Module 3: Visibility Analysis

Visibility analysis determines what areas are visible to one or more observation points. There are two types of visibility analyses, specifically Line-of-Sight Analysis and Viewshed Analysis. A line of sight is a straight line originating from an observation point to a target point. A line-of sight analysis produces lines that show which parts of the line-of-sight segment are visible from the observation point. On the other hand, viewshed analysis shows the areas of a raster dataset, such as 3D topography data, that are visible to the observer. Two scenarios were introduced: 

1. Line-of-sight analysis and parade route camera placement

A line segment and 3D building scene was used to show what areas of a parade route would be visible from a selected observation point. This analysis shows the best camera locations with the best viewing angles, but this type of analysis can also be applied to security/surveillance scenarios or many other applications. 

2. Viewshed analysis and campground light illumination placement

A viewshed analysis indicated the areas that are illuminated by installed lamp posts in a campground. The goal was to have the majority of the campground illuminated by at least 2 light sources, shown as orange in the screenshot below. The final results were obtained after utilizing the Viewshed tool and the Raster Functions Greater Than tool, which determined the number of overlapping visible areas. After seeing the results, decisions can be made to increase the light coverage, such as increasing the number or height of the lamp posts. 

Additionally, this module focused on the basics of using and representing 3D data in ArcGIS Pro. 2D data with z values can be shown in a local scene (smaller areas and small datasets) or a global scene (curvature of the Earth is relevant, large datasets). Key tips include doing a cartographic offset for objects, which involves offsetting objects an equal measurement in order to see points above a 3D surface more clearly, such as the points seen below: 

The z value does not always have to represent elevation. The scene below extrudes the parcel boundary based on the parcel's estimated value, in which the tallest parcels had the highest values. 

My favorite part of this module was creating a realistic 3D scene, complete with realistic trees, grassy areas symbolized with procedural fill technique, buildings symbolized with rule packages, and even  animated water with moving ripples. 

If the scene is a global scene, additional modifications can include creating shadows based on a specific date and time and various weather conditions. For example, see the link below for a 3D scene of buildings in Portland where the time is set to July 15, 2021 at 4:00pm CT with animated rainy conditions. 

https://pns.maps.arcgis.com/home/item.html?id=b9b56700a36042798d7cf7b5b5010ade 

3D data representation has so many applications to create more realistic scenes that can be explored and create more eye catching visual graphics. I look forward to applying these new skills to future graphics!