The data I'm using is from this set:
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:
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 Latitude Beginning Longitude Ending Latitude Ending Longitude 84.6 6.2 84.5 6.7
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.
It looks like the four corners are all at 65 N:
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.
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.
Yes, that's what I'm looking for. Thanks!
> 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?
Great stuff Shawn!
I'm going to try to replicate your steps, I'll let you know if I run into any issues.
I think you'll need this datum:
EPSG:3408 NSIDC EASE-Grid North
You'll also be wanting this WMS link.
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.
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?)
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 188.8.131.52 on port 8080 right?
When I try to access that link I get the chrome error:
Oops! Google Chrome could not connect to 184.108.40.206:8080
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.
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!