Thursday, April 2, 2015

3D Mapping

This week in, GIS3015, Cartographic Skills, we worked on 3D Mapping; the Pros and Cons. The lecture objectives were as follows:  

- Describe 3D data types and associated applications
- Recall different types of 3D Maps
- Describe the challenges and advantages of 3D Mapping
- Recall how to manipulate 3D data in ArcScene

And, for the Lab:

- List and Describe data necessary for 3D GIS
- Perform techniques to visualize raster data in 3D
- Perform techniques to visualize feature data in 3D
- Convert 2D feature to 3D using elevation values derived from lidar data
- Demonstrate proficiency with 3D Analyst Extension and ArcScene
- Export data to kmz and view in Google Earth
- Describe applications of 3D data
- Compare and contrast a complex flow map in 2 vs 3D

So, where to begin??? 

There were a number of tools and reference material that we covered including the below:

Using Google Earth was fun and quite practical, as anyone with a computer and internet access can use this 3D tool. The other tools were equally useful and fairly straight forward to understand.  The tool to convert a layer to a KML (KMZ) file was also quite useful. I created the file: Ex2BostonBldgsKML. 

The best part of creating this file was watching the globe spin, very slowly, and eventually zoom to the location I had created; I wasn't sure my computer would survive.

Another tool I learned how to use was the, Extrude capability in ArcScene. Below is a snip of the file I worked with. 

All of this was brilliant, but the most important aspect of 3D Mapping I learned was in regards to, vertical exaggeration, illumination, and background color.  Above I discussed vertical exaggeration, so here I want to spend a brief time on illumination.

The default Sun elevation is set to 30 degrees above the horizon with the default compass direction of 315 degrees which puts the Sun in the Northwest. To minimize the shadows on my map I could place the Sun at an elevation of 90 degrees along a West to East line (270 degrees to 90 degrees). This would place the Sun directly overhead. In the image below, I moved the sun around Santa Barbara Island and could see how the shadows changed around the cliffs and over the land rolling to the water's edge.

At the end of the day, we must decide whether or not to use 3D feature techniques in our work. There are clear advantages to using 3D layers: 3D layers make it possible to answer questions one cannot address with a 2D map. For instance, you can address questions such as: On what floor of a high-rise condominium is it best for rescue/first responders to ingress? What vantage point should a sniper take in order to defeat a would-be threat in a large urban area where buildings, trees and other objects might obscure a clean shot? What is the best route to take to remain in the shadows given a certain urban design and time of day? There are countless military and civilian applications well suited for a 3D building layer.

On the negative side or Cons to using 3D layers: You must have a computer to view the 3D effects. If you want something that is easily transported, a paper map is better. There is also a possibility that a user may not fully comprehend what the cartographer is trying to represent in a 3D map and this might cause more confusion instead providing clarity.

However, I believe the Pros far outweigh the Cons when it comes to making a decision to use 3D mapping techniques.  Of course, we should only use these 3D techniques where and when they are appropriate; to enhance your map or emphasize a particular message.

No comments:

Post a Comment