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Ken and others:
<p>If you've never worked with the topographic or topo sheets, they contain
one hell of a lot of detail.
<p>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 <b>always
point upstream; </b>i.e., the point on the brown line crossing the stream
is always pointing toward the source of the water, not the ocean.
<p>Blue is used for bodies of water.
<p>Green is used for some forested areas.
<p>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.
<p>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.
<p>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.
<p>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.
<p>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.
<br>
<br>
<br>
<p>"Edward H. Lybarger" wrote:
<blockquote TYPE=CITE>Available from US Geological Survey, USGS Map Sales,
Box 25286, Federal
<br>Center, Bldg 810, Denver CO 80225. The state indexes are free,
maps are
<br>about $4 - 4.50 these days.
<p>-----Original Message-----
<br>From: owner-pittsburgh-railways@dementia.org
<br>[<a href="mailto:owner-pittsburgh-railways@dementia.org">mailto:owner-pittsburgh-railways@dementia.org</a>]On
Behalf Of Kenneth and
<br>Tracie Josephson
<br>Sent: Tuesday, July 11, 2000 5:02 AM
<br>To: pittsburgh-railways@dementia.org
<br>Subject: Re: West Penn Today - We move on!
<p>John Swindler wrote:
<p>> Looking to trace a right of way? Check the 7 1/2 min topo maps
for
<br>streams,
<br>> and that's where to look.
<p>John,
<p>Where can I find these topography maps? Ken J.</blockquote>
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