David and All,

the lcc is a map projection that goes from Polar Stereographic
(used by UKMO, "Bracknell" chart) down to Standard Mercator.
It is a standard projection e.g. used in aviation maps. The very
non standard way is how DWD has choosen their parameter set.
DWD uses lcc close to the above Stereographic. If users accept
certain offsets in coastlines and grid you can try to find a set of
parameters using the UKMO projection but you probably won't
get happy with that. The DWD overlays will be of more interest
with MTG data as they are rather high resolution and there is
also a 3 hourly version with good coverage of western Europe.

You certainly remember winter storm "BARRA". Here is a number
of satpy images with UKMO, OPC and DWD overlays of this event.

https://we.tl/t-dRduJafzgR

wetransfer link, BARRA.zip 178MB (link valid one week from now)


Cheers,
Ernst

On 28/08/2022 14:44, Ernst Lobsiger via groups.io wrote:

   Unless GSS knows lcc already this will ask for some hours of coding.

Yes, it's an unusual and, dare I say it, non-standard projection. Instead GeoSatSignal already has the option of using:

https://www.weathercharts.net/ukmo_mslp_analysis/ppva.gif

so that is the solution I suggest. Thanks for the hint on the projection.

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv

On 28/08/2022 14:44, Ernst Lobsiger via groups.io wrote:

@David, if you *really* want to go this lcc route I attach an example overlay
that I use with my SatPy scripts. To prevent you from reinventing the wheel
I also have CMD scripts to download and prepare DWD overlays from the web.
And last but not least you must know the lcc parameters and area definitions.
I found those out the hard way (Levenberg-Marquardt) as DWD was of no help.

Ernst,

I should mention that GeoSatSignal users already have an automated program for downland charts (and other data) from Francis Breame called getCharts. It's available here:

http://www.elnath.org.uk/

If the data is LCC I will likely suggest one of the existing sources providing the same overlay data.

Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv

On 28/08/2022 14:44, Ernst Lobsiger via groups.io wrote:

@David, if you *really* want to go this lcc route I attach an example overlay
that I use with my SatPy scripts. To prevent you from reinventing the wheel
I also have CMD scripts to download and prepare DWD overlays from the web.
And last but not least you must know the lcc parameters and area definitions.
I found those out the hard way (Levenberg-Marquardt) as DWD was of no help.

Best regards,
Ernst

Ernst (and GeoSatSignal users),

The program accepts overlay files from many different sources. As I already
replied to the OP, I have been busy this weekend, but will address the issue on
Monday, all being well. I adapt the program to use the projections in which
the overlay is prepared, as I have done for many different sources.

Cheers,
David
--
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-taylor@...
Twitter: @gm8arv

Dear All,

there is a question about using the Deutscher Wetter Dienst (DWD)
synoptic overlays (MSLP charts) with GeoSatSignal in this thread:

https://groups.io/g/SatSignal/topic/93235941#23299

I have none of David's software and no subscription of it's groups list.
That's why I'm answering on MSG-1. I cannot know what GSS is capable
of, but I *doubt* DWD overlays can easily be used for these reasons:

1) AFAIK I pioneered the use of Ocean Prediction Center (OPC) and DWD
    overlays one year ago. In both cases I know what I'm talking about.

2) I asked DWD *twice* for the map projections used. They had no clue.

3) IMHO it's not a good idea to use the proposed gifs from
 
   https://www1.wetter3.de/fax_dt.html

   that are scaled down (and distorted) versions of the originals.

4) The originals are found on the WEB (a subset is on E1B-DWDSAT):

   https://opendata.dwd.de/weather/charts/

./analysis/Z__C_EDZW_20220826142031_tka01,ana_bwkman_dwdc_O_000000_000000_202208261200_WV12.png
./analysis/Z__C_EDZW_20220826142035_tka01,ana_bwkman_dwdna_O_000000_000000_202208261200_WV12SW.png
./analysis/Z__C_EDZW_20220826153244_nwv01,ico_p00_na_N_000000_999999_202208261200_WV11.png
./analysis/Z__C_EDZW_20220826155026_tka01,ana_bwkman_dwda_O_000000_000000_202208261500_WV12SW.png

There are coloured versions *WV12.png and monochrome versions *WV12SW.png (SW = Schwarz Weiss).
Channel E1B-DWDSAT has only some SW versions and if you don't have it already you must register with DWD.

To automate download from link  https://opendata.dwd.de  DWD offers a Python script (since I told
them that the original bash script was buggy and resulted in multiple downloads of the same files).

5) Appart from dwdc, that is an easy to recognize stereographic (stere),
    DWD uses a special Lambert Conformal Conic (lcc) with two parallels.

   https://en.wikipedia.org/wiki/Lambert_conformal_conic_projection

   https://proj.org/operations/projections/lcc.html

   Unless GSS knows lcc already this will ask for some hours of coding.

@David, if you *really* want to go this lcc route I attach an example overlay
that I use with my SatPy scripts. To prevent you from reinventing the wheel
I also have CMD scripts to download and prepare DWD overlays from the web.
And last but not least you must know the lcc parameters and area definitions.
I found those out the hard way (Levenberg-Marquardt) as DWD was of no help.

Best regards,
Ernst