West Penn Today - We move on!

[Fred W. Schneider III]

Ken and others:

If you've never worked with the topographic or topo sheets, they contain one
hell of a lot of detail.

Brown lines connect points of common elevation; the contour interval or
vertical distance between such lines is always printed at the bottom of the
map, and ranges from as little as 10 feet in relatively flat terrain to as
many as 100 feet in mountainous regions.  Most if not all of Pennsylvania is
down at a 20 foot contour interval.  Once you become adept at reading those
brown lines, you can actually and easily recognize mountains, valleys,
plateaus, etc.  And, if the abandoned railway was heavily graded, little
tick marks in the brown lines will show nicely where the cuts and fills
remain.  Contour lines crossing streams always point upstream; i.e., the
point on the brown line crossing the stream is always pointing toward the
source of the water, not the ocean.

Blue is used for bodies of water.

Green is used for some forested areas.

Black ink is used for man made objects up to the date of the initial
printing.  Purple is used for man made objects built since the date of the
original survey and added to the second, third, fourth, and subsequent
printings as a result of aerial resurveys.  Highways are two parallel black
lines; red is added for principal highways.  Cross hatched black lines are
... you guessed it ... railroads.  Dashed line were once used for abandoned
rights-of-way but I understand that has been dropped on newer surveys.
Buildings are indicated by small blocks (or larger if the scale is actually
larger). Specific symbols are used for selected buildings, for example a
cross indicates a church.

The term 7.5 minute indicates the portion of the earth that is covered.  For
those of you who have not had such training, there are 180 degrees of
latitude from north pole to south pole, and 360 degrees from pole to pole to
pole (a vertical circle around the earth.  There are 360 degrees of
longitude around the earth.  Within each degree, there are 60 minutes, and
within each minute there are 60 seconds.  That means 21,600 (60x360) minutes
of latitude or longitude on the earth, and 1,296,000 seconds.  It would take
162,000 maps measuring 7.5 minutes by 7.5 minutes to cover the earth in any
direction.   Note also that the lines of longitude taper toward the poles
and bulge outward at the equator.  The USGS topo sheets or quadrangles,
however you call them, taper slightly from the base to the top ... almost
imperceptibly ... but if you try to glue all those in Pennsylvania together,
you will find it does not work.  At the 40th parallel, a 7.5 minute map
covers an area of slightly less than 8 miles by 8 miles;  At the equator, a
7.5 minute map would be 8.33 miles across (width in minutes of longitude)
but at the north pole or south pole is would be zero.

The older topo sheets showed twice as big a chunk of the earth (15 minutes x
15 minutes) on a smaller piece of paper.  The plane table mapping techniques
left a lot to be desired; in many cases you simply cannot make a mylar print
of the old maps and enlarge it to the new scale and lay it on the new 7.5
minute map and have anything truly match.  There was, of course, some
grading and some erosion and some movement of roads but a lot more error in
the older maps.

Ed gave you an address where you can buy any maps in the country.  There are
also local dealers, usually stationary stores, newsstands, map dealers, or
even Borders Books, that sell local copies.  Look for map dealers in the
telephone directories.  You should be able to find one where you can look at
index maps and see what you want.

Before you spend a lot of money on West Penn or Pittsburgh maps, suggest you
first go out and buy one in your part of Nevada and see if they make any
sense to you.  It will be $4.00 to $7.00 well spent ... if you understand
them, then go buy other areas.  I'm not being demeaning, but my wife, and I
love her dearly, would never be able to understand them.  Some people would
be wasting money.




"Edward H. Lybarger" wrote:

> Available from US Geological Survey, USGS Map Sales, Box 25286, Federal
> Center, Bldg 810, Denver CO 80225.  The state indexes are free, maps are
> about $4 - 4.50 these days.
>
> -----Original Message-----
> From: owner-pittsburgh-railways at dementia.org
> [mailto:owner-pittsburgh-railways at dementia.org]On Behalf Of Kenneth and
> Tracie Josephson
> Sent: Tuesday, July 11, 2000 5:02 AM
> To: pittsburgh-railways at dementia.org
> Subject: Re: West Penn Today - We move on!
>
> John Swindler wrote:
>
> > Looking to trace a right of way?  Check the 7 1/2 min topo maps for
> streams,
> > and that's where to look.
>
> John,
>
> Where can I find these topography maps?  Ken J.
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