July 25, 2023

What’s that Mountain Over There? A Guide to Mobile Line of Sight and Visibility Analysis

Written by: Emily Hunt & Amanda Lind

Have you ever looked across a landscape and wondered, ‘What mountain is that?’ or ‘Which island is that just beyond the bay?’ That’s where viewshed analysis comes in. With the Viewshed tool in Global Mapper Mobile Pro, the answer is in your pocket. Instead of guessing with Google Maps or trying to eyeball elevations, Global Mapper Mobile can instantly highlight all visible areas from a vantage point. Just stream or load an elevation layer, tap the Viewshed tool, and see exactly what’s in view.

What are the names of these peaks near Grafton Notch State Park in Maine? Let’s find out!

What is Global Mapper Mobile Pro?

Global Mapper Mobile Pro is a powerful, yet user-friendly app for capturing and creating GIS data in the field on iOS and Android devices. It works with your device’s built-in GPS or connects to high-accuracy Bluetooth GNSS receivers to deliver precise positioning, situational awareness, and locational intelligence for remote mapping projects. Designed as the perfect companion to the desktop version of Global Mapper, the mobile edition puts maps in your hand. Its ideal for engineers, surveyors, foresters, emergency response teams, and anyone who needs reliable access to spatial data in the field.

The Visibility Analysis Toolkit

So what do you need to perform a viewshed analysis? Here’s a quick checklist of essentials to have on your mobile device:

Global Mapper Mobile Pro – The Pro version of the application is required to access the Viewshed tool. This yearly subscription can be purchased on our website or the Apple App Store (iOS).
Elevation Layer* – A raster layer that represents terrain elevation. This is the core data the Viewshed tool analyzes. (Bonus tip for fellow GIS enthusiasts: you can include trees, buildings, and other structures by creating a digital surface model (DSM) from lidar data in Global Mapper Desktop. Using the Max Binning method a layer representing the tops of trees will be generated—just remember to include the ground elevation at your standing height!)
Topo Map* – Recommended as a reference layer to display the names of mountains, hills, islands, and other landscape features. Learn how to create your own topographic map in Global Mapper.

*This data can be streamed directly to your device using the Online Data tool (if you have service) or downloaded as a package file from your Global Mapper Desktop. For a step-by-step guide on preparing and transferring data, see our blog on Data Sharing between Global Mapper Desktop and Global Mapper Mobile.

Control center layers — In the Control Center, elevation and topo map layers are loaded

How to Use the Viewshed Tool

How does it work? The viewshed tool analyzes your position and generates a new layer that highlights every location visible from a chosen point –whether that is your current location or a point feature you’ve created on the map. (If you’re in the field, ensure that your location services are turned on!)

Once your data layers are loaded, open the Toolbox in the lower left corner and select Viewshed. Most default settings will work just fine, but adjusting a few key parameters can help refine your results to the specific area.

Here are the settings we recommend customizing:

Radius – Defines how far the tool should look. You can estimate the distance between you and the mountain or use the Measure tool found in the same menu for better accuracy.
Transmitter Height – The height above ground from which visibility is calculated. For a person standing on the ground, set this to around 2 meters (or adjust if you’re on a tower, building, or other structure).

For more details on other parameters, check out the full tool specifications in the Knowledge Base for iOS or Android.

Viewshed Analysis

Once run, the Viewshed tool will create a pink vector feature highlighting all the areas visible from your chosen location. Once the analysis is complete, you can save the results directly to your device for future reference or export them to Global Mapper (desktop) for further visualization and analysis.

completed viewshed displayed highlighting areas visible in the first image — The viewshed highlights the mountains and valleys visible from the selected point with a pink outline, or area feature.

Viewshed over a topo map allowing landscape names to be visible — From the result, we can see that the tallest mountain in the distance, in the center of the image shown earlier, is called Old Speck.

Terrain Visualization

iOS users can bring this viewshed to life with the 3D viewer in Global Mapper Mobile. This feature allows for interactive 3D terrain visualization, letting you explore your landscape analysis from every angle right in the palm of your hand. Whether you’re working with a point cloud, digital surface model (DSM), or contour layer, the 3D Viewer provides a powerful way to enhance mobile GIS projects and better understand terrain features in the field.

The Viewshed tool makes it easy to answer the classic line-of-sight question: What can I see from here? It provides quick and reliable remote visibility analysis—whether you’re planning a hike, siting a tower, or simply curious about the landscape around you.

Viewshed analysis is just one of the many advanced capabilities included in Global Mapper Mobile Pro. Ready to try it out? Download the free base version of the Global Mapper Mobile app from the iOS App Store or Google Play Store, and explore how it can put powerful mobile GIS tools right in your pocket.