Hmm, the form it takes? Not sure I understand you. Let me try nevertheless.
A float8 is a single number. It's 64 bits of floating point, part of which is exponent and part of which is mantissa. The exponent is understood as a power of two. The most common double precision floating point representation in use today represents numbers to about 14 digits of accuracy in the range of 10^-308 to 10^308, negative and positive. There are other special numbers like ± infinity and NaN (not a number). Most computers use the IEEE 754-1985 standard for floating point. You can read all about this at http://en.wikipedia.org/wiki/IEEE_floating_point A concrete example of a float8 number is 1.4976931341623151×10^3 What you are looking at specifically - ST_Translate(geometry,float8,float8,float8) - takes a given geometry and "translates" (ie moves relative to the origin) by the three float8 offset values you provide. You might think of this as a shift. Let's say you called ST_Translate() on a point (x,y,z) with offset values (a,b,c). Then your translated coordinates would be: x' = x + a y' = y + b z' = z + c ST_Translate() is one of the three components of an affine transformation, the other two being ST_Scale() and ST_RotateZ(). Does this help? Bob Pawley wrote: > Any suggestions on the form it takes (integer, cooridinate, binary) > and how it is used with ST_Translate??? > > Bob > > ----- Original Message ----- From: "Chris Hermansen" > <[EMAIL PROTECTED]> > To: "PostGIS Users Discussion" <[email protected]> > Sent: Thursday, May 22, 2008 1:48 PM > Subject: Re: [postgis-users] Float 8 > > >> float8 is double precision, about 14 digits of precision to be precise >> :-) plus a bigger allowable exponent than float4 or single precision. >> >> Bob Pawley wrote: >>> Hi >>> >>> Would someone please tell me what is meant by float 8 in this >>> function? I know they refere to x, y and z coordinates. (An example >>> would help) >>> >>> ST_Translate(geometry, float8, float8, float8) >>> >>> Bob >>> _______________________________________________ >>> postgis-users mailing list >>> [email protected] >>> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> >> -- >> Regards, >> >> Chris Hermansen mailto:[EMAIL PROTECTED] >> tel+1.604.714.2878 · fax+1.604.733.0631 · mob+1.778.232.0644 >> Timberline Natural Resource Group · http://www.timberline.ca >> 401 · 958 West 8th Avenue · Vancouver BC · Canada · V5Z 1E5 >> >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://postgis.refractions.net/mailman/listinfo/postgis-users > > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users -- Regards, Chris Hermansen mailto:[EMAIL PROTECTED] tel+1.604.714.2878 · fax+1.604.733.0631 · mob+1.778.232.0644 Timberline Natural Resource Group · http://www.timberline.ca 401 · 958 West 8th Avenue · Vancouver BC · Canada · V5Z 1E5 _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
