[PRCo] Re: Pondering the Planning Bureau maps

[Donald Galt]

On 8 Jan 2007 at 10:25, robert netzlof wrote:

> I'm puzzled. In the margin of each sheet one finds the number of
> adjoining sheets. Out in the fringes, those numbers still appear
> calling out neighboring sheets which:
> 
> 1) would be completely outside the city limits
> 
> 2) are not available on the web site
> 
> But I'm puzzled. If the sheets were a product of the city's Bureau of
> Planning, I can understand why they would not expend resources in
> compiling maps for areas outside the city. Given that, why assign
> sheet numbers for sheets which do not and would not exist?
> 

I'm quite sure the missing sheets were never published.

The sheet numbering scheme is a very idiosyncratic clockwise spiral, with no 
gaps whether or not a sheet exists. Given the scheme's logic, it is reasonable 
that skipping numbers past gaps would have created chaos. And if they had 
instead used a line-and-column grid, nobody would be raising questions about 
missing squares.

Also, suppose that during the history of the mapping project the city annexes a 
borough or township. All of a sudden, two or three or thirteen previously 
unmapped sheets are added to the cartographers' list.

What fascinates me is that where a sheet is published, there is generally no 
break in detail or quality on crossing the city boundary. So, in effect, the 
city of Pittsburgh has given us a whole heap of bonus territory. 

Glass half full!

Don G