topic Re: how to Zoom to point? in ArcGIS API for Silverlight Questions

how to Zoom to point?

StefhanCampos — Mon, 27 Sep 2010 14:01:40 GMT

Hi, i am trying zoom to a point in map, but doesn't work, i know cannot zoom to a point, and need make a new extent but how i can do that with silvelright api?

Re: how to Zoom to point?

JMcNeil — Sat, 11 Dec 2021 14:01:37 GMT

Like a bookmark?
Check out http://help.arcgis.com/en/webapi/silverlight/samples/start.htm#NavigationActions

 <Button Style="{StaticResource MenuItem}" 
                            Content="Zoom To" >
                        <i:Interaction.Triggers>
                            <i:EventTrigger EventName="Click">
                                <esri:ZoomToAction
                                    TargetName="MyMap">
                                    <esri:ZoomToAction.Geometry>
                                        <esri:Envelope XMin="-110" YMin="40" XMax="-100" YMax="50" />
                                    </esri:ZoomToAction.Geometry>
                                </esri:ZoomToAction>
                            </i:EventTrigger>
                        </i:Interaction.Triggers>
                    </Button>

Re: how to Zoom to point?

Charles__Jamie_Phillips — Sat, 11 Dec 2021 14:01:39 GMT

Here is a code example on how to zoom to a point. Why does it not work for you?

MapPoint myPoint = new MapPoint(x, y, spatialRef);

MyMap.ZoomTo(myPoint);

or you can do it like in the interactive sdk example for the "Find an Address" example.

Re: how to Zoom to point?

StefhanCampos — Mon, 27 Sep 2010 16:14:40 GMT

I want zoom a point(like image bottom), a point dont have start and end, when i zoom geometry, nothing happens, because dont have start and end, i suppose

Re: how to Zoom to point?

JenniferNery — Mon, 27 Sep 2010 17:10:56 GMT

You can use the following code, where mapPoint is the point geometry you want to zoom to.
MyMap.ZoomToResolution(MyMap.Resolution / MyMap.ZoomFactor, mapPoint);

Re: how to Zoom to point?

dotMorten_esri — Sat, 11 Dec 2021 14:01:42 GMT

The above code only zoom "around" that point (meaning that's the point that will stay at the same place on the screen, similar to a double-click zoom where the point you clicked stays at the same position).
I'm guessing you want to the point centered on the screen?

As you found out, you cannot zoom to a point, since a point has an infinitely small extent. The map simply doesn't know how far in you want to zoom. If the point represents an address, you probably want to zoom further in than if the point represents a city.

You can zoom to a point by constructing an extent around the point. ie.

Envelope env = new Envelope(p.X - 500, p.Y - 500, p.X + 500, p.Y + 500);
MyMap.ZoomTo(env);

In this example if the map units are meters, it would zoom to a 1kmx1km box centered on the point 'p'. Based on your map units and the scale you want to zoom to, you probably want to use a different number.

Alternatively you can just pan to the point: Ie: MyMap.PanTo(p);

Re: how to Zoom to point?

ducksunlimited — Sat, 11 Dec 2021 14:01:45 GMT

The above code only zoom "around" that point (meaning that's the point that will stay at the same place on the screen, similar to a double-click zoom where the point you clicked stays at the same position).
I'm guessing you want to the point centered on the screen?

As you found out, you cannot zoom to a point, since a point has an infinitely small extent. The map simply doesn't know how far in you want to zoom. If the point represents an address, you probably want to zoom further in than if the point represents a city.

You can zoom to a point by constructing an extent around the point. ie.
Envelope env = new Envelope(p.X - 500, p.Y - 500, p.X + 500, p.Y + 500);
MyMap.ZoomTo(env);
In this example if the map units are meters, it would zoom to a 1kmx1km box centered on the point 'p'. Based on your map units and the scale you want to zoom to, you probably want to use a different number.

Alternatively you can just pan to the point: Ie: MyMap.PanTo(p);

I used the points from a FINDTASk - but couldn't make it work. here are the codes, Any suggestions would be appreciated!

FindResult findResult = (FindResult)FindDetailsDataGrid.SelectedItem;
Graphic graphic = findResult.Feature;
ESRI.ArcGIS.Client.Geometry.Envelope selectedFeatureExtent = new ESRI.ArcGIS.Client.Geometry.Envelope(graphic.Geometry.Extent.XMin, graphic.Geometry.Extent.YMin, graphic.Geometry.Extent.XMax, graphic.Geometry.Extent.YMax);
MyMap.ZoomTo(selectedFeatureExtent);

Re: how to Zoom to point?

ducksunlimited — Mon, 27 Sep 2010 19:55:43 GMT

I used the points from a FINDTASk - but couldn't make it work. here are the codes, Any suggestions would be appreciated!

FindResult findResult = (FindResult)FindDetailsDataGrid.SelectedItem;
Graphic graphic = findResult.Feature;
ESRI.ArcGIS.Client.Geometry.Envelope selectedFeatureExtent = new ESRI.ArcGIS.Client.Geometry.Envelope(graphic.Geometry.Extent.XMin, graphic.Geometry.Extent.YMin, graphic.Geometry.Extent.XMax, graphic.Geometry.Extent.YMax);
MyMap.ZoomTo(selectedFeatureExtent);

OK, I made it work by adding and subtracting a number for X and Ys

thanks for the codes

Re: how to Zoom to point?

DominiqueBroux — Sat, 11 Dec 2021 14:01:48 GMT

You might also be interested by a centerAndZoom function:

 
private void centerAndZoom(ESRI.ArcGIS.Client.Map map, ESRI.ArcGIS.Client.Geometry.MapPoint mapPoint, double resolution)
{
double ratio = 1.0;
if (map.Resolution != 0.0)
ratio = resolution / map.Resolution;
 
if (ratio == 1.0)
map.PanTo(mapPoint);
else
{
ESRI.ArcGIS.Client.Geometry.MapPoint mapCenter = map.Extent.GetCenter();
double X = (mapPoint.X - ratio * mapCenter.X) / (1 - ratio);
double Y = (mapPoint.Y - ratio * mapCenter.Y) / (1 - ratio);
map.ZoomToResolution(resolution, new ESRI.ArcGIS.Client.Geometry.MapPoint(X, Y));
}
}

You can use it to center on a point and zoom to a given resolution.

For example

centerAndZoom(MyMap, pt, MyMap.MinimumResolution * 4);

Re: how to Zoom to point?

ChuckDavidson — Sat, 11 Dec 2021 14:01:50 GMT

You might also be interested by a centerAndZoom function:

 
private void centerAndZoom(ESRI.ArcGIS.Client.Map map, ESRI.ArcGIS.Client.Geometry.MapPoint mapPoint, double resolution)
{
double ratio = 1.0;
if (map.Resolution != 0.0)
ratio = resolution / map.Resolution;
 
if (ratio == 1.0)
map.PanTo(mapPoint);
else
{
ESRI.ArcGIS.Client.Geometry.MapPoint mapCenter = map.Extent.GetCenter();
double X = (mapPoint.X - ratio * mapCenter.X) / (1 - ratio);
double Y = (mapPoint.Y - ratio * mapCenter.Y) / (1 - ratio);
map.ZoomToResolution(resolution, new ESRI.ArcGIS.Client.Geometry.MapPoint(X, Y));
}
}

You can use it to center on a point and zoom to a given resolution.

For example

centerAndZoom(MyMap, pt, MyMap.MinimumResolution * 4);

Center and Zoom needs to be modified for couple of reasons
- need to compensate for center when current resolution is already less than minimum resolution
- need to compensate for center when current extent envelope does not contain the input point

private void centerAndZoom(ESRI.ArcGIS.Client.Map map,

ESRI.ArcGIS.Client.Geometry.MapPoint mapPoint, double resolution)
        {
            ratio = resolution / map.Resolution;

            if (Math.Round(map.Resolution,5) <= Math.Round(map.MinimumResolution,5))
                map.PanTo(mapPoint);
            else
            {
                map.PanTo(mapPoint);
                ESRI.ArcGIS.Client.Geometry.MapPoint mapCenter = map.Extent.GetCenter();
                double X = (mapPoint.X - ratio * mapCenter.X) / (1 - ratio);
                double Y = (mapPoint.Y - ratio * mapCenter.Y) / (1 - ratio);
                map.ZoomToResolution(resolution, new ESRI.ArcGIS.Client.Geometry.MapPoint(X, Y));
            }

        }