latlon2geocode

  latlon2geocode(lat[, lon])

The latlon2geocode function encodes a given latitude/longitude coordinate into one long return value. This encoded value can be indexed and used with a special variant of Texis' BETWEEN operator for bounded-box searches of a geographical region.

The lat and lon parameters are doubles in the decimal degrees format (if you have ``degrees minutes seconds'' (DMS) format values, you can use dms2dec to convert them). Negative numbers represent south latitudes and west longitudes, ie. this function is east-positive (unlike Vortex <geo2code> which is west-positive).

Valid values for lat are -90 to 90 inclusive. Valid values for lon are -360 to 360 inclusive. A lon value less than -180 will have 360 added to it, and a lon value greater than 180 will have 360 subtracted from it. This allows longitude values to continue to increase or decrease when crossing the International Dateline, and thus avoid a non-linear ``step function''. Passing invalid lat or lon values will return -1. These changes were added in version 5.01.1193956000 20071101.

In version 5.01.1194667000 20071109 and later, the lon parameter is optional: both latitude and longitude (in that order) may be given in a single space- or comma-separated text value for lat. Also, a N/S suffix (for latitude) or E/W suffix (for longitude) may be given; S or W will negate the value.

EXAMPLE

  create table geotest(city varchar(64), lat double, lon double,
                       geocode long);
  insert into geotest values('Cleveland', 41.4, -81.5,
                             latlon2geocode(41.4, -81.5));

For more examples of using latlon2geocode, see the geocode script in the texis/samples directory.

CAVEATS

The geocode value returned by latlon2geocode is platform-dependent in format and accuracy; it should not be copied across platforms. On platforms with 32-bit longs it is accurate to about 32 seconds (around half a mile, depending on latitude). -1 is returned for invalid input values (in version 5.01.1193955804 20071101 and later).

NOTES

The geocodes produced by these functions are compatible with the codes used by the Vortex functions <code2geo> and <geo2code>. However, the <code2geo> and <geo2code> functions take DMS format (as described in the dec2dms and dms2dec SQL functions).