While the above discussion describes one short comeing of the Helmert blocking system as we are using it, the counter point is that it allows us to solve much larger problems than we could otherwise handle and it will allow us to include much larger amounts of real data in these adjustments. While the numerical tests done thus far do not prove that the technique will always provide good results they do indicate that it is working well in our current applications. We will continue to monitor the pros and cons of the technique and we do hope to show in the near future that the large amount of data that we will be able to handle will produce even better results than we have been able to achieve before. The nature of the network and the problem to be solved usully suggest an approach as to how the data should be devided. The process of designing the groups of data called blocks is often thought of in terms of regions or geographical areas but there are other ways to think about how to divide up the observational data.
Time is another dimension which is a natural blocking factor.
One method of blocking the data which is based on a geographical concept would be to divide the sites in the network into geographical regions with an approximately equal number of sites. Each region can then be processed independently with the Pages program as is usually done for any network, with one exception. In order to connect the regions into one complete network one baseline should be selected to connect two adjacent regions and the observations from this baseline should be assigned to only one of the adjacent regional blocks. The site in that baseline not originally included in the block into which the observations are to be assigned must also be added to that block and it thus becomes a junction site by virtue of being in more than one block. Each region only needs to be connected in this way to one other adjacent region but the connectons should cause all regions to become one complete network.