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Creating maps when crossing the dateline

abmayfield

Contributor

Joined:

Jun 18, 2018

I have a very unusual issue that is surely NOT to be very widely applicable: I am working with samples obtained very close to the international dateline (Fiji). When I go to overlay the data onto a map using pre-created shape files (one feature I love about JMP, BTW), it basically plots them on opposite sides of the globe, rather than center them around the 180 degree dateline. Upon a quick Googling, I noticed that this is an issue in other graphing software. I tried changing the access to geodesic, but this did not help. I tried to make a plot and place a background map of FIji behind it to see if this would do the trick, but it basically would not load the map! Any thoughts?

Anderson B. Mayfield
1 ACCEPTED SOLUTION

Accepted Solutions
Craige_Hales

Staff

Joined:

Mar 21, 2013

Solution

Add 360 to the negative longitude.

Capture4.PNGformula to add 360the image maps wrap but the outlines do not.

Capture5.PNGoutline does not wrap

Craige
10 REPLIES
Craige_Hales

Staff

Joined:

Mar 21, 2013

Solution

Add 360 to the negative longitude.

Capture4.PNGformula to add 360the image maps wrap but the outlines do not.

Capture5.PNGoutline does not wrap

Craige
abmayfield

Contributor

Joined:

Jun 18, 2018

Great! This seems to do the trick. I'll just need to manually change the y-axis (i.e., longitude) when I go to make the actual figure (i.e., convert 181 degrees back to -179). Thanks. 

Anderson B. Mayfield
Jeff_Perkinson

Community Manager

Joined:

Jun 23, 2011

Actually, I'm curious about the problem that you're seeing as it works for me if I've got the Geodesic axis scale on both X and Y.

 

Try the attached data table and the script in it and see what you get.

 

Here's my result.

Parallels DesktopScreenSnapz059.png

 

-Jeff
abmayfield

Contributor

Joined:

Jun 18, 2018

Jeff, 

Your data table plots correctly, but for some reason mine does not. Maybe I input something wrong? If you plot latitude versus longitude using in this table, they are plotted on opposite sides of the globe, even when set to geodesic!

Anderson B. Mayfield
Jeff_Perkinson

Community Manager

Joined:

Jun 23, 2011

Sorry, I forgot to mention that you need to adjust the longitude (x) axis so that -180 is in the middle.

Jul-13-2018 16-44-07.gif

-Jeff
abmayfield

Contributor

Joined:

Jun 18, 2018

Now something is really going on with my graph: the longitude doesn't "wrap" at 180 but keeps going and going. Therefore, centering it at -180 degrees still gives a non-real presentation. It seems like changing the setting to "geodesic" should fix this?

 

Screen Shot 2018-07-13 at 16.58.52.png

Anderson B. Mayfield
Jeff_Perkinson

Community Manager

Joined:

Jun 23, 2011

That's what you get if you only set the Longitude (X) axis to Geodesic. 

 

You need to set Latitude (Y) to Geodesic also.

-Jeff
abmayfield

Contributor

Joined:

Jun 18, 2018

If I set both to axes geodesic, I get the attached image. I also tried geodesic US, but the outcome was the same. In any event, it's not hard to add 360 to the negative values, so I think I can just do that. 

Screen Shot 2018-07-13 at 17.12.41.png

Anderson B. Mayfield
Jeff_Perkinson

Community Manager

Joined:

Jun 23, 2011

Yes, that's correct. Notice that the Latitude axis is going from -163 to 125. Adjust it to zoom in to the range of your actual data. I add a background map below just to make it clearer whats going on.

 

Jul-13-2018 17-24-06.gif

-Jeff