Expedition Navigation Software » Polar projection raster image import failed

Herman_NL · 2/13/2023 9:08 am

Hi,

I would like to import a polar projection with MSLP data from this source =13px http://www.bom.gov.au/fwo/IDY65100.pdf

After conversion into a picture I tried importing it into Exp as weather raster image. Geo-referenced top left (10n 40e) and bottom right (10n 140w) and marked the chart as "polar stereographic".

There is also half a polar projection with MSLP data available here =13px http://www.bom.gov.au/australia/charts/indian_ocean.shtml

Both return an error "unable to import".

Any suggestions are very welcome!

Herman

Ernie M · 2/13/2023 11:38 am

Herman
Being so large an area I'm not sure how well it will work but if you want to experiment;

Make sure you have the Lat Long correct for each point
use the format xx 0.0s xxx 0.0w with the lat first
use at least 3 points (maybe more will help)
I tried it and it worked but with some distortion, I used IDY65102 saved as a .png
let us know....
Cheers,
Ernie

Herman_NL · 2/13/2023 11:25 pm

Hi Ernie,

Thanks for the quick reply and tips. Mapping more raster points is the way forward for non-Mercator projections, that makes sense. Did importing with multiple Mercator projections and that worked excellent with only 2 raster points.

So I tried using the following 5 rasterpoints with a .png file format, but still an error returns. Could you please check what I did miss here? Or did you use other or more raster points?

Left Top= 10 00.000n 040 00.000e
Right Top= 10 00.000n 140 00.000e
South Pole= 90 00.000s 000 00.000e
Left Bottom= 10 00.000n 040 00.000w
Right Bottom= 10 00.000n 140 00.000w

Thanks in advance!

Last edited by Herman_NL (2/13/2023 11:28 pm)

Ernie M · 2/14/2023 8:06 am

Herman
I don't think 10n is the correct spot , check your geo spots
and I would avoid using 000 as a value
Ernie

Nick · 2/14/2023 10:57 am

I don't know if I have ever tried a hemispheric image. Will test today if I get time.

Where it is much use is another question - that is probably just an Access-G plot

Herman_NL · 2/14/2023 11:22 am

Ernie and Nick, thanks for your replies. I will try to import a smaller portion of the polar map. De facto this one, which is half of the first map I tried; http://www.bom.gov.au/australia/charts/indian_ocean.shtml

Also, I noted that cropping images back to much smaller areas help Exp when importing huge parts of the globe. An example is this synoptic map that I cropped back to 30 S 10 E and 50 S 80 E. That worked.

Last edited by Herman_NL (2/14/2023 11:24 am)

Nick · 2/14/2023 11:53 am

For sure, a polar stereographic projection is likely to have undefined transformations across the equator. You may be ok is all the reference points are in the southern hemisphere.

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» Polar projection raster image import failed

2/13/2023 9:08 am #1

Polar projection raster image import failed

2/13/2023 11:38 am #2

Re: Polar projection raster image import failed

2/13/2023 11:25 pm #3

Re: Polar projection raster image import failed

2/14/2023 8:06 am #4

Re: Polar projection raster image import failed

2/14/2023 10:57 am #5

Re: Polar projection raster image import failed

2/14/2023 11:22 am #6

Re: Polar projection raster image import failed

2/14/2023 11:53 am #7

Re: Polar projection raster image import failed

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