Validating Geometries with Z Values

GeoMedia Fusion 6.0 has a useful command - Advanced Validate Geometry to validate and correct 3-D geometries like contour lines, drain lines, lakes etc. before loading into GeoMedia Terrain geomorphic datastores. The command can detect the following anomaly types with regards to the Z values:

• Area not closed in Z-plane
• Z out of range
• Not monotonic
• Not flat
• Z breaks

Area not closed in Z-plane Anomaly Check
This anomaly check is great for validating polygons to ensure that the first and last points are vertically closed i.e. have the same Z value.

Z Out of Range Anomaly Check
The Z out of range check will ensure that the geometries fall within a specified minimum and maximum range.

Not Monotonic Anomaly Check
Useful for validating geometries representing drainage lines; this will verify that the geometries have uniformly increasing or decreasing Z coordinates.

Not Flat Anomaly Check
Good for validating flat geometries such as lake polygons, contour lines.

Z Spike Anomaly Check
This check will look for spikes or abrupt changes in the Z coordinates of geometries.

Z Break Anomaly Check
A Z break refers to consecutive points of a geometry on the same XY position but with different Z coordinate.

Using the Advanced Validate Geometry Command

1. From the GeoMedia Professional pulldown menu, select Fusion > Advanced Geometric Validation > Validate Geometry.
   
   The Advanced Validate Geometry dialog box appears.
   
   
   
2. In the Input tab, toggle on the features you want to validate.
3. Click the Anomalies tab.
4. Expand the Anomaly Types node and toggle on the Z (height) checks you want to validate for.
   
   
   
   
5. Select a Z (Height) anomaly type check e.g. Z Out of Range and define the Anomaly Properties e.g. Minimum Z. For some anomaly types, there would be an option to auto-fix the anomaly.
   
   
   
   
6. Click the Output tab.
   
   
   
   
7. Type in the name of the queue and/or the name of the query.
8. Click OK to start the validation process.
   
9. You can use the Queued Edit command to review the validation results and correct the geometries using GeoMedia Professional's commands if necessary.
   

Elevation Tagging with GeoMedia

It is actually very simple to do elevation tagging with GeoMedia and you don't have to use GeoMedia Professional. I'm going to show you how to setup GeoMedia to do it.

For instance, you may have contour vector lines that you want to tag with elevations as part of a digital terrain workflow. The contours feature class needs to have an attribute field for storing the elevation; if it doesn't have, you can use the Feature Class Definition command to create one. Next, find out the elevation range and interval of the contours, say from 0 to 4500.

1. Select Legend > Add Thematic Legend Entry.
   
   The Add Thematic Legend Entry dialog box appears.
   
   
2. In the Input feature combo box, select the contours feature.
3. Choose Unique Value Thematic type.
   
4. In the Attribute for classification combo box, select the elevation attribute field.
5. Define the Style, Value, and Label for each contour elevation you have, e.g. 0, 500, 1000, ... 4500.
   
   Note: Choose colors that you can distinguish easily from the untagged contours, e.g dull earth colors. You could also choose bold black colors for major elevations and gray colors for intermediate elevations so you can see patterns in the map window.
   
   
6. Define the Style for the Other values.
   
   Note: This style is used for unassigned contours, so choose a contrasting color e.g. red that can be easily distinguished from the tagged contours.
   
   The Add Thematic Legend Entry dialog box may look like this.
   
   
   
7. Click OK.
   
   The Legend and the map window displays the newly created thematic mapping.
   
   Note: The unassigned contours are displayed in red and are easily distinguished from the tagged contours.
   
   
8. Double click on the unassigned contours.
   
   The properties dialog box appears.
   
   
9. Type in the elevation value and press OK.
   
   The newly tagged contours feature no longer displays in the untagged style.
   
   
10. Continue to assign elevation to all untagged contours until finished.
    

After you have completed the elevation tagging, you can use the Functional Attributes command or the Update Attributes command to update the contours feature class' geometries with the newly assigned elevation attribute.

Edit Reference Grid Labels

GeoMedia's Insert Reference Grid and Insert Cartographic Grid commands can add grids and other grid related marks and annotation into the layout window, as shown in the figure below. All the graphics created by the commands are grouped as a single entity. The components of the group cannot be edited and there is no "ungroup" command in the layout window to drop the grid into its component elements. What if the commands cannot create the labels not in the right production format. e.g. reference grid labels with zeros in front of the numerals - A01, A02, .... A10? Here I describe a workaround to the problem. In essence, the workaround approach is to select the component element, cut and paste it back from the clipboard, and finally editing the copy to the desired format.

1. Use the Selection Tool and hover the cursor over the annotation you want to edit.
   
   The NW Arrow cursor with three ellipsis appears.
   
   
2. Click once on the annotation.
   
   The PickQuick toolbox appears.
   
   
   
3. In the PickQuick toolbox, click the highest number.
   
   The component annotation is selected.
   
   
   
4. Press CTRL-x.
   
   The component is moved to the Windows clipboard.
   
   
   
5. Press CTRL-v.
   
   The component is pasted back to the layout window in the same position.
   
   
6. Now double click on the component. You should see an insertion point cursor in the annotation. If not, try again until you do.
   
7. Type in the desired text, e.g. 09.
   
8. Click anywhere else in the layout window to complete the edit.
   
   The annotation has been changed to the desired format.
   
   

There you go. Hope this is useful to somebody.

Using Update Attributes to Set Contour Elevation

An alternative method to set the elevation value of a contour line is to use GeoMedia's Update Attributes.

1. Use the Selection Tool to select one or more contour lines with the same elevation.
   
2. From the GeoMedia's pulldown menus, select Edit > Attribute > Update Attributes.
   
   The Update Attributes dialog appears.
   
   
   
3. In the Update Attributes dialog, expand the Select Set nodes and select the feature name.
   
4. On the right side of the Update Attributes dialog, click in the Value field of the feature's geometry field, e.g. LinearGeometry.
5. Click Expression.
   
   The Expression dialog box appears.
   
   
   
6. In the Categories list box, click Geometry.
7. In the Functions list box, double click the function SETZ.
8. In the Attributes list box, double click the attribute Input.{GeometryFieldName} e.g. Input.LinearGeometry.
   
   The Expression field should read like this:
   SETZ(Input.LinearGeometry)
   
   
9. Type in a comma before the closing parentheses.
   
10. Type in the elevation to set in the Expression field, e.g. 1000. The elevation should be in the units of the GeoWorkspace Coordinate System's Vertical Storage Unit.
    
    The Expression field should now read something like this:
    SETZ(Input.LinearGeometry,1000)
    
    Note: If the elevation you want to type in is not in the Coordinate System's Vertical Storage units, then you will have to do a conversion yourself.
    
    
11. Click OK.
    
    The selected contour line's elevation is adjusted to the new elevation.
    

Setting the Elevation of Contours using Edit Geometry

One of the common tasks in the terrain modeling workflow is to interactively tag vector contour lines with an elevation. I could not find a command in GeoMedia Terrain 6.0 or any steps in the delivered documentation. I could do the job with GeoMedia's Functional Attributes but I have to calculate the elevation values manually taking into account the storage units and my height unit preference - that would definitely scare users away. I later found out that I could also use GeoMedia Professional's Edit Geometry command. Here are the steps to tag contour lines with elevation with the Edit Geometry command.

1. Activate the Selection Tool.
   
2. Select a contour line geometry in the map window.
   
   
   
3. In the GeoMedia Professional Edit pulldown menu, select Edit > Geometry > Edit.
   
   All the vertices in the contour line are displayed as black handles.
   
   
   
4. Click on a vertex handle on the contour line to select it.
   
   The selected vertex is displayed as a purple filled circle.
   
   
   
5. Right click in the map window to bring up the Edit Geometry context menu.
   
   
   
6. Choose Select All.
   
   All the vertices are selected and are displayed with purple filled circles.
   
   
7. Right click again in the map window to bring up the Edit Geometry context menu again.
   
8. This time, choose Edit Height.
   
   The Edit Height dialog appears.
   
   
9. In the Edit Height dialog, type in the height value.
   
10. Click OK.
    
    The height of the contour line is changed to the new value.
    
    
11. Press ESC.
    
    The Edit Geometry command is deactivated.
    

The good points about Edit Geometry are that the height units follow the user's preferences set and the height changes can be undone. On the downside, the workflow is still a little cumbersome having to select all the vertices (which take a while if a contour line has a lot of vertices). I just might decide to write a GeoMedia custom command just to set the elevation of geometries.

GeoMedia Terrain 6.1 Released

Intergraph has just released a new version of GeoMedia Terrain version 6.1 in April. According to the release notes, this release is for delivering a version of GeoMedia Terrain that is compatible with GeoMedia 06.01.00. Enhancements in the new version include:

• Performance improvements
• The ability to take in larger data volumes than version 6.0
• New Primary InterOp Assemblies for .NET application development
• Windows Vista support and 64-bit hardware compatible
  

I have encountered poor performance and inexplicable crashes while writing a training course guide for GeoMedia Terrain. I have just ordered a copy of the software and once I receive the DVD, I hope to give the new version the run through and see whether Intergraph has fixed the problems.