CtrEditor/ObjetosSim/ucTransporteTTop.xaml

<UserControl x:Class="CtrEditor.ObjetosSim.ucTransporteTTop"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:CtrEditor"
             mc:Ignorable="d" 
             DataContext="{Binding RelativeSource={RelativeSource Self}}">
    <Canvas>
        <Rectangle Width="{Binding Datos.Ancho}" Height="{Binding Datos.Alto}" Fill="Gray"/>
    </Canvas>
</UserControl>