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.
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:
- Z (height)
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
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.
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.