Outstanding in the Field

Introduction
Field users of GIS are not a homogenous group. The functionality that they require is as varied as the tasks that they are asked to perform, so it would be wrong to suggest that there is one enterprise-wide field “solution”. The users can be viewed as being on a sliding scale, from those who simply need to view data through to those who need the full functionality of their master GIS but in the field, with a wide range of requirements in-between. It may seem to be the “top end” users that most require an integrated solution between field and office, but in reality the efficiency of all users is reduced if both systems use different underlying data formats. The question must be, why are the two solutions so different?

Technologies
Let us first look at the various software and hardware technologies that are used by a field GIS and the limitations that these technologies impose.

Software
In terms of the integration of field and office use, the most important aspect of the GIS software is the relationship between the master and field systems. The principal relationship models are:

Thin Client. In this model the field software is basically just a user interface. All (or at least most) processing is done by the master system, which also holds all of the data. This requires that the two systems have a continuous fast communication link between them as each operation on the field unit is actually sending a request for information to the master system.

Thick Client. This is similar to Thin Client, but more work is done by the field system. In a typical Thick Client application, the field system would request data from the master and then perform operations upon it locally. A more intelligent (thicker) client may cache data to improve performance. Again there is a requirement for an open communication link as data is being passed between the two systems as it is used.

Independent Systems. In this model, the field system holds all of its data locally and all of the processing is carried out on the field machine. To be useful, this model requires periodic communication between field and master systems to synchronize data. Unlike the other two models however, this can be done in a batch operation, for example by connecting to the office LAN at the end of the day. Because the data is held locally on the field machine, users who do not know the geographical area that they will be working in need large amounts of storage capacity. This model is often referred to as a disconnected field GIS.

Clearly the choice of model is dependant upon the use to which the field GIS will be put. Client-Server applications rely upon wireless communications, but for particularly data intensive operations the available wireless bandwidth may not be sufficient.