As the LiDAR market continues to evolve consumers are benefiting from more and better choices in the technology to capture as-built data. The original LiDAR scanner, about the size of a desk mounted on a tripod has now evolved in about 12 years to smaller, dynamic data collectors mounted on vehicles.
Now the power of 3D data collection is in the palm of your hand. The latest evolution in mobile mapping is the new ZEB1 hand-held mobile. The ZEB1 system includes a lightweight laser scanner mounted on a simple spring mechanism. As the operator moves through an environment the scanner loosely oscillates about the spring producing a sweep of the scene that converts 2D measurements into 3D fields of view. Its ability to self-register makes it ideally suited for use indoors, underground and other covered environments lacking GPS coverage, such as dense forest and urban canyons, where traditional solutions that utilize GPS dont function well.
In January 2013, the expert services of Terrametrix, led by Michael Frecks, PLS, tested the ZEB1 hand-held mobile mapper during a project to supplement data for overhead pole attachments in areas that were not accessible to the StreetMapper TMLS system.
Frecks has extensive experience in high tech 3D laser scanning as both an innovator in the industry as well as a consultant and advisor with over 35 years experience in the field of land surveying and then laser scanning technology. Frecks continues to push the envelope of his profession in striving for improvement of 3D laser scanning systems that accurately characterize as-is conditions, from field measurement and documentation to final deliverable.
You really dont know the power of new technology until you take it to its limits, said Frecks. The ZEB1 was originally designed for indoor surveying where GPS is not available. Because the basic concept is continued recognition of objects located in a scene through repetitive movement this becomes more complex in a less stable, dynamic environment like the outdoors. We wanted to test the range, accuracy and portability of having a scanner like this in our toolbox.
PROJECT SCOPE
We needed to obtain utility pole attachments through an urban environment encompassing 7 miles -approximately 300 poles. Pole attachments have always been a challenging acquisition in urban areas. The use of helicopters at a low altitude is disruptive. At a higher altitude the data is sparse. Traditional methods of measuring pole attachments are cumbersome and time consuming and can be prone to errors.
What we set out to do with LiDAR capabilities was to remotely measure pole attachment heights and locations in a non-disruptive fashion, said Frecks. Static scanning is very accurate but too slow. Our tools of choice were TMLS using the StreetMapper system and the ZEB1 in areas we could not access. Because of its light weight components, less than 1.5 pounds, the ZEB1 goes wherever you go. Its portability does not require a time-consuming set up or the requirement for lengthy data processing of static scanners.
The work process was to scan with TMLS first which took 1 hour. Then, a review of the data and coverage of the poles locating areas that lacked 100% coverage was supplemented with the ZEB1. There was a total of one mile in three different segments, approximately 45 poles, where the utility lines ran in the backyards of the residential areas inaccessible to 100% coverage from the street using TMLS. The ZEB1 allowed for documentation through access of the power line right-of-way. This provided rapid scanning of large areas at walking speed.
We spent approximately hour scanning in each of the 3 areas with the ZEB1, said Frecks. Two of the areas that together equaled mile were 300 feet from the street located in dense brush and trees. The ZEB1 performed well while climbing through briars, over fences, and through varying terrain. Although the ZEB1 was designed for indoor acquisition its small lightweight backpack and cabling had some of the same issues seen with outdoor, pre-blue tooth GPS where the cables were often snagged in heavy brush areas. This cabling arrangement did not create any undue issues but you did need to be aware that you were cabled between your hand and the backpack, explained Frecks. Blue tooth could solve this solve this issue but add to the weight of the hand unit.
High definition imagery was collected independent of the ZEB1 during the walking data collection. Although this could be acquired by one person, for safety reasons, the two-person crew performed very efficient with these combined technologies.
The field work process was a lesson in project planning. ZEB1 data collection began at a location where the last pole was identified as 100% coverage from TMLS. Progression along the pole line to the next area where 100% coverage of TMLS data was acquired, the ZEB1 data completed the scene by filling in the LiDAR data. Because the data was being merged with TMLS there was no need for GPS or a geo-reference solution from ZEB1. The ZEB1 data was translated and rotated into the TMLS geo-referenced data. Naming conventions of the ZEB1 file was key to coordinating these areas. Additional work-flow processes created by Terrametrix made for a seamless transition.
QA/QC was performed by comparing the ZEB1 data to the TMLS data. Because some of the areas were overlapped we were able to see the performance of the ZEB1. Although the ZEB1 data sets had more noise (0.10 thick) the power of averaging the data produced a final positional accuracy of 0.06 , said Frecks. Although the ZEB1 data had more noise it overlaid the TMLS data very well. This kept our work process of extracting pole attachments uniform throughout the project.
Although we did not upload the files from the field using a data card, ZEB1 data can be uploaded to the 3DLM International server via Dropbox at a price of $250.00 for 1km of data, measured as a unique distance. The data processing ratio is 1:1, therefore 15 minutes of data collection equates to 15 minutes of processing. After the data has been uploaded to the server it takes 15 minutes to process and then you can download the finished data.
Processed data received prior to leaving the field allows for assurance of data capture and coverage while deployed at the site. Keeping file sizes small allows for faster return of processed data. The one mile of ZEB1 data capture on this project was collected using six separate files. We had all six files processed and returned within one hour, said Frecks.
Although the ZEB1 was used on this project for only one hour the small lightweight battery lasted the entire time. You do have the ability for data capture all day long using multiple batteries with additional charging capabilities at your vehicle.
The ZEB1 sells for $22,000 per unit and it is available from 3DLM International, a North American distributor, based out of Denver, Colorado (720-214-3554).