Detect grid upon grid in XAML - xaml

Question

I have 2 Grids in XAML. One small and one big. How I can detect that, after first move, it upon second? I need smth like coordinates (need to align the first grid to the second grid's border or to other grids in this 'big-grid'). What're methods, properties?
<Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
<Grid HorizontalAlignment="Center" VerticalAlignment="Center" x:Name="Parent" Margin="124,340,1042,228">
<Grid.RowDefinitions>
<RowDefinition Height="100"/>
<RowDefinition Height="100"/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="100"/>
<ColumnDefinition Width="100"/>
</Grid.ColumnDefinitions>
<Grid Grid.Column="0" ManipulationDelta="Object_ManipulationDelta" x:Name="Figure" ManipulationMode="All">
<Rectangle Fill="Red" Width="40" Height="40"/>
<Rectangle Fill="Red" Width="40" Height="40" Margin="-10,30,70,30"/>
<Rectangle Fill="Red" Width="40" Height="40" Margin="-10,70,70,-10"/>
<Rectangle Fill="Red" Width="40" Height="40" Margin="-50,70,110,-10"/>
<Grid.RenderTransform>
<CompositeTransform/>
</Grid.RenderTransform>
</Grid>
</Grid>
<Grid x:Name="Field" Width="500" Height="700">
<Rectangle Fill="Black" Width="40" Height="40" Margin="10,10,450,650" StrokeThickness="1" Stroke="#FF1B1B1B"/>
<Rectangle Fill="Black" Width="40" Height="40" Margin="50,10,410,650" StrokeThickness="1" Stroke="#FF1B1B1B"/>
<Rectangle Fill="Black" Width="40" Height="40" Margin="90,10,370,650" StrokeThickness="1" Stroke="#FF1B1B1B"/>
<!--many rectangles-->
</Grid>
</Grid>
I move Grid Figure to Grid Field. In future I may be change rectangle to border.

Answer 1

To detect the relative position between Figure and Field, you can use something like that:
var transform= Field.TransformToVisual(Figure);
Point relativePosition = transform.TransformPoint(new Point(0,0));
relativeCoordinate will be the distance between the Top Left of Field and the Top left of Figure
if you want the absolute coordinate of the Grid you can do this:
var transform= this.TransformToVisual(Figure);
Point absolutePositionFigureGrid = transform.TransformPoint(new Point(0,0));