The Algorithm
From Geohashing
Revision as of 15:39, 13 June 2008 by imported>Tjtrumpet2323 (→Calculational Aids)
This time, we did invent the algorithm!
- Strings of the current date (in yyyy-mm-dd format) and the daily opening price of the Dow Jones Industrial Average (as quoted at finance.google.com) are concatenated, with a hyphen separating the two.
- West of -30° longitude: If there is no opening price for the Dow on the desired day, the opening price from its previous day of active trading is used instead.
- East of -30° longitude: Same as west, except the Dow's opening price for the previous day is used, even if a new one becomes available later in the day in your time zone. That is, Thursday uses Wednesday's open, Friday uses Thursday's open, and Saturday through Monday all use Friday's open. (see 30W Time Zone Rule)
- The resulting string is then fed through the well-documented MD5 cryptographic algorithm to generate as pseudo-random (yet easily verifiable) "hash" of 32 hexadecimal digits.
- The "hash" is then split into two halves of 16 hexadecimal digits each.
- Each half of the "hash" is prepended with a decimal point (so as to represent a hexadecimal fraction) and is converted to a base-10 fraction.
- The resulting decimal fractions are appended to the integral (lat,lon) values of any given graticule to produce that graticule's geohash target for the day.
Calculational Aids
- Online md5() generator
- Fractional hexadecimal-to-decimal calculation
- Dow source
- For those wishing to capture the opening price directly from finance.google.com, the tag containing the opening data is: <span id="ref_983582_op">99,999.99</span>
- Other sources are available at Dow Jones Industrial Average.
