In an earlier article we reviewed some of the possible reasons why mobile mapping has not been openly embraced, while at the same time airborne LiDAR systems (ALS) are very popular. Lets continue to look at even more reasons, not directly related to ALS.
So far we have identified these areas:
There are far more competitive solutions to the use of mobile mapping systems (MMS) than ALS (RTK, traditional surveying, mobile devices, etc.).
There are many more potential service providers for MMS projects (surveyors and GIS data collectors as compared to aerial photogrammetry firms).
While ALS is certainly expensive, so is the photogrammetry alternative.
ALS is much less sensitive to weather and daylight factors as compared to aerial photogrammetry.
The list doesnt stop here though. In spite of the best efforts of some very good companies and technology evangelists, there are many issues yet to be overcome. Surveyors in particular generally do not believe that MMS can provide survey grade geo-referencing of the point cloud. To a surveyor the term survey grade implies 0.05 feet accuracy, or better, particularly for elevation. Surveyors are certainly aware of the limitations of GPS this is why total stations and digital levels remain absolutely essential as standard survey equipment. While 0.10 feet is fantastic for many purposes, it is not the standard expected for surveying, engineering, and construction.
GPS alone cannot provide this. Even with the synergy gained from combining GNSS and an IMU this consistent level of accuracy is out of reach. However, using methods of alternate positioning can make 0.05 feet something to be realized.
The most common method of doing this is by including higher accuracy control points spaced sufficiently to adjust the point cloud. For this solution to work, a good quality IMU must be used to generate a consistent and predictable trajectory. Fortunately IMUs are improving and becoming more affordable every year.
As a side note, it is sometimes possible to achieve survey grade results without control, using only the INS solution, but it is not a reliable means to do so. Its a bit more of good luck (perfect conditions and a good satellite constellation). This is really no different than using AGPS and IMU for aerial photogrammetry.
The availability of MMS-smart software is another issue. While there are several products available that can handle most MMS generated data, only a few are designed to take advantage of the MMS data. This includes the geometry, point pattern density, and also the use of the imagery generally associated with a MMS.
Many of the software packages, on the other hand, are designed to take advantage of static scan (TLS) data. Familiarity with TLS data does not necessarily extend itself directly into MMS. This can definitely lead to early frustration for users who think they have the software and expertise already in place to exploit the MMS data. A bad experience here can curtail further investigation of the MMS systems and technology.
Static scanning in many ways is a strong proponent for MMS while in some ways it discourages MMS. Whenever LiDAR becomes part of the solution to any project, this can be a benefit towards MMS. However, just as a non-robotic total station (under $10k) is often purchased instead of a much more productive robotic total station ($50k), the same can be said for the static and mobile scanners. Several (maybe even more than a dozen!) static scanners can be purchased for the price of a single MMS. Its a tough decision.
Not to be overlooked is the entire geographic positioning issue. MMS requires GNSS which adds more instrumentation and further understanding of surveying, mapping, and geodesy. Users of TLS looking to enter the MMS market suddenly find themselves encountering CORS, HARN, projections, geoids, datums, scale factors, and more. For many this can be overwhelming while others may embrace it without properly preparing for the necessary learning curve associated. In either case MMS leaves a sour taste with the TLS user.
The key for MMS proponents is understanding when it is appropriate and when it is not. Owning an expensive piece of equipment does not necessitate employing it on every job. It is more important to understand there are more and varied opportunities to exploit MMS and to build potential in new markets.
Now its time to introduce you to Snoopy.
Snoopy is the next generation of ScanLook from LiDAR USA. Snoopy is designed to be easy to build and maintain, ultra easy to use and transport, very configurable with INS and scanners, and affordable. It is not a toy. It is not a GIS-only solution. It is not a survey-only solution. It is a highly configurable mobile mapping system with nothing missing. It can sport one or more Velodyne HD32 scanners, FARO FOCUS scanners (including the new x330), or Z+F scanners. It can be quickly mounted to virtually any moving platform. It should be the impetus to get you into mobile mapping.