Comparison Tools
The following comparison tools are available:
§ Elevation Difference – 3D Mesh Layers
§ Elevation Difference – Elevation Layers
Swipe Snapshots
The Swipe Snapshots tool helps you create and compare snapshots showing different versions of the area in view in the 3D Window by showing or hiding objects in the Project Tree.
Swipe Snapshots Tool
To use the Swipe Snapshots tool:
1. In the 3D Window, navigate to the required area, and then create the required scene by using the Project Tree to show or hide objects.
2. On the Analysis tab, in the Comparison group, click the arrow under Swipe, and select Swipe Snapshots. When snapshot generation is complete, a Swipe Snapshots dialog box is displayed.
Create Modified Scene
3. Create a modified scene by showing or hiding objects in the Project Tree, and then click Compare.
4. When the snapshot is generated, use the following controls:
§ Mode selection – Selects the slider control mode. Choose between four clipping modes (right-left, left-right, top-bottom and bottom-top) and Transparency mode.
§ Slider control – Defines the clipping or transparency level extent. Slide the slider all the way to the left to completely show the first snapshot, and all the way to the right to completely show the second one. As the slider moves between these extremes, the first snapshot is gradually clipped or opacity decreased to reveal the second one.
Swipe Mesh, Point Cloud, and Imagery Layers
The Swipe Layers tool helps you detect the changes between two layers in the same location of any of the following types: mesh, point cloud, or imagery, or between one of these layer types and the base terrain. Using the tool, you can horizontally swipe between them, dynamically revealing and hiding parts of each layer.
Swipe Layers Tool
To use the Swipe Layers tool:
1. Zoom in on an area with two visible layers, or with a single layer that you want to compare to the base terrain.
2. On the Analysis tab, in the Comparison group, click the arrow under Swipe, and select Swipe Layers. The Swipe Layers controls are displayed.
3. Click any of the following: 3D Mesh, Point Cloud, and Imagery to filter the selection to the layer type(s) you want. If you want to refresh the drop-down layers, and automatically detect and select the layers in current view, click Refresh & Auto-Select.
4. Select the layers from the two drop-down lists, and click Start.
5. If comparing mesh model layers, select the mesh model display style:
§ Texture
§ Texture + wireframe
§ Solid color
§ Solid color + wireframe
§ X-ray - Semi-transparent model, enabling you to see through all model walls
6. Slide the slider all the way to the right to completely show the first layer, and all the way to the left to completely show the second one. As the slider moves between these extremes, the first layer is gradually clipped to reveal the second one.
7. Click Auto-Repeat 
to automatically loop the slider value between 0-100% to dynamically change the top layer clipping. Click Freeze at any point to freeze the slider at a specific value.
Elevation Difference – 3D Mesh Layers
The Elevation Difference – 3D Mesh Layers tool analyzes the elevation difference between two mesh layers in a defined polygonal area. This allows you to carefully compare between two layers and identify where there have been changes, e.g., for use in urban development to monitor compliance with building zone regulations and detect illegal construction.
The area for analysis is defined by a drawn polygon or by objects already on the clipboard. The output of the analysis is a point shapefile that stores the elevation difference information in its attribute fields and graphically represents the elevation difference at different points in the defined area. Only elevation differences that you consider significant for your analysis, i.e., that are above the Min Difference that you set, are marked:
§ Yellow – Layer 1 is higher than Layer 2
§ Cyan (Blue-green) – Layer 2 is higher than Layer 1
A summary is also generated, with statistics on the percentage of points in which each layer was higher and the maximum elevation difference between the two.
To use the Elevation Difference – 3D Mesh Layers tool:
1. On the Analysis tab, in the Comparison group, click the arrow under Elevation and select Elevation Difference – 3D Mesh Layers. The Elevation Difference – 3D Mesh Layers dialog box is displayed.
Elevation Difference – 3D Mesh Layers
2. Select the layers for comparison. If you want to refresh the drop-down layers, and automatically detect and select the mesh layers in current view, click Refresh & Detect.
3. Select the Quality of the result layer. This determines the accuracy level by which the analysis is performed. Select one of the following options:
§ Low – Performs approximately 16K samples
§ Medium – Performs approximately 65K samples
§ High – Performs approximately 260K samples
4. In the Min Difference field, select the minimum elevation difference between the layers that should be marked.
5. Select either of the following methods to mark your area of interest:
§ Draw Area – The area is marked by drawing a polygon in the 3D Window. If this option is selected, left-click in the 3D Window to place the polygon waypoints, and right-click to complete.
§ From Clipboard – Analysis is performed in the locations of all polygon clipboard objects. The polygons must be on the clipboard before selecting this option.
6. After the analysis is complete, a results dialog is displayed:
§ Number of sampled points for which the elevation difference between the layers was greater than the Min Difference set.
§ Number of sampled points above Min Difference in which Layer 1 was higher than Layer 2.
§ Number of sampled points above Min Difference in which Layer 2 was higher than Layer 1.
§ Maximum elevation difference in which Layer 1 was higher than Layer 2.
§ Maximum elevation difference in which Layer 2 was higher than Layer 1.
7. Review the elevation difference results, graphically represented by the generated point feature layer. Only elevation differences. that are above the Min Difference that you set, are marked:
§ Yellow – Layer 1 is higher than Layer 2
§ Cyan (Blue-green) – Layer 2 is higher than Layer 1
Point to any point on the graph to display the elevation and volume difference at that point.
8. The elevation difference results are automatically exported to a point shapefile that is listed in the Project Tree and saved under the application AppData. You can find the full path to this shapefile in the layer's property sheet, in the File Name property under the Layer tab.
9. If you want to compare further between the two mesh layers, on the Analysis tab, in the Comparison group, click the arrow under Swipe, and select Swipe Layers. Then use the Swipe Layers controls to horizontally swipe between the layers, dynamically revealing and hiding parts of each layer.
Elevation Difference – Elevation Layers
The Elevation Difference – Elevation Layers tool analyzes the elevation difference between two elevation layers or between an elevation layer and base terrain in a defined polygonal area. This allows you to carefully compare between two layers to contrast between the state of an area before and after a landslide or volcano, or to evaluate restorative efforts following mining activity.
The area for analysis is defined by a drawn polygon or by objects already on the clipboard. The output of the analysis is a point shapefile that stores the elevation difference information in its attribute fields and graphically represents the elevation difference at different points in the defined area. Only elevation differences that you consider significant for your analysis, i.e., that are above the Min Difference that you set, are marked:
§ Yellow – Layer 1 is higher than Layer 2
§ Cyan (Blue-green) – Layer 2 is higher than Layer 1
A summary is also generated, with statistics on the percentage of points in which each layer was higher and the maximum elevation difference between the two.
To use the Elevation Difference – Elevation Layers tool:
1. On the Analysis tab, in the Comparison group, click the arrow under Elevation and select Elevation Difference – Elevation Layers. The Elevation Difference – Elevation Layers dialog box is displayed.
Elevation Difference – Elevation Layers
2. Select two layers for comparison, or layer and base terrain. If you want to refresh the drop-down layers, and automatically detect and select the elevation layers in current view, click Refresh & Detect.
3. Select the Quality of the result layer. This determines the accuracy level by which the analysis is performed. Select one of the following options:
§ Low – Performs approximately 16K samples
§ Medium – Performs approximately 65K samples
§ High – Performs approximately 260K samples
4. In the Min Difference field, select the minimum elevation difference between the layers that should be marked.
5. Select either of the following methods to mark your area of interest:
§ Draw Area – The area is marked by drawing a polygon in the 3D Window. If this option is selected, left-click in the 3D Window to place the polygon waypoints, and right-click to complete.
§ From Clipboard – Analysis is performed in the locations of all polygon clipboard objects. The polygons must be on the clipboard before selecting this option.
6. After the analysis is complete, a results dialog is displayed:
§ Number of sampled points for which the elevation difference between the layers was greater than the Min Difference set.
§ Number of sampled points above Min Difference in which Layer 1 was higher than Layer 2.
§ Number of sampled points above Min Difference in which Layer 2 was higher than Layer 1.
§ Maximum elevation difference in which Layer 1 was higher than Layer 2.
§ Maximum elevation difference in which Layer 2 was higher than Layer 1.
7. Review the elevation difference results, graphically represented by the generated point feature layer. Only elevation differences. that are above the Min Difference that you set, are marked:
§ Yellow – Layer 1 is higher than Layer 2
§ Cyan (Blue-green) – Layer 2 is higher than Layer 1
Point to any point on the graph to display the elevation and volume difference at that point.
8. The elevation difference results are automatically exported to a point shapefile that is listed in the Project Tree and saved under the application AppData. You can find the full path to this shapefile in the layer's property sheet, in the File Name property under the Layer tab.