GPS Network Services For Supporting Surveying Tasks.
A reliable network service providing high quality and high fidelity solutions would no doubt generate significant revenue.
A justify and paradigm shift
Instead of broadcasting corrections and placing the onus of obtaining a final solution on the user and his equipment a service provider can organize a specific service by taking advantage of an existing network systems infrastructure to compute his coordinates pre-broadcast in the required reference system. Final (position) solutions for all logged users would be simply computed as a by-product of the continuous network processes – all the time within the quality and integrity criterion implemented at the network administrator level. After all, there exist already a number of web-based services used to generate coordinates from the post-processing of data sent by the user. It is just an extension of this functionality to real-time processing.
This concept is certainly worth investigating! Currently, providers of GPS corrections have no control on the quality of the results computed by the user. This makes it difficult for them to justify charging for their services.
The very concept of virtual reference stations has spawned from the unarguable fact that rover-based RTK solutions exhibit inherent and historic biases, particularly of distance-dependency. This has led to the development of an even greater number of solution algorithms to tackle this problem. The current approach proposed by the RTCM standards committee will only compound the difficulties by forcing the burden of computational work onto the rover firmware. Overall this situation leaves providers in a weakened position to charge for their services since they do not have any control on the quality of the solutions generated in the field.
Therefore, we believe that a paradigm shift is required in order to meet the expectations of future network operators.
Conclusions
This new mode of distributing GPS RTK solution contradicts the data flow in classical RTK by asking the field user to transmit the GPS observations to the control centre. This facility can select the optimal combination of stations to compute the best possible position before returning the result to the user.
The advantages of this approach are clearly evident. A GPS Network provider can exercise control over the generated products and, as a result, place a commercial value on the service, especially as the typical user is released from the obligation of learning complicated GPS surveying techniques. Safeguards, and thus integrity, can also be easily implemented into the distribution service; if the number of satellites is too low, the geometry unfavourable, or the multi-path effects detrimental, a message can be sent back to the user warning them that the provided solution is not optimal and that it may not meet their specifications. With the critical processes (legal minefields) of traceability and integrity looming on the horizon of positioning services, these grey areas are becoming much darker and need to be considered in any long-term plans by deciders involved with GPS positioning services.
An added benefit to this approach is the decreased burden placed on the rovers by removing the need for field calculations, thus encouraging the development of a new generation of less costly rovers. These no-frills (stripped-down) receivers are already beginning to hit the market.
The same data may be transformed into a specific GIS format, or also used as input to topographic processing software for real-time visualizations. Other services may be incorporated such as the transmission of coordinate files, or portions of digital maps, etc.
As a further evolution, it may even be desirable to incorporate total stations in the network infrastructure for handling the data processing either in real-time or in a post-processed fashion. We can envision the natural extension of these services to civil engineering works and elsewhere.
This concept is simply based on the efficient use of available communications infrastructure and software solutions allowing decision-makers to completely fulfil their functions and responsibilities, effectively, by implementing a complete new solution to their users.
There is no doubt that other emerging technologies will take part of the solution. The Internet based services have already demonstrated their capabilities to exchange data in full duplex mode and in real time. The rapid growth of the third generation of wireless communication media will fit perfectly the request to have Internet access from the field.
Finally, all the elements are in place for providing to the professional surveyors, and for the emerging new non-surveyors community well identified services with clear values. The services associated with a GPS Network infrastructure are the key to entering in a digital world of information where the location will be as natural as the time of day on your wrist.