Why Your Surveyor Should Be Using LiDAR
By Josh Lewis
How many times have you been in the middle of permitting a project when it gets put on hold because the municipality needs more information? Maybe they want to know if the specimen tree on the neighbor’s property is going to be impacted by the development, or perhaps they want to determine flood elevations for the stream going through the site, or maybe they need a “distance survey” for a site.
If your surveyor used LiDAR to generate your plans, then you’re in luck. The data is already in the can. The surveyor’s CAD department can update the survey and issue a revision, typically within 24 hours. That’s because when the survey is prepared using LiDAR technology, all that information (and much more) is captured.
How is LiDAR Different?
A LiDAR scan creates a 3D snapshot of everything that is visible at the time the survey is conducted. Basically, if light reflects off an object, it is captured. If your surveyor is using LiDAR for your project, you should expect three improvements over a typical survey — faster delivery, value added service, and a more accurate survey.
With airborne LiDAR, an unmanned aerial vehicle (UAV) is flown at low altitude over the site while scanning a million points every two seconds. This creates what is called a point cloud. Each of these points represents a three-dimensional coordinate in space. The points can then be used to create a topographic map, measure tree size, confirm cut and fill volumes, determine flood elevations, and measure site distances. All this information is captured in mere minutes (versus weeks when compared to a traditional survey crew using GPS) when the site is flown. That means there’s no need to visit the site more than once.
LiDAR is a Value-Added Service
This is most apparent when more information is needed that would usually require sending a surveyor back to the site to take additional measurements. It happens all the time — the neighbor calls up an arborist and complains that earth moving work is going to damage the root system of his 38” tree that’s close to the property line. Typically, the survey crew must go back to the job site and locate the tree on the neighbor’s property and then add it to the survey. Revisions like this can take weeks. Another example of LiDAR as a value added service might be when a city engineer needs a flood study done on the stream that crosses the property. Again, all this information has already been captured and can be created from the original point cloud. LiDAR is an investment that saves both time and money.
LiDAR Accuracy
To be clear, the accuracy of LiDAR it is not more precise than a traditional survey using a distance meter and a total station, but it is less prone to errors. So much human input goes into a traditional survey; from measuring up the total station and adjusting the rod height measurement and prism offset, to measuring tree diameters and correctly orienting instruments. All these measurements are read from a tape and then input into a field computer. A good surveyor builds in checks that prevent errors, but mistakes are inevitable. Not to mention that just keeping up with which trees have been measured can be a challenge. It’s easy to lose track of which trees have been counted and which have not when standing in the middle of a forest. LiDAR takes the human element out of the process making the data more accurate.
Normally you can’t have it faster, cheaper, and more accurately, but with LiDAR, you can. If the site is over 2 acres, then airborne LiDAR becomes a cost savings alternative for the surveyor. If the site is complicated or litigious, then LiDAR can save you no matter the size of the project.
Georgia Land Surveying wants to save you time and money with our state-of-the-art LiDAR technology. Give us a call today at (404) 255-4671 to learn more.