Día Juliano en PostgreSQL

CREATE OR REPLACE FUNCTION to_julian(f date)
    RETURNS integer AS
$BODY$
BEGIN
    RETURN cast(to_char(f, 'J') as integer);
END;
$BODY$
LANGUAGE 'plpgsql'

Cambiar Sistema de Referencia con gdalwarp

GDALWARP es una práctica herramienta para cambiar fácilmente de un sistema de referencia a otro.

Usage: gdalwarp [--help-general] [--formats]
[-s_srs srs_def] [-t_srs srs_def] [-to "NAME=VALUE"]
[-order n] [-tps] [-rpc] [-geoloc] [-et err_threshold]
[-te xmin ymin xmax ymax] [-tr xres yres] [-ts width height]
[-wo "NAME=VALUE"] [-ot Byte/Int16/...] [-wt Byte/Int16]
[-srcnodata "value [value...]"] [-dstnodata "value [value...]"] -dstalpha
[-r resampling_method] [-wm memory_in_mb] [-multi] [-q]
[-cutline datasource] [-cl layer] [-cwhere expression]
[-csql statement] [-cblend dist_in_pixels]
[-of format] [-co "NAME=VALUE"]*
srcfile* dstfile

Ejemplo:

#$ gdalwarp -s_srs EPSG:4326 -t_srs EPSG:900913 input_img.tif output_img.tif

Donde:
-s_srs EPSG:4326 el sistema de referencia de origen
-t_srs EPSG:900913 el sistema de referencia de destino