It's well known why we launch satellites near the equator, but why are the GPS control/monitor segments located near the equator at Hawaii, Ecuador, Florida, Bahrain, Ascension, Diego Garcia, Guam and Kwajalein?
For example:
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2Which locations and/or precise legend items from your map are you considering to be "near the equator'? – PolyGeo♦ Sep 4 '16 at 20:31
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Hawaii, Ecuador, Florida, Bahrain, Ascension, Diego Garcia, Guam, Kwajalein – michael Sep 5 '16 at 5:11
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1Ground antennas on the equator are more likely to have a good angle to the satellites as they vary from ~55N to ~55S ground track. – BradHards Sep 5 '16 at 5:41
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They don't seem to be 'near the equator'. Roughly georeferencing the locations of the stations and looking at the distribution of latitudes:
Data (very rough, but OK for these purposes):
wkt_geom name lon lat
Point (-152.0 61.0) Alaska -152.0 61.0
Point (-61.6 76.4) Greenland -61.6 76.4
Point (-156.5 20.7) Hawaii -156.5 20.7
Point (-121.3 35.9) Vandenburg -121.3 35.9
Point (-103.3 37.3) Colorado -103.3 37.3
Point (-76.1 40.3) New Hampshire -76.1 40.3
Point (-76.5 37.4) Washington -76.5 37.4
Point (-80.5 27.9) Cape Canaveral -80.5 27.9
Point (-78.1 1.4) Ecuador -78.1 1.4
Point (-57.2 -34.8) Argentina -57.2 -34.8
Point (-1.2 52.7) UK -1.2 52.7
Point (50.3 25.0) Bahrain 50.3 25.0
Point (-10.4 -11.0) Ascension -10.4 -11.0
Point (26.9 -27.9) South Africa 26.9 -27.9
Point (127.7 35.4) South Korea 127.7 35.4
Point (72.0 -7.2) Diego Garcia 72.0 -7.2
Point (144.9 13.2) Guam 144.9 13.2
Point (138.3 -33.9) Australia 138.3 -33.9
Point (172.9 -41.3) New Zealand 172.9 -41.3
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1I'd plot monitoring stations distinctly from ground antenna locations. Different functions, different geometry. – BradHards Sep 5 '16 at 6:36
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I assume that you're asking about the ground stations at Ascension, Diego Garcia and Kwajalein. The reason is pretty simple: they already housed US Air Force bases and complexes, as well as space launch tracking and ground infrastructure, and as the NAVSTAR system is operated by the AFSPC, it's only logical to place the ground stations in a place controlled and maintained by the US Air Force.
I don't think there is any technical demands to place these station as close to the equator as possible, it's rather a matter of money and military control.
