Flutterby™! : I feel the earth move under my feet 2004-12-20 21:24:08.741907+00

I feel the earth move under my feet

2004-12-20 21:24:08.741907+00 by Dan Lyke 4 comments

So while I've been whining about moving reference points and survey lines, I've been ignoring the other issue: What happens when the land is moving? It turns out that California law covered that in the Cullen Earthquake Act, but this act is being interpreted as applying only to sudden movements, not long slow slides. SFGate covers some of the current issues involved: When property lines run through the front door: The slowly shifting ground in the Berkeley hills area means the land that's yours today may be your neighbor's tomorrow.

I have wondered about such things where I live, on the steep slope of Signal Mtn. Since 1989, when my house was built and foundation set, my house has not moved in relation to it's surroundings, yet I am sure that over the next few hundred years it will be not only measurable, but something you could easily see.

This is one of those cases where technology (GPS, Long Distance Laser Sightings) is a bad thing compared to the old way, where survey markers were pounded into the ground and landmarks were used for reference. And this is a case where 'law' and common sense collide. If the whole neighborhood is sliding, is there new land being made on one end, as the other end slides into the ocean?

i grew up being told that california was going to slide off into the ocean. this article by sfgate just proves it!

In Chicago the issue used to be creating new land. Back in the 19th century a garbage scow owner named Cap Streeter ran aground in Lake Michigan on a sandbar. He stayed there and sand silted up around his boat until he had a couple of acres of more or less dry land. He declared himself the independent city of Steeterville and ran ferrys the 100 or so yard to the Chicago shoreline so people could entertain themselves at his gambling houses, brothels and Sunday saloons. The city tried to annex the land, and Cap fought them for years, but eventually they wore him down. The city did throughout that period do a lot more deliberate landfilling (my Great-great grandfather worked on it), and the Steeterville neighborhood is now where Chicago's most elegant shops and residences are found, including the John Hancock Center, which is about where Cap ran aground.

However, some better lawyered people did take a lesson from old Cap. The Chicago Tribune owns some very valuable property along the lake front behind their building on Michigan avenue. Apparently they build a breakwater and let it deliberately sil up, then moved on the land. They got away with it, I guess because they didn't promise beer on Sunday.

Temporal accuracy is another hot-spot in geographic data. A simple example is the car navigation system that has older street data and sends the driver the wrong way on a one-way street after the street was changed from two-way to one-way. Is the navigation system faulty? Is the manufacturer at fault?

Cadastral mapping (defining legal land platts) is still based on control monuments and is generally cosidered a seperate field from GIS. You have to be a licensed surveyor to be able to create legal land platts and generally, surveyors are bonded and insured so that their clients have a way to receive compensation for errors. In actuality, however, the definition of the legal boundaries of land tend to not get changed much and are generally the liability is managed through insurance.

And if you think California has it bad, just wait until the ice caps start melting. I'm going to be buying some ocean-front property in Kansas!