Re: [ferret_users] ppl commands for a Vector overlay on a projection.

[Ansley Manke <a.c.manke@xxxxxxxxx>]

Hi Alexander,

I haven't tried your examples in any detail, but I think for the map 
projection vector overlay to work correctly, you would need to have the 
vector variables on the same grid as the underlying plot.  That way the 
x_page, y_page coordinate variables are defined once and are consistent 
for the plot:

USE RawERA5WindSpeed500Annual.nc
USE RawERA5WindSpeedComp500annual.nc
go mp_mcbryde_fpq
go mp_grid p[D=1]

Set window/asp=0.7 1
SHADE/PALETTE=difference/nolab/LEVELS=(-38, 38, 2) p[D=1], x_page, y_page

let uwnd_ov = uwnd[d=2,gxy=p[d=1]]
let vwnd_ov = vwnd[d=2,gxy=p[d=1]]

VECTOR/overlay/Thickness=0.25/Xskip=60/Yskip=40/set Uwind_ov, Vwind_ov, 
x_page, y_page
ppl VECSET 0.25,25
ppl VECKEY/NOUSER 3.5,1,,(f3.0," m/s")
ppl vector/overlay




On 6/21/2021 9:05 AM, Alexander Audet wrote:
> Hello ferret community,
>
>                     Not sure if this is an impossible combination, but 
> I was trying to see if I could refine my vector overlay over my 
> projected shade. In one method, I try to use PPlus commands after 
> setting up the vector overlay, however, without fail this creates a 
> black map and does not seem to produce the desired effect with the legend.
>
> USE RawERA5WindSpeed500Annual.nc
> USE RawERA5WindSpeedComp500annual.nc
> go mp_mcbryde_fpq
> go mp_grid p[D=1]
> go mp_grid Vwind, Uwind
> Set window/asp=0.7 1
> SHADE/PALETTE=difference/nolab/LEVELS=(-38, 38, 2) p[D=1], x_page, y_page
> VECTOR/overlay/Thickness=0.25/Xskip=60/Yskip=40/set Uwind, Vwind, 
> x_page, y_page
> ppl VECSET 0.25,25
> ppl VECKEY/NOUSER 3.5,1,,(f3.0," m/s")
> ppl vector/overlay
> GO mp_land
> go mp_label 675,80,0,0,0.13  "ERA5"
> PPL COLOR,6,50,50,50
> Go mp_graticule 0, 360, 20, -90, 90, 20, 6, 1
>
> In another variation, I can use PPlus commands before shading, 
> however, while this does impact the standard vector length, and the 
> format of the vactor key, it does not place the key where desired. It 
> even seems to have mixed results about getting the scale correct, and 
> I think when it gets it correct, it might just be due to rounding.
>
> USE RawERA5WindSpeed500Annual.nc
> USE RawERA5WindSpeedComp500annual.nc
> go mp_mcbryde_fpq
> go mp_grid p[D=1]
> go mp_grid Vwind, Uwind
> Set window/asp=0.7 1
> SHADE/PALETTE=difference/nolab/LEVELS=(-38, 38, 2)/set p[D=1], x_page, 
> y_page
> ppl VECSET 0.25,25
> ppl VECKEY 1,1,,(f3.0," m/s")
> ppl shade
> VECTOR/over/NOLABELS/KEY/Thickness=0.25/Xskip=60/Yskip=40 Uwind, 
> Vwind, x_page, y_page
> GO mp_land
> go mp_label 520,80,0,0,0.13  "ERA5"
> PPL COLOR,6,50,50,50
> Go mp_graticule 0, 360, 20, -90, 90, 20, 6, 1
>
> I can live without the scale placement as I can always move it in 
> illustrator, though it may be a pain to keep it the correct size when 
> resizing my images, however not being able to control the scale could 
> be a dealbreaker.
>
> Cheers!
>
> Alexander