Wondering why discussing Intergraph Geomedia? It is true that in France
it has an almost confidential diffusion. But it does not deserve this. Besides the
fact that it has been the forerunner in many fields (the Esri geodatabase is
only the Intergraph Warehouse updated for Esri, but 10 years later), regarding
our interest, it is the proof that a lot more can be done when we really want. Let’s
see how geometry validation works with Geomedia 2014.
The documentation
In previous articles we have discussed the deficiency of documentation relating the geometry checks. Here we have 34 pages with definitions and examples. You can download here the part of the document “Geomedia Fusion Training Guide” regarding the geometry validation.
A small example that will make you want to download the document: “Backspace: Applies to linear or polygon features when the geometry is doubled backward on itself.
The line above is defined by a sequence of 10 nodes
(ABCDCDEFGH). The DCD sequence itself
defined as a backtrack.
Backtracking is corrected by removing the nodes
which constitute it. In the example above the second group of nodes
C and D are removed.
The line is then defined by a series of 8 nodes
(ABCDEFGH). This one is a simple example simple of
backtracking … “
The Validate Geometry command from Geomedia The command is located in the ribbon corresponding to the Toolbox Menu
You will find three tabs: Entry , Anomalies , and Result . The first tab is used to define the layer or layers to be validated.
Therefore you can define all the layers you want to perform validation without having to go through one at a time.
The Anomalies tab is used to indicate which anomalies to look for. They are grouped under three headings:
- Standard
- Specialized
- Z (height)
The right window makes it possible to configure the action to perform if the anomaly is found:
You can indicate, for each anomaly supported by the automatic correction, whether you want to apply it or not. The two commands, separated in the other software, are associated. Finally, the last tab allows you to configure the display of the results:
Placing anomalies in a queue will allow performing the manual corrections very easily.
Placing the anomalies in a query allows you to have a layer with the entities with anomalies, for example to see the made automatically corrections.
We will execute the command by selecting, only, all the standard anomalies and leaving the automatic correction disabled for all. The result is as follows:
Unlike the previous examples, Geomedia detects 28 anomalies instead of the 19 found in the previous examples.
In fact, it finds 19 entities with anomalies, but there are some that contain more than one anomaly. If you look at the highlighted record you will notice that the first of 5 records concern the same entity.
[In previous cases, when an entity is marked as invalid, the search stops. Though not the corrections. If we replay the test on the corrected entities, we see that there are no anomalies left. The corrector deals with all the anomalies of the same entity.] In the left window you will find the details of the anomalies. By clicking on a record you will, automatically, find the anomaly displayed on the left window. The usual editing commands allow you to manually correct the desired anomalies.
If you edit an anomaly in the left window, it disappears from the right window.
The example of the screen capture above shows an anomaly with an inner ring. As we have indicated in a previous example, this type of anomaly will be corrected automatically by creating an outer ring and an inner ring. We, also, indicated that it was not necessarily the best solution. Obviously, here the point that closes the water inlet should be separated, so as to form a creek and not a closed basin.
With Geomedia, it is easy to move the point and manually correct the anomaly, with the right solution.
Once we have finished with the manual corrections, we can re-execute the command, but by selecting the automatic corrections in the parameter window. In this case, the anomalies do not appear anymore.
In addition to the Validate Geometry command, Geomedia has another command: VOID Surface Detection that detects overlays or spaces between contiguous polygons.
The command simply asks for the layer to validate and where to place the detected surfaces. The result is then:
Thus, we have discussed all the possibilities with Geomedia. When reading the different articles you will understand, we have a small preference for this one, when it comes to validate the geometry of layers. We know what we do, we see what we correct and everything remains at a level of difficulty quite within our reach …
But you will ask us, what’s up with QGis? Well, that will be the topic of our next article.
You don’t have to create a whole new feature in GeoMedia, the buffer is just a representation of the feature that happens in the GeoWorkspace document. A buffer becomes a query in your legend that you can modify. You can actually change the buffer distance you just did and merge other buffers together on-the-fly. This gives you more flexibility.