For references, see http://jclahr.com/science/software/hypo71/ web page.

This is a slightly modified of Hypo71PC, USGS location program used in several observatories since more than 30 years.
Those modifications have been introduced by Alexandre Nercessian (IPGP - France) and are used successfully on French volcanoes for many years.

Modifications includes :
	- up to 250 stations are possibles in the station cards;
	- stations altitudes are taken into account for the location process;
	- earthquakes above stations are possible;
	- stations below sea level are possible.

Added Test values from original Hypo71PC :
	- TEST(15) is the maximum altitude to expect earthquake in km (negative number);
	- TEST(20) is the coefficient by which Hypo71PC multiply altitude readings to obtain then in m.

RESET TEST(15)=-2	-> no earthquakes are expected above 2km above sea level.
RESET TEST(20)=1	-> altitude readings are in meters.
RESET TEST(20)=10	-> altitude readings are in 10'th of meters. This allow to have sea bottom station (altitude of -245 is a seismometer at 2450m below sea level).


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2017.11 : new modifications to ensure a safe crossing of the Greenwich Meridian (lon = 0°)
          (bug present in the original version of Hypo71, revealed in the Pyrenees where
          the pathological case "lon(closest station) x lon(epicenter) < 0 is not uncommon)
          M. Sylvander (Toulouse, France)
