Property Alterations: Get Elevations from Layer Names

Map 3D Projection Rounding – It’s Just Cosmetic

Last week, I was attending Arizona Professional Land Surveyors Annual Conference, Tom Homan, a GIS Coordinator for Gila County did a great workshop on working with AutoCAD Map. While he was preparing for his presentation, he was working with AutoCAD Map 2012, and ran across a potential problem. He found what looks like a problem with the coordinate projection used in the Arizona State Plane projections. While looking at the details for the projections, he noticed the Scale Factor was showing a 1.000000 rather than the expected 0.9999. That may not sound like much, but that’s 1 in 10,000 units, or a foot across a little less than two miles. This is a pretty big difference across a large are, such as an Arizona County (the counties in AZ are typically larger than those of most states). Now, Gila County, AZ is a mountainous area with a lot of vertical change which can really cause havoc with projections.  To deal with this, they use some custom Low Distortion Projections. He also found a similar problem when creating these custom projections. After saving, the projection file was rounding up to 1.000000 as well.

So after digging a little bit, and reviewing the projection definition dictionary, the correct scale factor was built into the files. I also created some data, did some reprojections, and exported out to a shape file to see how the projection file (PRJ) turned out, and sure enough, it was creating the correct scale factor. It looked like it was a cosmetic issue with the dialog box form. So, after creating a support case with Autodesk, Nathan Moore validated the issue as a form display parameter rather than a functional problem with the dictionaries. The issue is also present in Civil 3D 2012.
So, the good news is the projection tools in Map 3D still work great, and with the new tools much easier to work with.

Time for an advantage…

Autodesk has released the new Subscription Advantage Packs for the 2011 products. These Packs give some additional tools to the software users and provide a little extra value to those users on subscription. Last year, we got cloud file capability with AutoCAD Map 3D.  The Packs are downloadable fromt he Scubscription Center, and are now available.

In addition to the added AutoCAD tools which my coworker Isaac Harper blogs about, one of the tools I’m looking forward to most is the new FDO providers. There is a new FDO Provider for ArcGIS allows direct, editable connections to Personal and File Geodatabases as well as SDE connections. These data stores are becoming increasingly popular, particularly as portable GIS data stores. The new FDO Provider opens up more possibilities for managing spatial data without conversion right inside AutoCAD Map 3D (or Civil 3D as well).

Getting Your Results – Using Network Topologies

One of the important tools that AutoCAD Map 3D includes is the capability to work with topologies. It can create and manage them, and more importantly, do analysis from these topologies. Basic training classes, and all of the books I’ve seen, show how to create, manage and perform analysis with topologies.  One thing that is absent, is how to take advantage of and access the results after the analysis – it’s the cause of a lot of questions from people I work with.

Before I get on to working with the results, I want to give some background of topologies, and how AutoCAD Map 3D manages them.

Topology is a technique for managing spatial relationships between objects. It is a particularly useful technique for managing networks of objects, such as utilities or streets. The relationships allow you to trace up- or downstream to answer questions, such as:

• What customers will be out of power if this line is down?
• What is the likely source of contaminant (common point upstream) when there are a series of sites that are showing high levels of contaminants?
• What is the shortest route between two locations?

The relationships are created by maintaining unique identifiers for each point or junction and line in data tables. These identifiers are called Primary Keys. The lines will also contain fields to include the identifiers of the points from each end of the line. These are called Foreign Keys. By searching for lines that have a specific point identifier, you can find all the lines that connect to a point, and go from point to associate line to associated point to associated line, etc, much like a monkey swinging from one vine to the next.

Consider the example below.  Here is a collection of lines and points. There is graphic representation of the network, and a snapshot of the data tables from the network. Look at point # 2364.  It appears to be the end of

that particular network stream. We look for all of the lines that have either a start point or end point value equal to 2364, and we find that line # 6888 has 2364 as an end point. We then look at the other point value and find it is 2359 (the start point and end point allow a topology to show direction as well as just connections), so we search the line table for other lines that have that value. We will find line #’s 6887 and 6921. We can then continue in this process until we get the results we are looking for.  For a best route, we will evaluate the potential sets of lines that provide a connection between the two points, and use some criteria to determine the best (usually the shortest lengths) set or route.

AutoCAD Map 3D provides tools and the data structures to create and manage topologies, as well as topology analysis tools. Within the Task-based Workspace, the topology commands can be found on the Object Map ribbon on the Topology panel.   The only thing required to create a network topology is a clean network of lines (clean means that the end of one line exactly meets another line – their coordinates should match). Map 3D will create points (called Nodes) at the junction points if they don’t exist in the data.

Once a network topology is created, Map 3D will create Object Data to manage to topological relationships. The nodes will get a table called TPMNODE_topologyname (where topologyname is the name of the topology). You can use the Edit Object Data command (The Object Data panel of the Object Map ribbon) to select a node and review the table information. The ID field is the critical element (the resistance values can be used to manipulate the analysis – for example, the resistance on a point could be a time factor for an average stop at a stop sign so route can be qualitatively compared including stops, turns, etc).

You can also see the values of the object data by selecting an object and reviewing the Properties (on newer versions of map 3D).

The lines (Map 3D calls them LINKS) will get their own set of Object Data, called TPMLINK_topologyname. The line (or link) object data will include additional fields. The critical elements are the Start_Node and End_Node fields, which are how Map 3D manages the topology relationships.

The purpose of creating and managing topology is to perform analysis, and the tools are also available on the Topology panel of the Object Map ribbon.  The three network analysis tools are Shortest Path, Best Route and Flood Trace.

When completing the analysis, you have the option of highlighting the results with a color (it will go away with the next redraw), or save to a topology. You will give the results a name (my example attached was a flood trace, and I named the resulting topology FloodResults).

Once the topology is created, I can always re-highlight the topology, but it goes away with each redraw. That makes it a bit difficult to use for further analysis or to even print the results.

The easy way to work with them at this point is to save the drawing with the result topology (or topologies) and open a new drawing. In the new drawing, use the Map 3D drawing attach tools to connect to the results drawing.

In the Map Explorer of the Task Pane, the topologies from the attached drawing will be visible in a greyed out icon. This means the topology hasn’t been loaded into the current drawing.

Right-click on the result topology and select the Load Topology option under the Administration menu.

This will open a dialog box with the option to Create objects when loaded. Selecting this will recreate the topology objects in the current drawing, essentially making a copy of the topology data from the original file.

You may have to Zoom Extents to see the newly created data.

At this point, we now have just the objects and topology from the result topology we created. We can save this and have it available for future applications and uses, such as printing route maps or performing buffers, etc. In addition, the objects will have not only the object data from the results topology, but it will also have the data from the original topology and any object data from the original objects.

Try Out a Map Book

On the Task Pane of AutoCAD Map 3D, there is a series of tabs. I spend a lot of time demonstrating and talking about the first two, but I don’t spend much time on the third one – Map Book. The Map Book tab is simply a set of tools designed to help users generate an easily reproducible set of printed maps. It will generate a standard AutoCAD Sheet Set, but will include some tools specifically designed to simplify setting up a grid-based Sheet Set, complete with a key map and navigation features.

You can also have a number of Map Books defined. You may want different books for different utilities, or you may have different scales needed for different map sets. Moving back and forth is just a matter of selecting the appropriate map book at the top of the task pane.

Before creating a new map set, you need to make some decisions. You will need a template drawing file with a layout defined with a title block, and if desired, the adjacent navigation blocks, main, key view and legend viewports. There are a number of templates to use as examples that come with Map. You can find them with the other templates in \Documents and Settings\\Local Settings\Application Data\Autodesk\ AutoCAD Map 3D 2010\R17.2\enu\Templates. These templates may net perfectly suit your specific application, but they can give you some ideas.

You can open one of these and use the Identify Template Placeholders command from the Tools button to look through the settings.

Once you have everything ready, you can use the New button to start a new map book. As with most things Map, you will get a workflow-based dialog box. Go through each section of the dialog before closing the dialog or hitting the generate button.

First, you’ll set a name in the Source. You will select Map Display if you’re plotting objects from the Display Manager (primarily FDO connections) and Model Space if you’re selecting AutoCAD Objects. Remember, you can add Objects from model space into the map display.

Your next step is to select the template drawing file, with the Layout and Title Block you’ve setup. At this point you can add the links to adjacent sheets. You will also set the scale here.

Next, you will set up your map grid using a Tiling Scheme. You can set the grid based on the size of the map (area), by the number of sheets you want, or by selecting a premade grid made from existing closed polylines. You can also set a map overlap, so that you can have a strip of surrounding area. You do that with a percentage.

If you want to create an overlap, and still keep scale maps (I’m not sure who wouldn’t), a friend of mine, Jeremiah McKnelly wrote a great tip for getting true scale map books with an overlap. Check it out here.

The next step is to set a naming scheme for your grid. You have several options based on numbers, letters, or you can even use data from the drawing using the expression builder.

Next you can define your key drawing. You can use premade keys, or generate one on the fly by selecting the layers you want to show.

You can then add a legend where map will setup the viewport if you’ve already created a legend, or you can set up a space to add one later.

Finally, you get to define where you’ll put your sheet set definition file (.DST).

After all this, your Map Book tab will now display all the sheets with their views. You can check the properties of one of the views to see the adhacent sheet information stored. You will also see all of your new layouts, all named and ready to go.

The process allows you to very quickly layout some simple sheet sets with very minimal effort. If your organization needs to plot map books or sets of printed maps, this may be the right tool for

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