![\"\"](\"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.2.8_fig_1_rev.jpg\")
Hour angle.<\/p><\/div>\n
ON is the observer\u2019s meridian while XN is the meridian passing through the body.\u00a0 Angle ONX is the hour angle<\/p>\n
Greenwich Hour Angle (GHA).<\/strong> Local Hour Angle (LHA).<\/strong> Local hour angle (LHA).<\/p><\/div>\n GN is the meridian passing through Greenwich, ON is the observer\u2019s meridian (to the west of Greenwich), O2N is the observer\u2019s meridian (to the east of Greenwich)\u00a0\u00a0 \u00a0and XN is the meridian passing through the body.\u00a0 Angle GNX is the GHA, angle GNO is the observer\u2019s longitude and angles \u00a0ONXand O2NX are the LHA\u2019s.<\/p>\n (a) In the case of the observer being to the west of Greenwich (at O):<\/strong> (b) In the case of the observer being to the east of Greenwich (at O2):<\/strong> The positions of the meridians relative to one another can cause confusion so as a standing rule, the following is to be adhered to in the circumstances indicated: Since the declination gives us the \u201clatitude\u201d of the heavenly body we must now find it\u2019s \u201clongitude\u201d. We do this by measuring the angle between the celestial meridian passing through the body and that running through the observer\u2019s position. The hour angle is defined as \u201cthe angle between the meridian […]<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4,9,17],"tags":[],"class_list":["post-203","post","type-post","status-publish","format-standard","hentry","category-11-1-navigation","category-11-1-2-astro-navigation","category-11-1-2-3-hour-angle"],"_links":{"self":[{"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/posts\/203"}],"collection":[{"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/comments?post=203"}],"version-history":[{"count":8,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/posts\/203\/revisions"}],"predecessor-version":[{"id":310,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/posts\/203\/revisions\/310"}],"wp:attachment":[{"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/media?parent=203"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/categories?post=203"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-json\/wp\/v2\/tags?post=203"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\nWhen the observer is on the Greenwich meridian, the hour angle of a heavenly body is known as the GHA.\u00a0 The GHA is tabulated for every hour of GMT in the nautical almanac.\u00a0 For the value between these times, the interpolation tables at the back of the almanac must be used.\u00a0 \u00a0If you substitute \u201cG\u2019\u201d for \u201cO\u201d in the above sketch then angle GNX is the GHA.<\/p>\n
\nThe hour angle measured from the observer\u2019s meridian is known as the LHA and can be obtained by\u00a0 looking up the GHA for the particular time (remember that the GHA is tabulated in GMT and that if LMT is used or stated, it must first be converted to GMT)<\/strong> and by applying the longitude to produce the LHA.<\/p>\n![\"\"](\"https:\/\/maritimesa.org\/nautical-science-grade-11\/wp-content\/uploads\/sites\/6\/2020\/10\/11.1.2.8_fig_2.jpg\")
\nGHA = GNX (measured clockwise)
\nLong = GNO (measured clockwise)
\nLHA = [ONX (measured clockwise)]
\n= GNX – GNO
\n= GHA – long
\n(If [GHA \u2013 long] results in a negative value then 360\u00b0 must be added to the result).<\/p>\n
\nGHA = GNX (measured clockwise)
\nLong = GNO2(measuredanti-clockwise)
\nLHA = O2NX (measured clockwise)
\n= GNX +\u00a0 GNO
\n= GHA + long
\n(If the sum is greater than 360, then 360\u00b0 must be deducted from the result).<\/p>\n
\n(a)\u00a0When the longitude is west<\/strong>, you will always subtract it from the GHA<\/strong>.\u00a0 If you end up with a negative result, add 360\u00b0.
\n(b)\u00a0When the longitude is east<\/strong>, you will always add it to the GHA<\/strong>.\u00a0 If the result is greater than 360\u00b0, subtract 360\u00b0.<\/p>\n","protected":false},"excerpt":{"rendered":"