Mobile LiDAR – How Does It Work?

This can be extra than you want or want to know about the complexity of a mobile mapping gadget (MMS), however for the ones of you involved, right here’s an explanation the common Joe can apprehend. When you have got a Mobile Mapping System to arrive on your process web page to carry out a laser test, the machine seems like little greater than a fashionable piece of PVC strapped to the top of a 4 wheel drive SUV. Don’t be fooled by its easy look. Inside is a current miracle… A fashioning together of impartial and amazingly complicated structures that, while brought together, produce what could have regarded impossible now not goodbye ago. This little white field of surprise, when fired up, begins speaking with as many satellites in the area as it can locate. Positions are hooked up. Movement and headings are monitored at breathtaking velocity with each studying time stamped so that every few seconds, whilst the computer catches its breath, the impartial pieces of facts are flawlessly spliced again collectively at the side of complicated corrections to show a stylish replica of the floor that became just pushed beyond. It is sincerely a factor of splendor.

Tech-savvy MMS vendors use this amalgamation of technology to provide its customers with cellular laser scanning services that produce an X, Y, Z factor cloud in State Plane or comparable coordinate systems. Here is an outline of the various techniques used and the way they tie together to generate an accurate 3-D description of the regions surveyed:

How To Determine Position – GPS

Mobile Mapping Systems (MMS) use the Global Positioning System (GPS) to decide wherein we’re at a given factor in time. The accuracy of the uncooked GPS facts isn’t good enough for our purposes so we use certainly one of three technology to correct the raw function information. If we have a recognized manage factor close to the job, we can set up a GPS base station over that point and use measurements of GPS position from the satellites to determine the difference among the measured and actual position of that factor every second. This error or “differential” is then transmitted by using radio hyperlink to the Mobile Scanner and the GPS information gathered with the aid of the Scanner each second is corrected. This technique is referred to as Real Time Kinematic or RTK. If no manage factor is to be had, we are able to establish one and, the use of industry preferred tools, determine its actual location at a later time. Using RTK, we will establish our position to inside ±1 inch in Easting and Northing and ±2 inches in elevation.

The second technique we use to determine our position is much like RTK, however, is named Virtual Reference Station or VRS. In this approach, we join a service that has a number of base stations (the VRS Network) installation in a given region. We use wireless information links to get the GPS corrections from this Network and the records from the GPS on the Mobile Scanner is corrected as inside the RTK technique. The accuracy of this machine is similar to RTK.

The third method we use to decide position makes use of OmniStar®, a personal satellite-based correction carrier. It gives corrections in a way much like VRS besides that we use a satellite tv for pc receiver to get hold of the statistics as opposed to a wi-fi link. The accuracy of OmniStar® is barely much less than RTK or VRS at ± four inches. We can blend and healthy those technologies as necessary – as an instance, we will use RTK to do the test, however, outline the manipulate point using the OmniStar® system to do away with the need for determining the manipulate point function later.

How To Measure Changes in Direction – Inertial Measurement Unit

Using our GPS generation, we degree our role as it should be about once according to second. However, we are constantly changing the route. At five miles consistent with hour, we tour approximately 7 feet in step with the second. During that second, we may additionally trade our direction of the journey (heading) by many tiers. The inertial size unit (IMU) measures modifications in scanner heading 100 times in step with 2nd. The accuracy of the IMU is ± zero.1 tiers (~ zero.17 toes at a distance of one hundred ft away). The function of the Mobile Scanner is automatically reset whilst it gets a brand new GPS role “restoration” every 2d so any small errors from the IMU aren’t always allowed to build up.

How To Collect Data of the Topography – The Laser Module

Using GPS technology and an IMU, we will hold tune of the exact position of the Mobile Scanner at each factor in time. The GPS and IMU are both set up within the scanner housing. Outside the housing, we have a rotating laser module. This scanner has a distance measuring laser hooked up at a right attitude to the route of the journey of the vehicle or vessel. The laser measures 36,000 factors a 2d, rotates up to ten RPM and has a number of up to 450 toes. The accuracy of the space size is ~± 2 inches. The distance between factors is managed with the aid of the laser RPM and the speed of the automobile. We commonly generate a factor cloud with factors ~zero.5 to 2 ft aside. The statistics may be thinned to lessen the scale of the statistics sets if favored. If higher statistics coverage is required, the settings in the control software program may be modified. The Mobile Scanner can experiment something it’s far pushed past above, under or to either side of the scanner.

How To Correct for Uneven Ground – Pitch and Roll Sensors

The Mobile Scanner is established to a vehicle or vessel. In an ideal global, the ground or body of water might be perfectly horizontal. Since that is obviously no longer the case, we accurate the information via measuring the pitch (uphill or downhill angle) and roll (left or proper angle) of the scanner the usage of pitch and roll sensors. These contraptions measure pitch and roll one hundred instances consistent with second to an accuracy of ± 0.01 ranges (~ 0.02 feet at a distance of one hundred ft) Because these instruments degree the mindset of the Mobile Scanner so regularly, we can journey over rough terrain or in rough seas at affordable speeds without seriously impacting the accuracy of the statistics.

Summary

Mobile LiDAR or Mobile Scanning as it’s far once in a while called can offer previously extraordinary performance and accuracy in many survey packages. Whether you want to measure the volume of your stockpiles, do distinct mine planning, degree seaside erosion, determine plant life encroachment on utility proper of ways or resolve a myriad of survey or engineering problems, Mobile LiDar may also offer the answer for your issues.