TECHNICAL TIP ~ InRoads DTM Conflicts, Part 4
HOW DO I LOCATE A SURFACE PROBLEM?
Now you should have a fair idea about what types of conflicts that you might encounter in a surface model, and some instances on how they got there. The next aspect of this is to locate them, which is just a stepping stone toward eventually getting rid of them. (Or deciding that they pose you no real threat ; )
Just a note - It's at this stage that my documentation of this subject begins to get a bit unstructured and under-developed so don't hesitate to ask me questions if you lose track of what I'm discussing. This is more likely to happen in Part 5 or 6, and quite honestly I can't even believe I'm attempting to document some of this information that has otherwise never seen the light of day.
Moving forward, I'm going to cover these tools in a couple passes. In my first pass, that I'll do in this issue, I will attempt to stay focused on the theoretical functionality of the command and the general nature of how I use it relative to surface conflicts. Later, I'm going to revisit these tools and give you a much greater insight into what is occurring with the command, and precisely how I personally use it. This is where the subject of surface conflicts gets really interesting. (Okay, it's not the DaVinci Code ...but hey ... it's my world ; )
THE THREE MUSKETEERS
There are three tools or commands that are used to locate, diagnose and / or address surface issues in some way. And in my books each of these has its own specific place and usefulness in the grand scheme of surface errors.
And they are:
1) Triangulate Surface, Surface > Triangulate Surface
2) View Crossing Segments, Surface > View Surface > View Crossing Segments
3) Resolve Crossing Segments, Surface > Utilities > Resolve Crossing Segments
Let's take these one by one and briefly describe how I use them.
The primary function of the Triangulate Surface command is to form the relationships amongst the 3D data in the surface and network it all together. And as I've said over and over, you should always stay oriented to the fact that the surface contains two different classifications of information - the 3D data (Features) and the interrelationships (triangulation). This command forms the triangles by relating the 3D data to each other.
But this command can do something else when your InRoads Report Lock is toggled on. (If you are unfamiliar with the InRoads Report Lock then please do us both a favor and buy my book covering all of the InRoads Locks! ; )
On this command there is an option to use Extended Data Checks. It's a toggle switch that is either on or off. Initially when you open this dialog box after launching InRoads, this option isoff. In fact, it's always off ...unless you toggle it on. (Shocking, right?) And notice that this dialog box does not have a Preference button on it, which means that the settings on this dialog box cannot be saved in a 'customized' fashion. Therefore, the settings always open up the same pre-programmed way when you first open the software.
The Extended Data Checks option does some 'extended checks' of the 'data'. (This isn't rocket science.)
And to cut to the chase ... just turn this on and click Apply when you triangulate a surface. When you do, there are a few specialized routines that are run during the triangle formation process. And without getting into further detail about the exact checks that are done (which are beyond the scope of this document)one thing will occur that I always want when first triangulating a surface.
So, when the Extended Data Checks option is toggled on, and the InRoads Report Lock is toggled on, you will be presented with an Error Log. This log is your first insight into the problems or issues that your surface contains. You can save this log, but on my initial triangulation I generally don't bother, especially since this report can be regenerated any time you need to.
This log shows two different types of "errors". One of them, Mismatched Elevations, are the real errors and can cause the most trouble. These are the ones that I focus the most of my efforts on.
The other type of "error" is not really an error in my mind, but more of a "notice" or an "alert". I treat it more like a flag that is pointing out something that I may or may not be aware of. This type of "error" is called an Overlapping Segment.
I'll get more into defining exactly what each of these are a bit later because for now I just want to discuss the three commands that are used to identify any surface issues.
To summarize this so far, I use the Extended Data Checks option on the Triangulate Surface command to form the surface relationships and simultaneously give me a quick insight into any potential issues that the surface might contain. At this stage, my work is done here and I'm ready to move on to one of the other InRoads commands.
Boy, this subject is huge, because I haven't even discussed exactly how the Triangulate Surfacecommand programmatically addresses the issues that it finds. And unfortunately that will have to wait until later, but if you look closely at the Error Log you'll see what's happening with the(Ignored) status next to one of the problem breakline pairs. For now, feel free to let your own intuition take over ... and I'll come back on this and provide more details about this when I get back to it.
From here, now that your surface has been created and you can no longer contain your excitement, you may find yourself viewing contours, or triangles, or what have you. That's fine, but if you have a boatload of errors that showed up in that Error Log then it's only a matter of time before you need to make sure that there aren't any serious problems in your surface model.
View Crossing Segments:
Historically, in earlier versions of InRoads, there were only two Musketeers (the Resolve Crossing Segments tool is fairly new addition) thus making the View Crossing Segmentscommand a vital piece of the error correction puzzle.
This surface viewing command does two things:
1) Places a character of your choosing (usually either an 'X' or an 'O' on the location of a particular type of surface "error" and,
2) Creates the same Error Log report that comes out of the Triangulate Surfacecommand shown earlier.
This command is a good tool to eventually make your way toward in order to get a better glimpse of exactly where the surface issues are on your project. This provides a high altitude look at the issues.
Resolve Crossing Segments:
Before this particular tool was added to InRoads, the challenge was to clearly, locate and identify the specific 3D surface features that were causing the 'errors' and then decide what to do about it. It wasn't that difficult; however the entrance of the Resolve Crossing Segments command definitely improved the overall analysis / correction workflow.
This tool has two modes:
1) Automatic - This method is used to auto-correct any "errors" based on the settings defined within the dialog box.
2) Interactive - This method is used to obtain a list of any "errors" and allow the user to locate them one at a time and address them as they see fit.
Personally, I almost exclusively use the Interactive Mode, but I'm getting ahead of myself.
Okay, I know the information was pretty lean on those last two commands, but I have a good reason for that. ...and besides, I'll be revisiting them very soon in my upcoming second pass.
So, there are three main tools that are used to locate and identify where surface problems exist and each has its place in the grand scheme of things.
Relative to surface errors:
1) Triangulate Surface - This tool is your first notification that errors or issues exist in your surface, and beyond that it forms the triangles by forcing programmatic solutions to any surface hitches.
2) View Crossing Segments - This is a second level tool that provides you with the ability to recreate the Error Log as well as place a symbol in your CAD file so that you can get a high level snapshot of the issues relative to the overall surface and their relationship and proximity to your area of concentration.
3) Resolve Crossing Segments - This is a more recently added tool that provides a higher level of user power to precisely catalog, locate, and address each specific problem in a much more focused way.
I think that's enough for now, don't you?
Next up - ZI Issue 85: Dissecting the "Error Log".