Mapping & Surveying
Drones are being used more frequently by surveyors and engineers for terrain assessments and mapping. The notion of using photogrammetry for this industry is not entirely new, but the concept of drone implementation has made inspections and mapping much more cost effective. Accuracy is a critical factor during drone use within this industry. One of the most important considerations when using drones in surveying and mapping are the tools needed for proper accuracy.
Accuracy is divided into two categories; relative and absolute. As an example, a single ‘flown’ project may involve 200 photos processed and stitched together using a separate software package. In this case the final image output is very large, with all individual photo elements relative and accurate within the entire image. Though the image is not an exact scale, each image part is proportional to the whole photo, although a side-by-side comparison to an element outside the photo would reveal an incorrect proportion. To achieve accurate proportioning inside and outside the image, accurate ground control must be set.
Ground control setting involves the measurement of points seen within a photo with a very accurate piece of equipment. This measurement then allows a proper adjustment of the photo to match specified coordinates. This process is usually completed with a survey grade GPS system. Start by collecting the coordinates of each ground control point by determining the X, Y and Z axis. The geo-location of the project will be corrected once that data is input to the processing software, delivering absolute accuracy. Objects both outside and inside the project are now accurate to one another, along with proper scaling of the project. This provides a 3D representation of the project, which can also be used to measure areas within the image.
Benefits of Using Drones for Mapping and Surveying
There are several benefits to drone usage for the above applications, as they are widely adopted to assist in mapping and surveying.
Reduced Project Time
For centuries, surveyors were tasked with walking to cover the land they surveyed. This could be very demanding and time consuming to say the least. Just imagine walking a 200-acre piece of land to find the property corners in order to determine the topography of the land, not to mention having to deal with the vegetation that may exist on the property. Today, we with surveyors and engineering firms can use a drone to assist in these tasks.
Increase Data Accuracy
We use Traditional photogrammetry is now allowed in open areas for image collection, which is then processed into measurable data. Light Detection and Ranging, or what is referred to as LiDAR can be utilized in areas containing dense vegetation. Originally developed in the 1960’s, LiDAR systems were too large and expensive for drone use, however new technology now allows placement on some larger drones. LiDAR drones facilitate land surveying in challenging environments where field crews were previously needed. LiDAR can also be used to measure power lines for sag, which is very difficult and time consuming by any other method. Drones will not replace the need to locate the property corners by hand, but they are beneficial in many other areas that are very labor intensive, which makes drones much more efficient.
Return on Investment
Drones have become a viable solution for the surveying and mapping industry for two primary reasons:
The development of lighter and more efficient batteries that in turn increase the flight times of the aircraft. This increase in endurance allows operators to cover enough area to make it worth flying the missions.
The development of high-resolution cameras light enough for drone placement, allowing the accuracy needed to use them for this application.
For decades, surveyors and engineers used photogrammetry with manned aircraft to collect photographs of the earth to assist in mapping and surveying, but it was very expensive. It was necessary to use aircraft outfitted with the proper camera, along with a photogrammetrist to analyze and process the photos manually using a stereoscope. Now, our UAVs can be configured with high resolution drone cameras and drone software, as opposed to sending images to a photogrammetrist.