1 2 Previous Next 24 Replies Latest reply on Dec 17, 2015 9:41 AM by allan.walker.0

    Mapping arctic coordinates?

    James Foote

      In Tableau 8.0 is there a way to map arctic coordinates?

       

      I have some arctic ice data I'd like to visualize, but I haven't found a way to use a polar region map in Tableau.  As I understand it we can import a map into Tableau via WMS, but only if that map is using the EPSG:4326 projection (see http://community.tableau.com/thread/109964 and http://community.tableau.com/ideas/1448).  Evidently EPSG:4326 is shorthand for Plate Carree projection which isn't going to work for polar regions.

       

      The National Snow & Ice Data Center (NSIDC) provides many polar map projections including EPSG:3575 at their web site but I don't see any obvious way to use them with Tableau.

       

      Allan Walker's Crowd Sourced WMS Server post suggested using Geoserver to draw projections other than EPSG:4326 onto the Tableau canvas.  Would this strategy work for polar maps also?  And if so, can anybody point me to a tutorial or at least an outline of the technique?

       

      Or maybe it would be possible to fool Tableau into treating projected azimuthal coordinates as spherical mercator similar to this trick for TileMill?


      I can imagine a coordinate transformation that creates a new map with a pseudo equator along the prime meridian then projecting that with EPSG:4326 and export that from a local WMS server.  Then run the same transformation on my lat/lon points and import the modified location data to Tableau. But ouch. Surely somebody's already tackled this in a more elegant way!

       

      Thanks,

       

      -Jim

        • 1. Re: Mapping arctic coordinates?
          James Foote

          Hi Shawn,

           

          The data I'm using is from this set:

          Submarine Upward Looking Sonar Ice Draft

           

          These are sanitized data tracks from submarines cruising under the ice cap and measuring ice thickness from underneath.  Ultimately I'd like to generate an interactive viz that looks something like this:

          Submarine Tracks

           

          In order to do that I'm going to have to write some scripts to extract the track data from the text files.  No problem, I can do that, but I don't want to invest too much time on that if I'm not ultimately going to be able to plot the tracks on a map in Tableau.

           

          As a test I first extracted a couple of points:

           

          Beginning LatitudeBeginning LongitudeEnding LatitudeEnding Longitude
          84.66.284.56.7

           

          If you use the default Tableau map you'll see it attempt to plot the points at the far end of a very distorted Mercator projection.  That's the expected result since the default maps are (I think) EPSG:4326 Plate Carree projections. 

           

          If I could figure out a way to plot these points on a map that Tableau understood (with the north pole near the center) I'd go head and spend the time to extract the rest of the data.  I think you're comment nails it:

           

          > The tricky part will be getting the data and image registered properly.

           

          My fear is that Tableau is locked in on Mercator x-y-ish grids for plotting.  That's a perfectly reasonable design tradeoff as the Arctic Submarine Ice Thickness Visualization market is small!   I'm just checking for hints in case someone else has tried something like this.

           

          It's true that I don't actually need the adjacent land boundaries - a map would be easier to understand but an open ocean plot would work.  But even in that case I'm not sure how to get Tableau to accurately represent the tracks.

           

          Thanks!

           

          -- Jim

          • 2. Re: Mapping arctic coordinates?
            James Foote

            It looks like the four corners are all at 65 N:

             

            65N 45W

            65N 135W

            65N 135E

            65N 45E

             

            Thanks!

             

            -- Jim

            • 3. Re: Mapping arctic coordinates?
              James Foote

              For reference, I asked the same question about reprojection at the GIS StackExchange forum - here's a link.

               

              There may be enough clues in the answers there to do the reprojection I think I need.

               

              -- Jim

              • 4. Re: Re: Mapping arctic coordinates?
                James Foote

                Thanks Shawn!

                 

                Here's a spreadsheet with the transit leg beginning and ending lat/lons for the 1975 cruise, let me know if it isn't what you're looking for.

                 

                -- Jim

                • 5. Re: Re: Mapping arctic coordinates?
                  James Foote

                  Thanks Shawn!

                   

                  Well, yes, I do have a bunch of questions!

                   

                  First, is there a way for me to view your Arctic Map Project.twbx from Tableau Public?  My understanding was that Tableau Public could only view workbooks uploaded to the tableau public server - if so, any chance of getting you to publish it there so I can view it? 

                   

                  Second, can you give me an overview of the recipe you used?  I'll need to do the same thing eventually so I'd like to be able to reproduce your steps.

                   

                  Thanks!

                  • 6. Re: Re: Mapping arctic coordinates?
                    James Foote

                    Hi Shawn,

                     

                    Yes, that's what I'm looking for.  Thanks!

                     

                    -- Jim

                    • 7. Re: Re: Mapping arctic coordinates?
                      James Foote

                      > Good. So how much detail?

                       

                      As much a you're willing to share.  I'd love the details, but even just an overview of the steps would help me learn more.

                       

                      > 1. How familiar are you with Google Earth?

                       

                      More than a beginning user, less than an expert user.  Never tried to code against it or extract datum from it.

                       

                      > 2. How familiar are you with Tableau?

                       

                      More than  than a beginning user, less than an expert user.  Trying to build my skills.

                       

                      > How familiar are you with background images in Tableau?

                       

                      I've been through the tutorials and I've read along with the 'Crowd Sourced WMS Server' thread by Allan Walker that addresses the idea in some detail.


                      > How familiar are you with trig?


                      I'm comfy with trig and generally with software development.


                      > Do you care 'why' it works? Or just how to get it to work?


                      I'm interested in both, but if I had to choose just one I'd say getting it to work is more important. On the other hand I've already consumed a bunch of your time and I don't want to be too big of a leach!


                      Should we take this discussion offline?  Or is it something that should get documented here?


                      Thanks!

                      • 8. Re: Re: Mapping arctic coordinates?
                        James Foote

                        Great stuff Shawn!

                         

                        I'm going to try to replicate your steps, I'll let you know if I run into any issues.

                         

                        Thanks again.

                        • 9. Re: Mapping arctic coordinates?
                          Allan Walker

                          Hi James,

                           

                          I think you'll need this datum:

                          EPSG:3408 NSIDC EASE-Grid North

                           

                          You'll also be wanting this WMS link.

                           

                          Source.

                           

                          There are a ton of SHP files from the NSIDC site if you wanted to create your own Geoserver WMS implementation of it; or you could just use a cascading WMS (proxy served) background from the link I gave above.

                           

                          Best Regards,

                           

                          Allan

                          • 10. Re: Re: Mapping arctic coordinates?
                            James Foote

                            Hi Allan,

                             

                            Thanks!  I'm stumbling around a bit here - can you give me an overview of the steps I need to take?

                             

                            My understanding from reading your Crowd Sourced WMS post is that the idea is to use a custom polygon map rather than either a background image or a map imported directly into Tableau via a WMS server. 

                             

                            I think the task is something like:

                            download and install Geoserver on the local host

                            download the EPSG:3408 NSIDC EASE-Grid North map and install it in my local Geoserver  (or maybe there's a way to configure my local Geoserver to act as a local proxy for the NSIDC wms server?)

                            from Tableau import the EPSG:3408 NSIDC EASE-Grid North map from my local Geoserver as a polygon map

                             

                            At that point would we expect Tableau to be able to place Lat/Lon points on the polygon map?  (Even though the map isn't a

                            WGS 84:4326 projection?)

                             

                            -- Jim

                            • 11. Re: Re: Mapping arctic coordinates?
                              James Foote

                              Hi Allan,

                               

                              > Can you see this?

                               

                              No, I'm getting this error:

                              Oops! Google Chrome could not connect to 129.123.25.124:8080

                               

                              Do I need to drill through a firewall somewhere? 

                               

                              -- Jim

                              • 12. Re: Mapping arctic coordinates?
                                Allan Walker

                                Yep, you'll need an incoming rule for 8080

                                 

                                You should see this:

                                 

                                Untitled.png

                                 

                                I will try to force this into Tableau this afternoon.

                                • 13. Re: Mapping arctic coordinates?
                                  James Foote

                                  Hi Allan,

                                   

                                  I've been dredging up my network troubleshooting skills from the distant past to try to sort access to the link you posted but I'm not making great progress.  You wrote:

                                   

                                  > Can you see this?

                                   

                                  That's a link to your geoserver, running on your machine with ip address 129.123.25.124 on port 8080 right? 

                                   

                                  When I try to access that link I get the chrome error:

                                  Oops! Google Chrome could not connect to 129.123.25.124:8080


                                  So I tried a couple of things:

                                  First try to telnet from my localhost to this server at port 8080, but I couldn't make a connection.  Hmm.

                                  So I try to ping that host from my localhost and I get no responses.  Hmm.

                                  Ok, so maybe there's some blocking in my local area net, or my ISP that's keeping me from connecting.  So I tried a remote ping server at Web-Based Remote Ping Tool | Wormly

                                  but it also didn't see a response to ping. 

                                  Hmm.  My guess is that the firewall that's blocking my access to your geoserver is at your end, not mine.  Have I got that right?

                                   

                                  You also wrote:

                                   

                                  > Yep, you'll need an incoming rule for 8080

                                   

                                  So maybe you were asking me to provide the info that you'd need to enable port forwarding at your end, to allow your localhost to accept connections from outside?  In that case maybe you meant for me to provide the IP address that my requests we going to arrive on?  If so I'm not sure how to answer since my localhost is behind a NAT'd network so I'm not sure what IP address your server would see for my requests.  But it seems unlikely that this is really what you meant!

                                   

                                  Alternately, that sentence would have made more sense to me if I was running my own geoserver on a host different from localhost.  In that case I can see how the firewall on the geoserver hosting machine would need an incoming rule to allow my localhost (running Tableau) to connect to it.  But maybe that's what you meant - that I should go ahead and setup my own geoserver (no problem, that's done), then configure it to do what your Geoserver is doing for you with the NSIDC maps. If so, any hints on how to do that geoserver configuration?

                                   

                                  'Sorry to be so dense!  And thanks for the help.

                                   

                                  -- Jim

                                  • 14. Re: Mapping arctic coordinates?
                                    Allan Walker

                                    Jim,

                                     

                                    Not dense at all.  Looks like my address is masked.

                                     

                                    Regardless, I was able to get the openlayer as above by cascading the WMS link on the NSIDC website.  However, it looks like the 3408 datum isn't supported in Tableau's WMS implementation, so I had a play around in QGIS to see what was going on.

                                     

                                    It looks like the way to go is to download the polygons from the site and build up a Google Mercator Layer.  Give me some time and I'll do that for you.

                                     

                                    But if you do your own Geoserver instance, you will need to create an outbound rule for 8080. so Tableau can see it, even if it is localhost!

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