I find boundaries in general to be quite interesting. One type of boundary we have talked about recently that I find particularly interesting are those enclosing Air Space Parcels. While they are not common in places like New Brunswick, they are used heavily in some parts of the country, particularly in cities like Vancouver with significant numbers of tall buildings.
The idea of demarcating a boundary on the ground is a pretty simple one which is easily understood my most if not all. One can place markers on the ground and easily see precisely where the boundary is at all times and how structures relate to those boundaries. In the case of the land moving locally due to settling or other, markers move with the land and the boundaries persist in the same relationship to structures on the land as they are defined by the monuments in many cases.
An airspace parcel on the other hand is different. It is referenced to 3D geodetic coordinates meaning several things. First of all, there can not be markers placed at the corners of the parcel as it is just a point in the air. This makes it much more difficult to ascertain where they are. They can also have complex three dimensional shapes, making it even more difficult. Also, given they are referenced to geodetic coordinates rather than to ground monuments, if the ground moves locally, it moves with respect to the geodetic coordinates.
In the case where an airspace parcel contains a floor of a building this can be problematic as parts of the floor can become outside the airspace parcel quite quickly, and for everything to be neat and tidy legally, one must redefine the boundaries of the parcel.
In thinking about this, something we are expecting any day now on the West Coast is "The Big One". This would be an earthquake of magnitude 7.0 or up which is long overdue given historical evidence. Given the use of airspace parcels, and the fact that land can shift horizontally and vertically by meters in an instant in a large earthquake, Vancouver surveyors will likely be very busy following "The Big One" resurveying airspace parcels.
On a different note, but somewhat similar, I am very curious to see what happens with the land rights of the people displaced by the long lasting eruption on Hawaii last year. Hundreds of properties were completely obliterated and covered with many meters of fresh lava flows. I am very curious to see what happens to those properties as it is highly unlikely they will now be suitable to build on.
Interesting entry. Remember always to include citations and references.
ReplyDeleteVery interesting post! Airspace parcels are one of the most fascinating things in surveying in my opinion, and it seems as though they are only becoming more prevalent and important. As Canada (and the world) continues to urbanize, the tall buildings that already dominate cities like Vancouver and Toronto as you mentioned will start to be commonplace everywhere. This makes defining, locating and measuring airspace parcels more and more important in our world, and I think that it will be interesting to see the technology and developments that come along with the need for better placing of airspace parcels. As surveyors, I think you're right to say we'll be busy in the future!
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