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I have seabird tracking data from the South Pacific with several of the animals crossing the international date line during their travels. When I try to generate a polyline from the corresponding XY data, the resulting line is warped around the globe when two consecutive positions are on either side of the date line, i.e. rather than connecting the points along the shorted distance (which means crossing the date line), the tool draws the line across the entire map.

At first I though this was because the original data was in WGS1984 lat/lon data, so that latitudes range from -180 to +180 degrees, which explains the odd line drawing behaviour. However, converting the data to a projected format (e.g. Web Mercator) does not solve this issue.

Googling this issue shows that this has been an issue for a long time, but does not produce any satisfying solution. Any suggestions how to get something this basic done?

PolyGeo
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Tomm
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    You'll have to find a geographic coordinate system based on WGS84 that is Pacific Centered and project your coordinates into that, I found one that may work: EPSG:3832 (WGS84 PDC) is a Pacific Ocean centered projection. from https://gis.stackexchange.com/questions/7064/the-international-date-line-wrap-around - it's a fair way down the page so if it works for you please upvote the answer and let me know so I can upvote as well, to help a correct answer move closer to the top of the post. – Michael Stimson Mar 18 '24 at 01:31
  • Latitudes don't range from -180 to +180, longitudes do. But the problem with Web Mercator is the last few degrees latitude to the poles (which are infinitely far from the Equator). – Vince Mar 18 '24 at 01:56
  • Turns out not any Mercator projection will work. Web Mercator for example has the same issue as WGS84 as the projection still uses the central meridian as its base. Using the Pacific Centered projection as suggested by @MichaelStimson is key. If you add your comment as answer, I can accept it as solution, Michael. Thanks heaps. – Tomm Mar 18 '24 at 05:00
  • I'm glad that worked Tomm, what projection did you use? I won't answer this question as I believe the answer exists in the linked post already... I'd just be stealing their thunder. I encourage you to upvote the linked anwer so it pops up quicker when the next user searches for international date line projection problems. – Michael Stimson Mar 18 '24 at 05:59
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    Does this answer your question? The International Date Line wrap around – Son of a Beach Mar 19 '24 at 00:41

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While the comments to my original questions have put me on the correct path to solving this issue, I think it is worthwhile providing an answer related to ArcGIS Pro.

The crux of the problem is that most projections use Greenwich as central meridian which results in the warped line data. Therefore it is necessary to convert any point data to a projection that uses the Pacific meridian, i.e. the date line, before using the Data Management > Points to line tool.

It was suggested to use EPSG:3832 (WGS84 PDC); in my specific instance I used EPSG:2135 (NZGD 2000 UTM Zone 60). Both work.

Also, important to note that simply setting the map coordinate system in ArcGIS does not suffice. The point data itself need to be projected via Data Management > Project.

Tomm
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