp1
°F		 Observed reading of the barometer, in inches
25 25.5 26 26.5 27 27.5 28 28.5 29 29.5 30 30.5 31.0
Correction to be subtracted from observed reading
40 .026 .026 .027 .027 .028 .028 .029 .029 .030 .030 .031 .031 .032
42 .030 .031 .032 .032 .033 .033 .034 .035 .035 .036 .036 .037 .038
44 .035 .036 .036 .037 .038 .038 .039 .040 .040 .041 .041 .042 .043
46 .039 .040 .041 .042 .043 .043 .044 .045 .046 .046 .047 .048 .049
48 .044 .045 .046 .047 .047 .048 .049 .050 .051 .052 .053 .054 .054
50 .048 .048 .050 .051 .052 .053 .054 .055 .056 .057 .058 .059 .060
52 .053 .054 .055 .056 .057 .058 .059 .060 .061 .062 .064 .065 .066
54 .057 .059 .060 .061 .062 .063 .064 .066 .067 .068 .069 .070 .071
56 .062 .063 .064 .066 .067 .068 .069 .071 .072 .073 .074 .076 .077
58 .066 .068 .069 .070 .072 .073 .074 .076 .077 .078 .080 .081 .082
60 .071 .072 .074 .075 .077 .078 .080 .081 .082 .084 .085 .087 .088
62 .076 .077 .079 .080 .082 .083 .085 .086 .088 .089 .091 .092 .094
64 .080 .082 .083 .085 .086 .088 .090 .091 .093 .095 .096 .098 .099
66 .085 .086 .088 .090 .091 .093 .095 .096 .098 .100 .101 .103 .105
68 .089 .091 .093 .094 .096 .098 .100 .102 .103 .105 .107 .109 .110
70 .094 .095 .097 .099 .101 .103 .105 .107 .109 .110 .112 .114 .116
71 .096 .098 .100 .102 .103 .105 .107 .109 .111 .113 .115 .117 .119
72 .098 .100 .102 .104 .106 .108 .110 .112 .114 .116 .118 .120 .122
73 .100 .102 .104 .106 .108 .110 .112 .115 .116 .118 .120 .122 .124
74 .103 .105 .107 .109 .111 .113 .115 .117 .119 .121 .123 .125 .127
75 .105 .107 .109 .111 .113 .115 .117 .119 .122 .124 .126 .128 .130
76 .107 .109 .111 .113 .116 .118 .120 .122 .124 .126 .128 .131 .133
77 .109 .112 .114 .116 .118 .120 .122 .125 .127 .129 .131 .133 .136
78 .112 .114 .116 .118 .120 .123 .125 .127 .129 .132 .134 .136 .138
79 .114 .116 .118 .121 .123 .125 .127 .130 .132 .134 .137 .139 .141
80 .116 .118 .121 .123 .125 .128 .130 .132 .135 .137 .139 .142 .144
81 .118 .121 .123 .125 .128 .130 .132 .135 .137 .140 .142 .144 .147
82 .121 .123 .125 .128 .130 .133 .135 .137 .140 .142 .145 .147 .149
83 .123 .125 .128 .130 .133 .135 .138 .140 .142 .145 .147 .150 .152
84 .125 .128 .130 .133 .135 .138 .140 .143 .145 .148 .150 .153 .155
85 .127 .130 .132 .135 .137 .140 .143 .145 .148 .150 .153 .155 .158
86 .130 .132 .135 .137 .140 .142 .145 .148 .150 .153 .155 .158 .161
87 .132 .134 .137 .140 .142 .145 .148 .150 .153 .155 .158 .161 .163
88 .134 .137 .139 .142 .145 .147 .150 .153 .155 .158 .161 .163 .166
89 .136 .139 .142 .144 .147 .150 .153 .155 .158 .161 .164 .166 .169
90 .138 .141 .144 .147 .150 .152 .155 .158 .161 .163 .166 .169 .172
92 .143 .146 .149 .152 .154 .157 .160 .163 .166 .169 .172 .174 .177
94 .147 .150 .153 .156 .159 .162 .165 .168 .171 .174 .177 .180 .183
96 .152 .155 .158 .161 .164 .167 .170 .173 .176 179 .182 .185 .188
98 .156 .160 .163 .166 .169 .172 .175 .178 .181 .185 .188 .191 .194
100 .161 .164 .167 .171 .174 .177 .180 .183 .187 .190 .193 .196 .200

  Note1: Temperature of the column of mercury in degrees Fahrenheit.


 Correction Of Mercurial Barometer For Latitude In Inches Hg To Reduce To 45 Degrees Latitude
To be added to barometer readings for latitudes above 45 degrees,
or subtracted from barometer readings for latitudes below 45 degrees.
Latitude Reading of the barometer, in inches
18 19 20 21 22 23 24 25 26 27 28 29 30
0 90 0.047 0.049 0.052 0.054 0.057 0.060 0.062 0.065 0.067 0.070 0.073 0.075 0.078
5 85 .046 .048 .051 .054 .056 .059 .061 .064 .066 .069 .071 .074 .077
6 84 .046 .048 .051 .053 .056 .058 .061 .063 .066 .068 .071 .073 .076
7 83 .045 .048 .050 .053 .055 .058 .060 .063 .065 .068 .071 .073 .075
8 82 .045 .047 .050 .052 .055 .057 .060 .062 .065 .067 .070 .072 .075
9 81 .044 .047 .049 .052 .054 .057 .059 .062 .064 .067 .069 .071 .074
10 80 .044 .046 .049 .051 .054 .056 .058 .061 .063 .066 .068 .071 .073
11 79 .043 .046 .048 .050 .053 .055 .058 .060 .062 .065 .067 .070 .072
12 78 .043 .045 .047 .050 .052 .054 .057 .059 .062 .064 .066 .069 .071
13 77 .042 .044 .047 .049 .051 .054 .056 .058 .061 .063 .065 .068 .070
14 76 .041 .043 .046 .048 .050 .053 .055 .057 .059 .062 .064 .066 .069
15 75 .040 .043 .045 .047 .049 .052 .054 .056 .058 .061 .063 .065 .067
16 74 .040 .042 .044 .046 .048 .051 .053 .055 .057 .059 .061 .064 066
17 73 .039 .041 .043 .045 .047 .049 .052 .054 .056 .058 .060 .062 .064
18 72 .038 .040 .042 .044 .046 .048 .050 .052 .054 .057 .059 .061 .063
19 71 .037 .039 .041 .043 .045 .047 .049 .051 .053 .055 .057 .059 .061
20 70 .036 .038 .040 .042 .044 .046 .048 .050 .052 .054 .056 .058 .060
21 69 .035 .037 .038 .040 .042 .044 .046 .048 .050 .052 .054 .056 .058
22 68 .034 .035 .037 .039 .041 .043 .045 .047 .048 .050 .052 .054 .056
23 67 .032 .034 .036 .038 .040 .041 .043 .045 .047 .049 .050 .052 .054
24 66 .031 .033 .035 .036 .038 .040 .042 .043 .045 .047 .049 .050 .052
25 65 .030 .032 .033 .035 .037 .038 .040 .042 .043 .045 .047 .048 .050

26

 64 .029 .030 .032 .033 .035 .037 .038 .040 .041 .043 .045 .046 .048

27

 63 .027 .029 .030 .032 .033 .035 .037 .038 .040 .041 .043 .044 .046
28 62 .026 .028 .029 .030 .032 .033 .035 .036 .038 .039 .041 .042 .043
29 61 .025 .026 .027 .029 .030 .032 .033 .034 .036 .037 .038 .040 .041
30 60 .023 .025 .026 .027 .028 .030 .031 .032 .034 .035 .036 .038 .039
31 59 .022 .023 .024 .026 .027 .028 .029 .030 .032 .033 .034 .035 .036
32 58 .020 .022 .023 .024 .025 .026 .027 .028 .030 .031 .032 .033 .034
33 57 .019 .020 .021 .022 .023 .024 .025 .026 .027 .028 .029 .031 .032
34 56 .017 .018 .019 .020 .021 .022 .023 .024 .025 .026 .027 .028 .029
35 55 .016 .017 .018 .019 .019 .020 .021 .022 .023 .024 .025 .026 .027
36 54 .014 .015 .016 .017 .018 .018 .019 .020 .021 .022 .022 .023 .024
37 53 .013 .014 .014 .015 .016 .016 .017 .018 .019 .019 .020 .021 .021
38 52 .011 .012 .013 .013 .014 .014 .015 .016 .016 .017 .018 .018 .019
39 51 .010 .010 .011 .011 .012 .012 .013 .013 .014 .015 .015 .016 .016
40 50 .008 .009 .009 .009 .010 .010 .011 .011 .012 .012 .013 .013 .013
41 49 .006 .007 .007 .008 .008 .008 .009 .009 .009 .010 .010 .010 .011
42 48 .005 .005 .005 .006 .006 .006 .006 .007 .007 .007 .008 .008 .008
43 47 .003 .003 .004 .004 .004 .004 .004 .005 .005 .005 .005 .005 .005
44 46 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .003 .003 .003
45 45 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000


 Correction For Elevation In Inches Hg Per 100 Foot Difference In Elevation
To be added to barometer readings when above the datum plane or
subtracted from barometer readings when below the datum plane.
Altitude
feet		 Temperature, in degrees Fahrenheit
0 10 20 30 40 50 60 70 80 90
0 .122 .119 .117 .114 .112 .110 .108 .106 .104 .102
1000 .118 .115 .113 .110 .108 .106 .104 .102 .100 .098
2000 .113 .110 .108 .106 .104 .102 .100 .098 .096 .094
3000 .108 .106 .104 .102 .100 .098 .096 .094 .092 .090
4000 .104 .102 .100 .098 .096 .094 .092 .090 .088 .086
5000 .100 .098 .096 .094 .092 .090 .088 .086 .084 .082
6000 .096 .094 .092 .090 .088 .086 .084 .082 .081 .080
7000 .093 .091 .089 .087 .085 .084 .082 .080 .079 .078


Version 2.4.2
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