Re: [ferret_users] Create an image to be georeferenced

[mick spillane <mick.spillane@xxxxxxxx>]

Hello All,
   A method I've used in making images to overlay on Google Earth is to 
create borders that extend a known distance in lat/lon units beyond the 
axes. The script "chartborder.jnl" given below does this. The variable 
"maxlen" is something I use in a related situation.  Often I want to get 
the aspect ratio of the axes right but don't know in advance whether the 
x or y-axis should be longer.  So I would use "go chartaxes 12 ..." to 
set up a plot with the longer axis 12 inches long and the other whatever 
it neeads to be to get the aspect ratio right.

Hope these may be of use to someone else.
Mick
PS Another useful feature of the "chartborder" approach (I think) is 
that a colorbar outside the axes can appear next to the georeferenced 
image in Google Earth.


------------------------
! chartborder : assigns chart axes lengths given a desired longer
!             axis length and the lowerleft and upperright coords
! *** adapted from chartaxes.jnl, this version attempts to create ***
! *** a border of known width around the image to facilitate use  ***
! ***              with Google Earth                              ***

! usage: chartborder maxlen lon1 lat1 lon2 lat2 xborder yborder
!        where (lon1,lat1), (lon2,lat2) are the lower left and
!                                       upper right corners
!              maxlen is the major axis length, and
!              xborder,yborder are the desired border widths

let d2r=atan(1.)/45
let maxlen=$1
let xdegrees=($4-$2)*cos(d2r*($5+$3)/2)
let ydegrees=$5-$3
let axratio=ydegrees/xdegrees
let xaxlen=if(axratio le 1)then $1 else $1/axratio
let yaxlen=if(axratio le 1)then $1*axratio else $1
ppl axlen,`xaxlen`,`yaxlen`

let xborderwid=$6*xaxlen/xdegrees ; let yborderwid=$7*yaxlen/ydegrees
; ppl size,`xaxlen+2*xborderwid`,`yaxlen+2*yborderwid`
ppl origin,`xborderwid`,`yborderwid`

----------------------------------
! chartborder : assigns chart axes lengths given a desired longer
!             axis length and the lowerleft and upperright coords
! *** adapted from chartaxes.jnl, this version attempts to create ***
! *** a border of known width around the image to facilitate use  ***
! ***              with Google Earth                              ***

! usage: chartborder maxlen lon1 lat1 lon2 lat2 xborder yborder
!        where (lon1,lat1), (lon2,lat2) are the lower left and
!                                       upper right corners
!              maxlen is the major axis length, and
!              xborder,yborder are the desired border widths

let d2r=atan(1.)/45
let maxlen=$1
let xdegrees=($4-$2)*cos(d2r*($5+$3)/2)
let ydegrees=$5-$3
let axratio=ydegrees/xdegrees
let xaxlen=if(axratio le 1)then $1 else $1/axratio
let yaxlen=if(axratio le 1)then $1*axratio else $1
ppl axlen,`xaxlen`,`yaxlen`

let xborderwid=$6*xaxlen/xdegrees ; let yborderwid=$7*yaxlen/ydegrees
; ppl size,`xaxlen+2*xborderwid`,`yaxlen+2*yborderwid`
ppl origin,`xborderwid`,`yborderwid`
facts> more chartaxes.jnl
! chartaxes : assigns chart axes lengths given a desired longer
!             axis length and the lowerleft and upperright coords

let d2r=atan(1.)/45
let maxlen=$1
let xdegrees=($4-$2)*cos(d2r*($5+$3)/2)
let ydegrees=$5-$3
let axratio=ydegrees/xdegrees
let xaxlen=if(axratio le 1)then $1 else $1/axratio
let yaxlen=if(axratio le 1)then $1*axratio else $1
ppl axlen,`xaxlen`,`yaxlen` ; ppl size,`xaxlen+1.5`,`yaxlen+1.5`
ppl origin,0.75,0.75


Jaison Kurian wrote:
> Hi Tony,
>            I think it is possible...two/three ways ...
>
>  1. before making plot, set all margins to zero
>
>          yes? go margins 0,0,0,0
>
>  2. use "/AXES" qualifier to define a viewport without margins
>
>          yes? define view/AXES/xlim=0:1/ylim=0:1 v1 ; set view v1
>
>
>  3. The problem with methods 1 and 2 is that, a very small white band
>         will appear on the top side. I don't know how to get rid of
>         this. Anyway you can try the following options (and is valid
>         for a plot made in normal way with /nolab/nokey/noaxes 
> qualifiers)
>
>         3.1 Use some tools like gimp/xv to chop off the white band.
>
>         3.2 Lengthy solution.....make a ps file, corrent the bounding
>              box (open the ps file in text editing tool and adjust the
>              arguments for "%%BoundingBox" in the 5th line)...convert
>              it to gif using linux command "convert".
>
> Regards,
>
> Jaison
>
> On Wed, 21 Jun 2006, Tony Jolibois wrote:
>
> >        Hi all,
> >
> > Is it possible with ferret to create an image without any label, key or
> > axis, just the field, in order to be able to georeference it (see images
> > attached, first with labels, second can be georeferenced).
> > When I try the fill command with /nolabs/nokey/noaxis, there is a white
> > band around the image, so it can not be georeferenced, must cut the band
> > before.
> >
> > Thanks in advance,
> > Tony