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plotting - Implementing GeoCallout?


Building off of a related question, I'm looking for a robust way of using Callouts for multiple locations in Geography. For example, I want to plot cities and their names with arrows and text:



data = CloudGet @ CloudObject[
   "https://www.wolframcloud.com/objects/cb8f1216-74dd-463e-85a4-e976b6fd3fd4"];    
GeoListPlot[MapThread[
  Callout[#1, #2, CalloutMarker -> "Arrow", "CalloutStyle" -> Red] &, 
  data], GeoBackground -> "ReliefMap", GeoRange -> "World"
 ]

enter image description here


Clearly, Callout's are not supported in GeoGraphics (and don't issue any warnings if you didn't know that). However, my approach is to fake it by using Callout's in a ListPlot and overlay on top of a blank GeoGraphics map background:


bg = GeoListPlot[{}, GeoBackground -> "ReliefMap", 

   GeoRange -> "World"];
plain = {Reverse@*First /@ data[[1]], data[[2]]};
Overlay[{bg, 
  ListPlot[MapThread[
    Callout[#1, #2, "CalloutStyle" -> Directive[Thick, Red]] &, 
    plain], PlotRange -> {{-180, 180}, {-90, 90}}, Axes -> None, 
   PlotRangePadding -> Scaled[0]]}]

enter image description here


I can't get things to line up exactly for various GeoProjection's, and so that's what I'm looking for help with.



Update for Comment


It is different from this related question, because that solution doesn't look good for some reason here:


enter image description here


Final Update


Thanks @carlwoll, that solves it. However, my formatting of the Mollweide project isn't working as expected. Specifically, I'd like higher resolution (and less label collision if possible). But setting GeoZoomLevel -> 4 gets wiped out in the Show. I'd also like the callouts to look like this last example from ref/CalloutMarker:


ListLinePlot[{Callout[Fibonacci[Range[6]], "Fibonacci", {4, 10}, 5, 
   CalloutMarker -> Arrowheads[0.04], CalloutStyle -> Red], 
  Table[LucasL[n], {n, 6}]}]

enter image description here



Here's your code with my formatting tweaks:


bg = GeoListPlot[{}, GeoBackground -> "ReliefMap", 
   GeoRange -> "World", GeoProjection -> "Mollweide", 
   GeoZoomLevel -> 4];
plain = {First@
    GeoGridPosition[GeoPosition[data[[1, All, 1]]], "Mollweide"], 
   data[[2]]};
Show[bg, ListPlot[
  MapThread[
   Callout[#1, #2, Appearance -> "CurvedLeader", LeaderSize -> 20, 

     CalloutMarker -> "Arrow", 
     LabelStyle -> 
      Directive[FontFamily -> "Verdana", FontSize -> 12, 
       FontColor -> Red], CalloutStyle -> Red] &, plain], 
  Axes -> None, PlotRangePadding -> Scaled[0], 
  PlotStyle -> Directive[PointSize[0.005], Red]], 
 Options[bg, PlotRange], ImageSize -> 500]

enter image description here



Answer




Just use Show instead of Overlay:


Show[
    bg,
    ListPlot[
        MapThread[
            Callout[#1,#2,"CalloutStyle"->Directive[Thick,Red]]&,
            plain
        ],
        PlotRange->{{-180,180},{-90,90}},
        Axes->None,

        PlotRangePadding->Scaled[0]
    ]
]

enter image description here


An example using a different projection, where the conversion to grid coordinates is more complicated than just using Reverse:


bg = GeoListPlot[
    {},
    GeoBackground->"ReliefMap",
    GeoRange->"World",

    GeoProjection->"Mollweide"
];
plain = {
    First @ GeoGridPosition[GeoPosition[data[[1, All, 1]]], "Mollweide"],
    data[[2]]
};
Show[
    bg,
    ListPlot[
        MapThread[Callout[#1, #2, "CalloutStyle"->Directive[Thick,Red]]&, plain],

        Axes->None, PlotRangePadding->Scaled[0]
    ],
    Options[bg, PlotRange]
]

enter image description here


For your updated question


Sometimes some of the other GeoGraphics options need to be included in the Show call, so simplest would be to include them all. This will fix your GeoZoomLevel issue. As for improving label collisions, the size of the ListPlot will control how many callouts are generated. So, adjust the size with the ImageSize option. Examples:


bg = GeoListPlot[{}, GeoBackground -> "ReliefMap", 
    GeoRange -> "World", GeoProjection -> "Mollweide", 

    GeoZoomLevel -> 4
];
plain = {
    First@GeoGridPosition[GeoPosition[data[[1, All, 1]]], "Mollweide"], 
    data[[2]]
};

Your example, including all GeoGraphics options:


Show[
    bg,

    ListPlot[
        MapThread[
            Callout[#1, #2, Appearance -> "CurvedLeader", 
                LeaderSize -> 20, CalloutMarker -> "Arrow",
                LabelStyle -> Directive[FontFamily -> "Verdana", FontSize -> 12, FontColor -> Red],
                CalloutStyle -> Red
            ]&,
            plain
        ], 
        Axes -> None, PlotStyle -> Directive[PointSize[0.005], Red]

    ], 
    Options[bg],
    ImageSize -> 500
]

enter image description here


Shrink the ListPlot image size to reduce the number of callouts:


Show[
    bg,
    ListPlot[

        MapThread[
            Callout[#1, #2, Appearance -> "CurvedLeader", 
                LeaderSize -> 20, CalloutMarker -> "Arrow",
                LabelStyle -> Directive[FontFamily -> "Verdana", FontSize -> 12, FontColor -> Red],
                CalloutStyle -> Red
            ]&,
            plain
        ], 
        Axes -> None, PlotStyle -> Directive[PointSize[0.005], Red],
        ImageSize -> 250

    ], 
    Options[bg],
    ImageSize -> 500
]

enter image description here


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