4 replies to this topic

[Nick Springer]

by Dan Charles

NPR Weekend Edition - Saturday, February 25, 2006 · Sophisticated new maps are being developed that are based not on street addresses, but on coordinates. The maps could speed rescues and general response to disasters like Hurricane Katrina.

http://www.npr.org/t...storyId=5233408

[mdenil]

Some years ago I worked for the Prairie Farm Rehabilitation Administration (PFRA), an old 1930's holdover and a part of Agriculture Canada. The Canadian west uses a similar land survey system to the western US (with some differences; like an origin in the south east instead of the north east), but it doesn't cover everything. There are a large number of anomalous tracks as well (Mati settlements in Manitoba, townships with no ranges in BC, etcetera).

The PFRA is responsible for the whole of the Canadian Prairies, so every parcel down to quarter section plus all the anomalous parcels has a unique PFRA designation. It is a 14 character / numeric code that packs a description of the location in the Western Land Survey System and includes modifier flags to change the meaning of certain character groups to accommodate the (usually older) systems the survey overran.

In the late 1990s there was extensive flooding, particularly in the east, and huge tracks of featureless land was submerged. Everyone (outside of towns), however, knew their PFRA designation, and, as it was designed to incorporate all the land description designation systems, it was the system used for location finding and navigation right across the flood zone.

I had left the PFRA by then, but while there I had played a (very small) part in expanding the system to 14 characters and thus the comprehensiveness of the designation.

M.Denil

[Nick Springer]

The NPR segment focused a lot on the use of the "National Grid" by Federal emergency responders, and the contrast with local responders who rely on street address, not a grid system.

One interesting point was one of the commentators suggested that all maps shoul have a National Grid overlay to promte its use. Is the geodata for this grid system easily found?

[Martin Gamache]

They are confusing index grids and positional grids in this piece.

In facts there are several grids and are related somewhat to projections.

The grid they refer to in the radio piece or Military grid is known as MGRS which is a modified UTM grid MGRS and UTM.

The notion that all commercial maps should use one standards grid is ludicrous since all the states can't even agree on what to use. That's why we use to have public agencies that produced good, accurate maps....

The real nugget in this feature is that E911 responders can't take geographic coordinates (in whatever format as an input yet).


It's 2006 and we've had two major disasters in this country since this century began....and the burden should be on commecial map companies to implement a grid system....is my tax money being spent on crack? I bet Iraq will be better mapped than the US by the time we pull out of there.


mg

[mdenil]

Since a grid system is a linearly measured, as opposed to a angularly measured, system, any country the size and configuration of the US would have to employ multiple base meridians to correct and limit the increasing disagreement between grid directions and geographic directions. Any 'national' grid would be tied to a multiple zone system like UTM, the Canada Western Land Survey System (or whatever the proper name for the US equivalent) or other such systems.

Just, as is mentioned above, it is important not to confuse index and positional grids, it is important as well to not confuse local survey systems (like State Plane) with such a national location grid. There are many such systems, not because States cannot agree, but because low error is more important in such cases (land survey) than wide applicability of any particular system.

I find even a lot of GIS techs get all balled up with UTM zones. I think it unlikely the general public would take to it. Consider BC, where hunters are required to carry topographic maps and record the UTM coordinates of the kill site: a very large proportion of reported sites are out in the Pacific....

Most 911 and other emergency systems are set up exclusively on address finding, with addresses on single line street networks. As I recall, one such system I worked with used the local telephone company's street data: the problem there was that it didn't include streets without telephones. that was something of a problem.

M.Denil