topic Plotting coordinates onto modified US Map in Graphics Programming

Plotting coordinates onto modified US Map

RandoDando — Wed, 22 Jul 2020 18:50:35 GMT

I am trying to use the map mapsgfk.Us which has AK and HI in the lower left. How do I go about plotting an annotate data set with normal X Y coordinates onto that? Some of those points are in AK and HI, so I want them to appear on the modified location of that map. An example would be helpful.

Re: Plotting coordinates onto modified US Map

ballardw — Wed, 22 Jul 2020 19:54:38 GMT

Please define what you mean by "normal X Y" coordinates in this sense.

With the scale of that map I would be tempted, if at all practical, to find the location of the nearest city in the USCity data set and use the coordinates from that for the annotate X Y coordinates.

Re: Plotting coordinates onto modified US Map

RandoDando — Wed, 22 Jul 2020 20:26:46 GMT

I should have elaborated. By normal coordinates I mean latitude and
longitude.

Re: Plotting coordinates onto modified US Map

GraphGuy — Thu, 23 Jul 2020 00:51:35 GMT

If city centroids would be close enough for your points, you could use the x/y coordinates in mapsgfk.uscity, and annotate those onto mapsgfk.us.

The 'tricky' part about mapsgfk.us is that Alaska and Hawaii are moved, resized, and projected differently than the 48 contiguous states. Therefore, in order for you to annotate your own arbitrary lat/long coordinates onto mapsgfk.us, you would need to know exactly how to move, resize, and project the coordinates.

I've found that the easiest way to do that is to "create my own" US map, with Alaska & Hawaii moved/resized/projected the way I want them, and then I know what values to apply to my annotated lat/long. Here is one example where I've done that:

http://robslink.com/SAS/democd75/best_restaurants_2014_info.htm

Re: Plotting coordinates onto modified US Map

RandoDando — Thu, 23 Jul 2020 14:48:28 GMT

Thanks! When I first tried this I had copied the code when going from the Contiguous set to Alaska to Hawaii, and made the necessary changes. I had omitted the NODATELINE option in the GPROJECT procedure which caused Alaska to be distorted. Adding that option fixed it.