6 Replies Latest reply on Jul 9, 2009 7:03 AM by guest contributor

    map coordinates

    . mongol

      Hi,

       

      After having created a map display, using the polygon shape feature, I would like to be able to export the image and register it in a different map. The reason is that I would like to overlay another data set, which currently is not possible.

       

      I have attached the image that I would like to be able to geo register as a base map for the next map display.

       

      Any ideas would be really appreciated.

       

      cheers, Adrian

        • 1. Re: map coordinates
          Joe Mako

          Check out the Jedi Training topics and jump to the maps section. He will show how to use this article: Map of the United States

           

          I did the same thing but with these values

          X Field

          Longitude

          Left:

          -88.59787


          Right:

          -87.30423


           

          Y Field

          Latitude

          Bottom:

          41.426253


          Top:

          42.454874


           

          I got these values by using Google Maps and dropping a pin to get the Lat/Lon of the Upper Left and Lower Right (42.454874,-88.59787 and 41.426253,-87.30423) as I saw in your image. Depending on exact you need this to be, you may need to play with the numbers.

           

          Here is the source data I used in the attached workbook:

           

           

          Lat, Lon, Place
          
           41.877741, -87.635193, Chicago
          


           

          Once connected, I dragged Lat and Lon up to the Dimension area, and changed them both to Geographic Role -> None from their right-click menus. I put Lon on the Columns shelf and Lat on the Rows shelf. Then using the menu option Data -> Background Images, I linked to your image and entered the above values. I also went the the Options tab and checked the box for Always Show Entire Image. I undisplayed the two axis headers and finally styled the mark.

           

          I hope this helps.

          • 2. Re: map coordinates
            . mongol

            Hi Joe,

             

            this is fantastic! It helps a lot.

            The point where I am stumbling is the Google Maps part: where you get the bounds for the map image.

            I realize that this might not be yet exposed by Tableau, but the bounds should be easily available within it since it displays the map.

             

            >>> I got these values by using Google Maps and dropping a pin to get the Lat/Lon

            >>> of the Upper Left and Lower Right (42.454874,-88.59787 and 41.426253,-87.30423) as I saw in your image.

            >>> Depending on exact you need this to be, you may need to play with the numbers.

             

            You mention 'dropping a pin': does this mean that you loaded the Illinois image in Google Maps and did the calculations over there. Any tips or a link would greatly help.

             

            many thanks, Adrian

            • 3. Re: map coordinates
              Joe Mako

              Adrian,

               

              By "dropping a pin" I mean, I went to http://maps.google.com and zoomed into the Chicago area in Map view (it was helpful that you had the roads displayed in your image). I right-clicked and selected "Directions to here" and dragged the pin around till I thought I had it about where the upper left corner of your image was, and dragged it again for the lower right. The left side of the screen displays the lat/lon coordinates.

               

              There may be a better way to do this, but I felt it worked easy enough for a one-off. If you have to do this process for a lot of exported images, I would recommend finding a better way. I have some ideas that I can flesh out if this is what you are looking for, but it would have to fit with your process and goals.

               

              Also, I would recommend exporting to a PNG instead of JPG, as a PNG format does not blur the image.

               

              Best Regards,

              Joe

              • 4. Re: map coordinates
                . mongol
                • 5. Re: map coordinates
                  Joe Mako

                  Adrian,

                   

                  Thank you so much for sharing.

                   

                  After trying this out, I would also add:

                   

                  If the Lat/Lon fields are not Generated, right-click the Lat/Lon fields in the Dimensions/Measures area and select "Set Default"->"Number Format" and set it to "Number (Custom)" with 5 Decimal Places (maybe more, depending on how precise you want to be).

                   

                  and

                   

                  once the point annotation is in place, select it and drag the point of the arrow fully into the corner.

                  • 6. Re: map coordinates
                    guest contributor

                    hi i am trying to find a site where i can find western coordinates useing the northern coordinates can u help please thanks n 55d /08m/44s