Department of geomatics engineering, the university of calgary, alberta, canada
Mobile Mapping Systems (MMS) are capable of providing fast, cost-effective, and complete data collection. Their development has been motivated by a desire to overcome the problems with alternative methods of spatial data collection. This paper presents a review of land-based mobile mapping systems – including their history and principle of operation
The idea of mobile mapping, i.e. mapping from moving vehicles, has been around for at least as long as photogrammetry has been practiced. The early development of mobile mapping systems (MMS) was, however restricted to applications that permitted the determination of the elements of exterior orientation from existing ground control. About fifteen years ago, advances in satellite and inertial technology made it possible to think about mobile mapping in a different way. Instead of using ground control as reference for orienting the images in space, trajectory and attitude of the imager platform could now be determined directly. This has made mapping independent of pre-established ground control. Hand in hand with this development went the change from analog to digital imaging techniques – a change that has considerably accelerated over the past few years. Integrating the concepts of kinematic trajectory determination and digital imaging resulted in multi-sensor systems capable of acquiring, storing, and processing geo-referenced digital data, thus providing a complete solution of the mapping problem with data from only one platform. Systems that use geo-referencing and digital imaging as integral parts will in the following be considered as mobile mapping systems, independent of their area of application.
Combining the advances in digital imaging and direct geo-referencing has not only increased the efficiency of mobile mapping considerably, but has also resulted in greater flexibility and lower cost. In addition, it has integrated two branches of our discipline that for too long have gone their separate ways – geodesy and remote sensing/photogrammetry. These MMS, which can be used as an alternative to both point-wise GPS and traditional techniques of data collection, integrate various navigation and remote sensing technologies together on a common aerial or land-based platform. They capitalise on the strengths of the individual technologies in order to increase the efficiency of data collection. They have in common that they integrate a set of sensors mounted on a common platform and synchronized to a common time base. They are typically used in kinematic mode. In principle, they are capable of operating with the data measured on the platform. No other information, such as known ground control, is needed, although it may be included as redundant information. Systems of this type:
- Can be immediately deployed everywhere on the globe without the need for identifying existing ground control
- Employ a task-oriented system design through integration at the measurement level. Data flow optimization can therefore be a built-in feature
- Can be equipped with real-time quality control features by including data redundancies in the system design and by using a combination of real-time data processing and expert knowledge to get homogeneous results
- Generally use software georeferencing to transform the time-dependent measurement process into a sequence of georeferenced images which can be considered as independent geometric units in post-mission processing
The most important benefits of MMS are a reduction in both the time and cost of data collection; however, they also have a number of additional advantages. For example, both spatial and attribute information can be determined from the remotely sensed data. Furthermore, data can be archived and revisited – permitting additional data collection without additional field campaigns. Systems with these characteristics are likely to play an increasing role in Geomatics engineering.