Being Civil

Why Do I See Difference in Time Series Plot And Output Results / Analysis Summary?

A lot of times, SSA users find that there is a slight difference in the results seen in the Time Series Plots and the numbers seen within the Analysis Summary in the elements Property dialog as shown below:

Figure 1.0 Different results seen in the Time Series Plot and Analysis Summary

The Time Steps section within the Analysis Options is the key to resolve this difference seen in the results. It establishes the time step length to be used for the runoff computations, routing computations, and results reporting. The Reporting and Routing Time Step is the most important thing for network analysis.

SSA uses a default Reporting time step of 5 minutes and Routing time step of 30 seconds. In most cases users tend to use the default and define only the Start and End Dates to perform the analysis. A very important thing to note here is that the Output Report or Analysis Summary within the element properties windows shows the results based on every routing time step whereas the Time Series Plot is generated on the Reporting time steps defined. This is where the difference emanates.

Lengthening Time Step

I'm Anurag Thakur. I am a Science graduate who started my Civil Engineering career in 2007 by joining BOSS international as an application Engineer. In BOSS International, since 2007, I supported their Hydrology and Hydraulic software, StormNET; now called as Autodesk Storm and Sanitary Analysis and RiverCAD Pro. Later in 2010, I joined Autodesk, Inc as a consultant for Autodesk products (Storm and Sanitary Analysis and RiverCAD Pro) and on April 01, 2011 joined Autodesk, Inc as a Product Support Specialist.

Now, the topics related to Autodesk Storm and Sanitary Analysis (SSA) will be available under the Hydrology link on the top of the page, as mentioned by my colleague Matt in the Blog introduction to Autodesk Storm and Sanitary Analysis. I will start with post, Lengthening Time Step.

I have seen it number of times where the model goes crazy when being modeled with the hydrodynamic routing and we start having doubts about hydrodynamic wave calculations. Specially it happens for a model, in which the conveyance links length may vary too much .  However, under such circumstances, the rule of the thumb is to set up a lengthening time step. Details on Lengthening time step are available in SSA user guide. This is a time step, in seconds, used to artificially lengthen channel and pipe links so they meet the current stability criteria under full-flow conditions. It means the travel time of a wave will not be smaller than the specified conduit lengthening step. With the decrease in the value, fewer channel and pipe links will require lengthening. A zero value for Lengthening time step means that no channel and pipe links will be lengthened (i.e., will be using their defined length values). However the insuitability of the results could be reflected in the Analysis results, and in the Time Series Plots.

  

 
 

If the model appears to be unstable then increasing this value will tend to make the model more stable. Most of the time, while troubleshooting such issues, setting up the lengthening time step resolved the hydrodynamic wave calcs. The user could try using a value of 60 secs and check if the model results become more stable.  If the model results are stable, try reducing this value to the minimum possible while keeping the model stable. On the other hand, if the model results are not stable, then continue to this value up to a maximum of 300 (5 minutes). If the mode is not stable at this increased value, then there is something else causing the model instability.

I hope you find this useful, "Enjoy your hydrology, stay tuned for more".

 

New Things to Being Civil Blog

If you are reading this post you may have already noticed few things different to this Blog. With growing popularity of social media such as Facebook and Twitter, as well as our world wide presence we decided to add few cool features to help the message get out there quicker and stronger.

 

On the top right you may see a Google Translate bar. All of our non-English speakers may appreciate this tool. Please look at Google Translate as a work in progress tool. Some languages or articles are spot on, while others are not so much. The tool is getting better every day and maybe in the future will be good enough to do an error proof translation. But, until then use it to get the sense and better understanding of the topic we are are covering in the post.

Right below the post you may now see a star rating for the post. This way you can give us your instant feedback. With this tool we will be able to report the topics of your interest and learn from it. Off course, the more popular subject and rating is the more similar areas we will try to cover. Other way to look at it is to virtually “tip your server”. If you are happy with what you are getting please tell us so.

Slightly below the Star rating widget, there is another tool that basically link the post to a similar previous posts. I have to admit, I am not sure how the linkage is being determined, but suspect there is some smart gremlin running inside, reading the post and deciding what links to what. If you have better explanation please share it with us.

Even further down, there are few buttons which allow you to tweet (Twitter) the post or Like (Facebook) the post. If you like it or you think it’s worth sharing, then don’t be shy. Just click it!

Unlike other “Like” under post, the Like at the left side is used if you like Being Civil Blog Facebook page. Yes, we do have Facebook page! Please use these addition and help us spread the word. Help us get the cool tips and ideas get further than our closed community. Evangelize and educate!

 

 

Join Us In Welcoming Another Autodesk Civil 3D Blog!

Please join us in welcoming Isaac Rodriguez, Senior Software Engineer to the Autodesk Blogosphere! Isaac is the author of Civilized Development, a blog dedicated to the AutoCAD Civil 3D API.

For those of you who are not familiar with Isaac, here is his bio from the blog:

Isaac Rodriguez is a Sr. Software Engineer in the AutoCAD® Civil 3D® team. He has been with Autodesk since 2001 working in different products and technologies, and currently, he is the Software Development Lead of the AutoCAD® Civil 3D® API. He has several years of software development experience ranging a broad set of technologies and programming languages, and for the past few years, his work has been related to .NET.

When he is not writing code for Autodesk or taking care of this blog, you can find him playing blues with his band, shutting pictures, or enjoying a good book. As an former members of the SEI (Sociedad Española de Ilusionismo), he has a special interest about magic and loves to read about the subject.

 

If you are a developer interested in creating your own AutoCAD Civil 3D extensions, Civilized Development is definitely the place to start. Be sure to read Isaac’s first post for more information about his endeavor!

Check out Autodesk Homestyler

Ok, Ok – it’s not Civil 3D, but if you haven’t checked out the newest version of Autodesk Homestyler, you have to take some time and do so. There are great new features, including the ability to create high-res Snapshots to get a realistic view of your new home design.

We used this right before we moved, and it made buying and organizing furniture so much easier!

Give it a try: http://autode.sk/eRl6bz

Question for our Twitter followers

Currently, we have all new Knowledge Base articles related to Civil 3D pushing through to our Twitter Stream.

Do you find these helpful or just added noise?  Please leave a comment and let me know what you think.

Thanks!

UPDATE:  For those looking to add the KB feed to their RSS Reader, here is the link I posted last month:  http://rss-support.autodesk.com/rss?f=5dacde90-01de-11de-2eb3-0019bbc55f7f

Or you can create your own custom feed here: http://rss-support.autodesk.com/subscription

"Don't forget your AutoCAD roots" - thanks Jack!

Hey all, today I wanted to highlight a simple tip provided by none other than "Junction Jack" our Autodesk Technical Consultant based in the United Kingdom.  His blog, co-authored with Ove Cervin, another Technical Consultant based in Sweden, is also great Civil 3D reference for you to keep track of (and is on our sidebar on the right).  

In general he is mentioning a simple but powerful tool on the snap menu that you may have overlooked (I know I didn't pay attention to this one!):

Check out his post for the full description, including a YouTube video.  Jack - the only problem I have with the included YouTube video, is that we don't get to hear you speaking the "other" English!

Check out his post for the full description, including a YouTube video.  Jack - the only problem I have with the included YouTube video, is that we don't get to hear you speaking the "other" English!

Using Process Monitor for Troubleshooting

Some of the more difficult cases to solve are the ones that are caused by a conflict with another application, or a rogue permission issue.  These are typically computer-specific, or perhaps specific to one’s network environment.  Two of Microsoft’s gurus (Mark Russinovich & Bryce Cogswell) have released a utility called Process Monitor.  This is a real-time visual of what is going on with your machine, and is a great tool to help troubleshoot these issues.