Curved lines turn to straight lines after sDNA preparation

Curves Gone Straight: Decoding sDNA’s Network Prep Quirks

Ever wrestled with spatial network analysis and watched your carefully drawn curves morph into rigid straight lines? If you’re using Spatial Design Network Analysis (sDNA), you’re not alone. Architects and planners importing data from CAD programs like AutoCAD often hit this snag. It’s a classic case of data prep gone a little sideways, and it all boils down to how sDNA handles curves.

sDNA, for those unfamiliar, is a seriously powerful tool. It’s designed to dissect spatial networks – think streets, paths, and urban layouts. Planners and designers use it for everything from predicting foot traffic to figuring out how the built environment impacts our lives. Unlike some tools that chop curves into a bunch of tiny straight segments, sDNA can treat them as single, smooth units. This can be a huge time-saver, especially when you’re dealing with dense, complex road networks.

So, where does the straight-line transformation come in? Usually, it happens during the network preparation stage – that crucial step where you’re cleaning, connecting, and generally getting your data ready for analysis. The culprit? It’s often a clash between your input file (like a DWG from AutoCAD) and the XY Tolerance settings lurking within your geodatabase (GDB).

Think of it this way: DWG files and XY Tolerance don’t always play nice together. XY Tolerance is basically a rule that sets the minimum distance between points in your network. If points on a curve are closer than this tolerance, the software says, “Eh, close enough,” and merges them. Import a DWG into a GDB with a too-tight XY Tolerance, and those closely spaced points on your curves get collapsed. Poof! Curve gone, straight line in its place.

How do you dodge this bullet? Simple: manage your XY Tolerance. After importing your data into the GDB, peek at the feature class’s projection properties and tweak that tolerance setting. A default of 0.01 meters often works, but the sweet spot depends on your data and how precise you need to be. Just make sure the tolerance is bigger than the distance between those curve-defining points.

But hey, XY Tolerance is just one piece of the puzzle. Network prep is a holistic thing! You also need to make sure everything’s properly connected, fix those near-misses where lines almost touch but not quite, and double-check your data’s spatial reference system. sDNA has tools to help you sniff out and fix these issues, keeping your network data squeaky clean.

Bottom line? Curves turning into straight lines during sDNA prep can be a real headache, but understanding the XY Tolerance gremlin is half the battle. Tame that setting, pay attention to the other prep steps, and you’ll ensure your sDNA analysis actually reflects the real-world complexities of your spatial networks. Trust me, that extra bit of care is worth it when you’re trying to make informed decisions about our cities and infrastructure.