Aerial imagery aids crane location precision
02 April 2018
A sure indication of progress, growth and expansion is the erection of a large, sky-scraping crane on a jobsite. Whether a fixed tower crane hoisting steel beams for a skyscraper on the San Francisco skyline or a huge crawler crane that is lifting and installing new tanks at an expanding water treatment facility, cranes of all types are a common sight in urban and rural landscapes.
Determining where to place a crane on a jobsite is an important element of the crane’s performance. Heavy lift engineers must plot out the exact placement of one or more cranes, and they often spend many hours reviewing sitemaps, walking and driving around the jobsite, testing ground samples for stability, surveying water table studies and measuring bridge clearance and traffic right of ways. This must be done to create a thorough proposal for the site manager or property owner.
Heavy lift engineers are now looking to the skies when mapping job proposals that show where cranes should be placed. Through the use of high-resolution aerial imagery captured multiple times a year, heavy lift engineers can more easily identify worksite obstacles, confirm ground conditions and articulate transportation and proper location of the crane.
1. Hedging hazards
When prepping for crane placement and erection on a busy construction worksite, there is rarely going to be a straight line from the center pin of the crane to the object to be hoisted and then to that object’s destination. There will inevitably be multiple obstacles that can interfere with safe crane operation, from obvious buildings and trees, to less-noticeable stairways and power lines. It is extremely difficult to gain a clear visual sightline of the entire worksite from ground level.
Through accurate overhead maps, heavy lift engineers can obtain a bird’s-eye view of the entire jobsite, zooming in on specific obstacles to effectively mitigate risks. Surveying these images from the office, engineers can view power lines, bridges and pipelines. They can also capture height measurements through oblique imagery. Those measurements can then be verified by the onsite project foreman.
When making repairs or installing new equipment at an oil refinery, for example, crane location precision is pivotal. By viewing recently captured aerials of the refinery, engineers are able to identify optimal crane placement locations and capture specific radius measurement from the center pin of the crane to the location of the object(s) that will be hoisted. Engineers can more specifically determine the type and size of crane needed. Being able to make those determinations all from the office, without spending precious time out in the field, is not only convenient, but also a significant cost savings during the proposal stage.
2. Confirm ground conditions
Improper installation of a crane is one of the leading causes of catastrophic construction accidents. Unexpectedly soft, marshy or unlevel ground conditions not identified during initial onsite visits can hinder proper blocking and stabilization of any sized crane.
Through aerial view maps captured at different times throughout the year, heavy lift engineers are able to thoroughly survey and assess ground conditions surrounding a worksite, observe possible flooding patterns and areas that tend to puddle heavily after rainstorms and identify any potential trees or shrubbery that might complicate crane sites.
Obviously, a heavy crane set on a marsh is going to sink, but if those ground conditions are identified in high resolution maps of the worksite, engineers will be able to reinforce the ground by deploying engineered crane pads and mats and additional stabilizers to shore up the equipment. They may even decide to adjust the size or type of crane they use. Ultimately, the added advantage of those seasonally captured aerial images leads to a safer work environment.
3. Keep on truckin’
Placement and erection of a crane often means deploying a convoy of trucks, each carrying vital components that will be assembled once onsite. With as many as 40 truckloads traveling highways and surface streets to the destination, a concerted effort is put into the navigation logistics.
With many of those trucks being classified as oversized loads, heavy lift engineers must map out each mile of roadway that the convoy will traverse, considering bridge height and weight restrictions, culverts, power lines on surface streets, overhanging tree branches and other obstacles once on the worksite.
While the most recent satellite images may be years out of date and pixelated, engineers can now survey the entire pathway before the trucks hit the road. The height of every bridge along the highway can easily and accurately be measured. Low power lines and tree branches can all be identified and circumvented, ensuring there are no unexpected surprises along the journey.
On approaching the staging yard, with the help of aerial maps, the project foreman can then effectively direct the order each truck should arrive for easiest buildup of the crane. With 40 truckloads for example, truck 8, 9 and 10 can safely arrive in the yard first and have their pieces of the crane puzzle unloaded, while the other trucks wait outside the often tight spaces in the yard. This logistical plan alleviates any safety hazards often caused by a large number of moving parts.
By using high-resolution aerial imagery, heavy lift engineers can now more effectively and efficiently identify worksite hazards and obstacles, assess ground stability and map out convoy and installation logistics.