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).