Many surveying applications can now be performed or enhanced by drone technology. Service providers are quickly realizing that a drone with direct geopositioning abilities is a must-have tool for their varied surveying tasks. A drone with direct geopositioning capabilities makes acquiring, creating topographic and volumetric data, and other aspects of data analysis more accurate, easier and faster. Thus, providing a much-needed technical advantage in a highly competitive field. There are many applications for drone mapping:
A direct geopositioning system monitors the position of a drone to a high level of accuracy, synchronizes this position to camera events and records information that can be used, in a post-processing step, to provide a priori estimates of the camera location for each acquired image. A direct geopositioning system is used to reduce the amount of ground control needed to achieve a specific level of accuracy or even eliminate it altogether in some cases, making direct geopositioning a tool that can improve both the accuracy and financial bottom line of projects.
The detailed modeling performed in a typical drone mapping workflow uses a rich data format called a Point Cloud. However, most CAD and GIS software requires a regularized grid of elevation “posts” as their elevation model input. For example, a gridded elevation model with a post spaced on 1-meter (3 feet) intervals might be the preferred format for a CAD-based analytic operation. These Digital Elevation Models (DEM) are derived from point clouds that have been “classified” such that only ground points are used in generating the elevation model.
Borrow Pit Analysis is a differential volumetric computation. It is a specific application of cut and fill computations used in earthworks analysis. The goal is to determine the change in volume over time. This change may be a cut (where volume is decreased) or a fill (where volume has increased). For example, if you are selling dirt from a borrow pit, the analysis is used to compute how many cubic yards/meters have been removed since the last time you conducted an analysis. Drone mapping is an excellent tool to use for differential volumetrics. The frequency of analysis is typically too high to support the high cost of manned aircraft remote sensing and the sites are often small enough to make drone mapping practical. However, great care must be taken in assuring consistent vertical references for the data.
It is frequently the case in volumetric monitoring that an established base geometry needs to be used in the computations, regardless of the current topology. For example, a site may have been surveyed prior to the placement of stockpiles. After a period of time, the ground disturbance is such that this original base line data can no longer be directly measured. Instead, the measured baseline data must be added during the analysis process as a priori model constraints. Using model constraints requires specialized analytic software as well as high vertical accuracy relative to a common datum.
Topographic (”Topo”) mapping is the process of creating a three dimensional (3D) model of the terrain (ground) of a site from data samples collected at the site using a drone-borne sensor. The output products can include digital contours, digital elevation files, cross sections, triangle models or discreate point models (point clouds). Source data for topographic mapping can be collected using either a dense image matching (DIM) technique or airborne LIDAR.