Weatherfax and Sea Surface Temps

[Chessyman]

I have been trying to use the weatherfax plugin to open Rutgers Sea Surface Temps. I can open the converted jpeg file, but don’t understand how to calibrate it and get it to overlay a chart. I have calibrated converted files of charts in SeaClear using MapCal. Do I need to convert the jpeg file, calibrate in MapCal and convert it back to maybe BSB?

When I experiment with the jpeg file in weatherfax it looks like there is a way to calibrate it, but I have not been successful.

Thank for any help

[sailorF54]

They are plain mercator chartlets (with easy to use lat / long marks)
Open the .jpg file in the plugin, next to the calib page. Select Mercator if not default, Click on the uppermost leftmost round number coordinate (red lines) enter values (here 46 N 71 W (W is minus), same for lowermost rightmost (green lines) hit 'Get Aspect Ratio', then next (back to O)
Adjust transparency to taste

You can use the whole chartlet, or crop it beforehand.

[rgleason]

Read the wxfax instructions. There is a wizard that you use to set the opp corners.

[Chessyman]

I have tried this several times now and it hasn't workded. The first time it did work the overlay was hundreds of miles off. After a few more tries I got thin strip streaching across the base map. Then the next time I got and over zoom on the chart and while trying various ways to zoom down OpenCPN crashed.

The crash occured on a cropped jpeg that I was trying to overlay on a large scale chart. Larger than the scale of the overlay.

I am guessing I have to overlay the calibrated jpeg on a chart of smaller scale than the overlay.

I didn't try the Wizard it looks to me like it is for data that contains GIS information and wouldn't work with jpeg files.

What do you think?

[rgleason]

The crash occured on a cropped jpeg that I was trying to overlay on a large scale chart. Larger than the scale of the overlay.

I am guessing I have to overlay the calibrated jpeg on a chart of smaller scale than the overlay.

I didn't try the Wizard it looks to me like it is for data that contains GIS information and wouldn't work with jpeg files.

What do you think?

Chessyman.

I am sorry it crashed. If this keeps occurring there may be something that has changed with the plugin, and I will have to test it again.

Wx Faxes and Weather charts are usually image files, which can be easily handled by WeatherFax_pi. It handles all the normal file types, gif, jpeg, png etc.

You MUST use the Wizard to set the diagonal coordinate points, by looking at the Lat Long for two diagonal points at the corners, then set those data points in the Wizard, and select the exact points with the cursor. It will take some time to get used to it.

I suggest that you go ahead and try to use the wizard. I don't think you have read the documentation, sparse as it may be, it does show how to do it. I wrote it a long time ago.

Good luck.