Creating minumum polygon coverage from set of lines in ArcGIS Desktop?

Turning Lines into Shapes: Creating Polygons from Lines in ArcGIS Desktop

Ever needed to turn a bunch of lines on a map into actual shapes? It’s a pretty common task in the GIS world. Whether you’re mapping out property lines to create parcels, tracing shorelines to define lakes, or even zoning areas based on roads, ArcGIS Desktop has got your back. Let’s walk through how to create those polygons from a set of lines, and how to do it right.

Why Bother with Polygons Anyway?

Lines are great for showing linear stuff, but sometimes you need a closed area – a polygon. Polygons let you do all sorts of cool things, like calculate the area of a forest, measure the perimeter of a park, or just generally represent something as a defined space. The goal here is to create polygons that hug those lines as closely as possible, without weird overlaps or gaps. Think of it like shrink-wrapping your lines!

Getting Your Ducks in a Row: Preparing Your Data

Before we jump in, a little prep work goes a long way. Think of it like getting your ingredients ready before you start cooking.

• Close the Loop! This is crucial. Your lines have to form closed shapes if you want a valid polygon. Any little breaks or unclosed lines, and you’ll end up with incomplete polygons. Use the editing tools in ArcGIS to connect those lines and close any gaps. The snapping tool is your best friend here – it’s like a magnet for vertices!
• Tidy Up: Get rid of any duplicate lines or segments that are sitting on top of each other. These can cause all sorts of headaches during the conversion process. The “Planarize Lines” tool is great for splitting lines where they intersect, ensuring everything’s nice and clean.
• Attribute Check: What do you want to do with the information attached to your original lines? Do you want to keep it, ditch it, or combine it somehow in the new polygons? Decide this upfront.

Let’s Make Some Polygons: The Conversion Methods

ArcGIS Desktop offers a few ways to turn those lines into polygons. Each method has its own strengths and weaknesses, so let’s take a look.

1. The “Feature To Polygon” Tool: The Workhorse

This tool, found in the Data Management toolbox, is a solid, all-around option. It’s like the reliable family car of polygon creation.

How to Use It:

2. “Construct Polygons”: The Interactive Approach

If you have ArcGIS Desktop Standard or Advanced, the “Construct Polygons” command on the Advanced Editing toolbar is pretty slick. It lets you create polygons interactively in ArcMap.

Here’s How:

3. Editor Toolbar Tricks (Basic License): The DIY Method

Even with just a Basic license, you can still get the job done with a little creativity.

The Steps:

4. “Minimum Bounding Geometry”: The Simplifier

This tool doesn’t directly convert lines to polygons, but it can create polygons that represent the smallest area that encloses your lines. Think of it like drawing a box around your lines. It’s handy when you need a simplified polygon shape.

How It Works:

Watch Out For These Gotchas!

• Gaps and Overlaps, Again: Seriously, these are the bane of polygon creation. Double-check your lines!
• Sliver Polygons: Sometimes you get these tiny, skinny polygons that are more trouble than they’re worth. The “Eliminate” tool can help get rid of them, or you can just manually edit them out.
• Dangling Lines: Lines that don’t connect to anything are a no-no. Either connect them or delete them.
• Self-Intersecting Lines: Lines that cross themselves will cause the “Feature to Polygon” tool to throw a fit. Fix them!

A Word About ArcGIS Pro

While we’ve been talking about ArcGIS Desktop, it’s worth remembering that Desktop is on its way out (retirement is planned for March 1, 2026). Esri is pushing everyone towards ArcGIS Pro. The good news is that most of these techniques work in Pro too, although the interface might look a little different.

Wrapping Up

Turning lines into polygons in ArcGIS Desktop is a fundamental GIS skill. By prepping your data carefully, picking the right tool, and keeping an eye out for potential problems, you can create accurate and useful polygons for all sorts of projects. And remember, ArcGIS Pro is the future, so start thinking about making the switch!