Author Archives → Marcia Moreno-Báez

Research Professor in Geospatial Technology, The Fletcher School, Tufts University. 🌏 Geospatial Technology and Data Visualization Enthusiast

Stack, Clip, Intersect! How GIS Overlay Analysis Turns Maps into Answers

The Power of Overlay: Making Maps Think for You

Maps are great at showing us where things are, but GIS goes a step further by helping us understand how things relate to each other spatially. One of the most powerful ways GIS does this is through overlay analysis, a technique that works with both vector and raster data to turn layers into insights.

Think of overlay analysis as asking your map to think logically: What overlaps? What’s inside what? Where do multiple conditions occur at the same time?

Overlay analysis combines multiple spatial datasets by stacking them on top of one another and analyzing their relationships. The result is a new layer that contains information from all the inputs — geometry and attributes.

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Seeing the Patterns: How Spatial Analysis Reveals Hidden Stories in Conflict Zones

Have you ever wondered why certain types of conflict seem to cluster in specific regions — or why some areas remain peaceful?

Timelapse of conflict hotspots in Ukraine for three month periods from February 2022 to April 2024. Julia Huber. From Escalation to Exodus: Mapping the Evolution and Human Toll of the Russia-Ukraine War

Traditional analysis might count how many incidents occur. Spatial analysis lets us see how those incidents are arranged — are they clustered around borders, along roads, or near population centers?

For example, in a conflict zone, we might find that attacks cluster along major highways or near disputed boundaries. This pattern tells us something about accessibility, control, or strategic importance — insights that are invisible in non-spatial data.

Here is where spatial analysis plays a huge role.

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Preparing Excel Tables for ArcGIS Pro

Best Practices to Import Data for GIS

Working with GIS often starts with good data—and for many of us, that means working with Excel tables. Before importing your spreadsheets into ArcGIS Pro, it’s important to clean and format them properly. A little preparation upfront can save you a lot of time (and errors) later on.

To make this easier, I’ve created a series of short tutorial videos that walk you through some of the most useful tips and tricks for cleaning Excel files before bringing them into ArcGIS Pro. But first, let me walk you through a couple of points on why it is important.

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The Fundamentals of Coordinate Systems

Coordinate systems and map projections are super important because they help us accurately represent locations on Earth, align data from different sources, and minimize distortions when we create flat maps from a round planet. Without a consistent coordinate system, like latitude and longitude, we wouldn’t be able to pinpoint locations or analyze spatial data properly. Projections help us handle the tricky task of flattening the Earth by letting us control how things like shape, distance, and direction are distorted. This is key for everything from navigating and measuring distances to creating visually accurate maps. In short, they ensure that our maps and data make sense and work correctly across different applications.

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The Hidden Bias in Maps

Learning the Modifiable Spatial Unit Problem (MAUP)

Have you ever noticed how the way we draw boundaries on a map can totally change the story the data tells? Think about it: if we look at average income by State, we might see big differences county by county… But if we zoom in and look at income by tract, the data will tell us something different! Same data, different story.

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Introduction to GIS Data: Choosing, Understanding, and Using It Responsibly

Choosing the Right Layers in GIS

When you’re first exploring a data portal, it can be tempting to download and add every layer you see. After all, more data feels like more power, right? But in GIS, adding too much information can quickly lead to cluttered maps, longer processing times, and even misleading results.

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Cartographic Principles, Classification and Symbology

Cartography is the art and science of making maps, and in the context of geographic information systems (GIS) it is a critical step in turning data into information people can actually use. Maps are not just pictures of geography—they are carefully designed tools that help us navigate, see patterns, understand relationships, and share knowledge about the world around us.

A map’s effectiveness comes not only from the data behind it, but also from how its elements are designed and organized. Titles, legends, scale bars, symbols, and the map body all play a role in communication—but whether they succeed depends on applying solid cartographic principles.

In this post, we’ll first walk through six of the most important cartographic principles that every mapmaker (and GIS user) should consider when designing a map. We’ll then move into classification methods and symbology, which are essential for turning data into clear and meaningful visual stories.

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