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pan as my graphic tracker symbol moves

DarcyHathaway

I need help to make the map pan as my graphic tracker symbol moves based on the GPS feed.
I am using Arc Object 10 with VS.net VB.

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JeffMatson

I need help to make the map pan as my graphic tracker symbol moves based on the GPS feed.
I am using Arc Object 10 with VS.net VB.

The basic method would be to use IActiveView and IEnvelope. Each time your graphic tracker symbol moves, use IEnvelope.CenterAt() and reset your IActiveView.Extent to the updated Envelope, and then refresh.

DarcyHathaway

The basic method would be to use IActiveView and IEnvelope. Each time your graphic tracker symbol moves, use IEnvelope.CenterAt() and reset your IActiveView.Extent to the updated Envelope, and then refresh.

That will not work because the map refreshes every time the GPS changes this is every half a second. It causes the map to blip and is very ugly, not acceptable.

JeffMatson

That will not work because the map refreshes every time the GPS changes this is every half a second. It causes the map to blip and is very ugly, not acceptable.

There are many ways to refresh the map without the dreaded "blipping" but it depends on how you are going about things. Maybe if you post some more information or a code sample someone can help.

LeoDonahue

You could look at: com.esri.arcgis.carto.CenterAndScale

Graphics Tracker should be handling your refresh, right? You are not explicitly calling map.refresh are you?

DarcyHathaway

Yes, the graphic tracker is handling the refresh for the symbol and it moves perfectly but I need the map to pan as the symbol moves out of view to the user will not have to manually pan while driving.

here is my code.

I have a GPS that is running in the background getting the Lat and Long when it is changing and feeding.
This code below is running on a timer Me.Timer1.Interval = 500 and works great for the graphic tracker.
Sub Lat_Long(ByRef Latcoord As String, ByVal Longcoord As String)

        Dim activeView As IActiveView = TryCast(map, IActiveView)

        If Latcoord <> "" And Longcoord <> "" Then

            m_graphicTracker.Initialize(TryCast(map, IBasicMap))

            Dim gc As IGraphicsContainer
            gc = activeView

            ' Get the spatial reference of the map (UTM)
            Dim sr As ISpatialReference
            sr = activeView.FocusMap.SpatialReference

            '' Create a point and assign the geographic coordinate system (lat/long)
            Dim point As IPoint = New ESRI.ArcGIS.Geometry.Point

            ' Get the geographic coordinate system used by the map's spatial reference (lat/long)
            Dim geoSR As ISpatialReference
            Dim psr As IProjectedCoordinateSystem
            psr = sr
            geoSR = psr.GeographicCoordinateSystem

            point.SpatialReference = geoSR
            ' Give the point coordinates known to exist in the current extent
            point.PutCoords(Longcoord, Latcoord)
            point.Project(sr)

            If PointFirstTime = True Then
                'Get the Graphic Symbol
                Dim gtSymbol As IGraphicTrackerSymbol = m_GTSymbols(2)

                Dim id As Integer = m_graphicTracker.Add(TryCast(point, IGeometry), gtSymbol)

                m_GTGeometries.Add(0, TryCast(point, IGeometry))
                m_graphicTracker.Replace(0, m_GTGeometries(0), m_GTSymbols(2))

            End If

            If m_graphicTracker IsNot Nothing Then
                For i As Integer = 0 To m_graphicTracker.Count - 1
                    Dim id1 As Integer = i
                    If m_GTGeometries.ContainsKey(id1) Then
                        'Dim pnt As IPoint = DirectCast(m_GTGeometries(id), IPoint)
                        Dim pnt As IPoint = point
                        Dim x As Double = pnt.X
                        Dim y As Double = pnt.Y

                        m_graphicTracker.MoveTo(id1, x, y, 0)
                        m_GTGeometries.Remove(id1)
                        Dim point1 As IPoint = New ESRI.ArcGIS.Geometry.Point
                        point1.PutCoords(x, y)
                        m_GTGeometries.Add(id1, point1)

                        Try

                            If activeView Is Nothing Then
                                Return
                            End If

                            Dim screenDisplay As ESRI.ArcGIS.Display.IScreenDisplay = activeView.ScreenDisplay

                            'Here I am trying a couple of ways to get it to pan

                            Dim envelope As ESRI.ArcGIS.Geometry.IEnvelope = activeView.Extent

                            envelope.CenterAt(point1)
                            envelope.Expand(0, 0, True)

                            activeView.Extent = envelope
                            'This causes a blip
                            ' activeView.Refresh()

                            point.PutCoords(SaveLongCoord, SaveLatCoord)
                            point.Project(sr)
                            activeView.CenterAt(point)
                            'This causes a blip
                            'activeView.PartialRefresh(esriViewDrawPhase.esriViewGraphics, TryCast(basemapLayer, Object), Nothing)


                        Catch ex As Exception

                        End Try

                    End If
                Next
            End If

            PointFirstTime = False

        End If

    End Sub

JeffMatson

You might need to cache your layers (not sure what type of layer 'basemapLayer' is) to avoid the blips.

Also since you have an envelope, pass that into partialRefresh. Lastly you might need to change the draw phase being passed into partialRefresh (you can also combine several draw phases)

Hope that helps

DarcyHathaway

I am creating this in a window application.

I tried activeView.PartialRefresh(esriViewDrawPhase.esriViewBackground, Nothing, envelope) and it is not working.

LeoDonahue

partial refresh is not working or it is not giving you the effect you wanted?

DarcyHathaway

It is not giving me the effect I want.

I really need the map to pan to the point as the point moves.

LeoDonahue

Did you try using this class? com.esri.arcgis.carto.CenterAndScale

DarcyHathaway

The class com.esri.arcgis.carto.CenterAndScale looks like it is for Java and I am creating this in a windows PC application.

LeoDonahue

Oh my mistake.

http://resources.arcgis.com/en/help/arcobjects-net/componenthelp/0012/0012000002sm000000.htm

Brooks_SummitGeo_0-1626760177895.png

DarcyHathaway

Yes I have tried that and that is what is causing the blip because of the refresh.

DarcyHathaway

I took a closer look at the CoClasses and Classes that you sent me to look into and I cannot use this because it too is for a web application using a Mapserver and I am creating this application for a windows PC application using a Geo database.

LeoDonahue

Take a closer look.

Provides access to the Center And Scale Map Area Interface.

Product Availability Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server.

LeoDonahue

Sorry Darcy, that example uses MapServer, why? I have no idea. But it will work with desktop.

And, I thought you said that this solution causes a blip anyway?

DarcyHathaway

Well I had to take a closer look and see if I was missing something.

I am not using desktop either, I am using Visual Studio .net.

Do you have an example?

LeoDonahue

So.... that leaves us with ArcGIS Engine? And that class is still supported there also.

DarcyHathaway

And yes ArcGIS Engine is what i am using.

Okay please help me figure out if it will work.

Do you have an example?

LeoDonahue

Sadly, I program in Java and I my sample I would give you is for a MapServer, BUT....

It is really very easy.

You can probably translate this to .NET, I have faith in you.

Create a CenterAndScale object. Use the method to center that accepts a point. Assign it your GPS point.
Set the map extent to the CenterAndScale extent.
Refresh... .and there is your blip.

You have to refresh your map, the other layers have to draw, even when you pan/zoom.

Jeff Matson already pointed this out. You can do things like partial refresh, or set map cache for your layers, or you can dissolved your data so that it draws really fast.

You mention that you are getting a GPS point two times per second. That is really fast, why so fast?

What you could do is use a timer to refresh your map every 5 or 10 seconds, and let the GPS tracker still plot away with the graphics. If your map display shows enough area for a 2 or 3 mile range, I don't think your drivers will be able to drive faster than that distance in 5 or 10 seconds, but I don't know them personally.

DarcyHathaway

The reason it is so fast is because this is an application for a helicopter and emergency vehicles and the point must move as fast as possible. The application shows them directions and the point must follow the line to the destination. If the map it zoomed out to far then the driver will not see the details of the direction line on the road.

I think a partial refresh should work too but I can�??t get it to work for me, I am sure I am doing something wrong with the syntax.

It seems to me that this has to be possible without the blip. The graphic tracker it supposed to work for 3D too and you would want the map to pan as it moved.

DavidClarke1

I have been trying to use the GraphicsTracker for a similar purpose. When I add graphics to the graphic tracker, I get a flashing effect when any of the map layers have labels turned on. If I turn off the labels for those layers, then the flashing goes away.

Also, enabling Dynamic Display will stop the flashing but there are many known limitations with Dynamic Display. See the link.

http://resources.arcgis.com/en/help/arcobjects-net/conceptualhelp/index.html#//00010000004t000000

DarcyHathaway

You should only have to create the graphic once and then just move the graphic. The graphic tracker won�??t refresh the screen as it moves.

My blip is only when trying to pan the point to the center of the screen.

DavidClarke1

I do create the graphic once and then move the graphic. The graphic tracker graphics do get refreshed because labeling and graphics are drawn in the same drawing phase. This happens when I pan the map.

I have an open incident with ESRI regarding this.

LeoDonahue

Maybe ArcGIS Desktop is not the right solution for map refreshes every 0.5 seconds for you.

DarcyHathaway

I am now getting the same issue happening with the labels and the trackers graphic; let me know what you find out.

If the tracker graphic and the labels were working independently it would be working perfect.

DavidClarke1

I only mentioned these things because I am also using the GraphicsTracker for an application receiving constant GPS data and I support a function that "follows" a graphic around the map as it moves. Essentially the same thing as dachenbach.

The blip mentioned sounded like the flashing I see but perhaps it is different.

DarcyHathaway

Maybe ArcGIS Desktop is not the right solution for map refreshes every 0.5 seconds for you.

I am using Arc Engine

DarcyHathaway

I only mentioned these things because I am also using the GraphicsTracker for an application receiving constant GPS data and I support a function that "follows" a graphic around the map as it moves. Essentially the same thing as dachenbach.

The blip mentioned sounded like the flashing I see but perhaps it is different.

DavidClarke1

Although I am not giving up, here is part of the response from ESRI support.

It is recommended that not to use labels when using the GraphicTracker to display moving points. For performance reasons the Graphics in the GraphicTracker draw in the same phase as labels. Therefore labels may conflict with the graphics, cause flickering, and slowdown the overall performance of the GraphicTracker.

I don't understand this since the graphics themselves are drawn on top of everything else on the map. The placement of labels (for map layers) and graphics on the tracker do not position themselves in relation to each other to improve visibility. The graphics are always drawn exactly where you tell them.

The only other thing I can think of is to use annotation layers instead of standard dynamic map labels. The problem is that takes time to do and many of my users would not know how to do this.

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