April 2, 2012

A Point Cloud Is A Point Cloud... Or Is It?

In today’s blog post, Ideate’s Application Specialist Matt Miyamoto discusses the differences between a Point Cloud created with the POINTCLOUD command and an AutoCAD Civil 3D Point Cloud object.

I recently had the opportunity to do a Lidar presentation at the Land Surveyor’s Association of Washington (LSAW) Conference at the Tulalip Resort a few weeks ago. During the presentation, the attendees and I had a great discussion on a few of the different laser scanners out there on the market and I was able to get some great feedback on their opinions of each.

The main scanners in use appear to be from Trimble, Leica, Faro and Topcon.  Different scanners may use different methods for data collection and also may come with different tools for processing, reviewing and editing the raw data from the scanner. Most of the users appear to be using Trimble and Leica scanners along the Point Cloud related software that is available from each manufacturer. Trimble has Trimble Link and Trimble RealWorks software, and Leica has CloudWorx and Cyclone that can be used for quickly reviewing and processing data. FARO scanners were also mentioned based on the speed of scanning, which produces large amounts of data in shorter time.

The discussion on different manufacturers also brought up a very important point. A Point Cloud in Civil 3D is not the same as a Point Cloud in AutoCAD. Civil 3D Point Cloud objects include different properties and capabilities that are tied in to the Civil 3D application. The ability to control its display using Styles, and add Points to a Surface only appears if the Point Cloud is a Civil 3D object rather than plain Point Cloud object. There are also two different commands used to create each in a drawing file.

The POINTCLOUD command is a base AutoCAD command that allows users to Attach, Index, control the Density or Lock a Point Cloud in the drawing file. Due to the limited Attach or Index options, only a handful of file types are available (.PCG and .ISD for Attaching and .LAS, .XYB, .FLS, and .FWS for Indexing).  Civil 3D uses a different processing engine with its Create Point Cloud command, so a raw data file can be processed into an external .ISD database file that Civil 3D will use for the Point Cloud’s definition. Because of this process, a larger variety of file formats can be used, including GIS data, existing database information, pre-defined manufacturer specific formats, and plain text format files.

With Trimble, Leica and Topcon, the manufacturer specific file formats are part of the default file type list available in Civil 3D. These files can be selected directly when used with the Create Point Cloud command. 
For FARO scan files, the .FWS and .FLS format files must first be indexed using the POINTCLOUD command, and then converted to a Civil 3D Point Cloud object. Although this is an extra step, Civil 3D does a good job of simplifying the process by providing access to the convert command through the Point Cloud’s contextual ribbon tab.

When requesting data from an outside source, it’s best to include specifics on what information and what file format you wish to receive data in. For example, many scanners may include color information, intensity values, and normal values for each point. If you wish to use the additional Point Cloud Styles that are linked to color or intensity information, that data should also be requested.  If you want to simplify your dataset to just what is necessary to generate a point cloud in your drawing, all that is required are X, Y, and Z (or N, E, Z) coordinates.

So as you can see, a Point Cloud isn’t always just a Point Cloud. Depending on where the data came from and what format it’s in, it may be an AutoCAD entity or it could be a Civil 3D Point Cloud object.

Matt Miyamoto, P.E.
Infrastructure Solutions Application Specialist

Matt is a licensed Civil Engineer in the state of Hawaii. Matt obtained a BS in Mechanical Engineering from the University of Hawaii at Manoa, and has 7 years of private sector design experience which he applies in his role as an application specialist with Ideate, Inc. His project experience includes residential and commercial site development, private and public sewer, water and drainage systems, harbors improvements, and roadway improvements. While in Hawaii, Matt was involved in multidisciplinary projects for City and County agencies, State Departments, the Army COE and private developers. @MattM_PE

Get it. Know it. Use it.