USGS maps and aerial photos for PA

[Jim Holland]

Greetings!

Derrick J Brashear wrote:

> Now that I typed it I see it's a big wordy, and I'm sorry about that.

	Not at all wordy but definitely informative.
	I know that the printed maps are usually 20+ years old; do you know the
dates for these current maps?  I would prefer 1950 myself (but as padre
always said: "beggars can't be choosy!")!  And I would definitely be
interested in a CD and look forward to more information!

> The Pennsylvania Spatial Data Access system is hosted at the Deasy
> Geographics Lab at Penn State. Their home site is http://www.pasda.psu.edu
> and they have an archive with includes all 7.5' series quadrangles for PA,
> both collared and collarless, and all of the aerial photo quadrangle
> quadrants (a.k.a. USGS DOQs)
> 
> Quadrangle maps can be found in
> ftp://penne.deasy.psu.edu/pub/pasda/drg24k
> and versions of these with collars clipped in
> ftp://penne.deasy.psu.edu/pub/pasda/drg24k-c
> 
> The files are zip files named for the quadrangle contained therein, e.g.
> lancaster_pa.zip. Unzipping the file will give you generally a .tif file
> and a .tfw file. Some may also have a .met or .mgd file, which are
> metadata (like the date of the quadrangle). The .tif file is a TIFF image
> file with GeoTIFF tags added. The GeoTIFF tags are essentially
> georeferencing information, sufficient such that a suitably equipped piece
> of software can know the coordinates of any point in the image.
> 
> For Windows users (of which I am not one) I know of at least 2 free data
> viewers which can handle this information (note that any TIFF viewer can
> be used if you don't care about the georeferencing, and since TIFF is a
> standard format your Windows system might come with a viewer. I don't
> know)
> 
> http://mcmcweb.er.usgs.gov/viewers/dlg_view.html is the USGS's map viewer
> software.
> 
> http://www.esri.com/software/arcexplorer/index.html is from ESRI, the
> largest GIS software maker probably in the world.
> 
> The latter package is probably more refined.
> 
> The latter package can also be used to view all of the aerial photos. They
> come in 3 formats. One is the aforementioned .tif/.tfw style. The other 2
> are ESRI "proprietary" formats, called .bil and .bsq (band interleaved by
> line and band sequential). .bil and .bsq files come with a .hdr file with
> some header information in it.
> 
> The aerial photos can be found at
> ftp://penne.deasy.psu.edu/pub/pasda/doq
> 
> The files are again zip files, this time named by a quadrant of a 7.5'
> quadrangle, e.g. lancaster_pa_nw.zip. They will contain either a .tif/.tfw
> pair or a .hdr file with a .bil or a .bsq file.
> 
> The resolution of the 7.5' quadrangles is 1 pixel equal to about 2.1
> meters squared. The resolution of the DOQs is 1 pixel equal to 1 meter
> squared.
> 
> I expect to be able to burn custom CDs of these in the future, as I'm am
> about 3/4 of the way through having a complete set of DOQs downloaded, and
> I already have virtually all of the mid-Atlantic region's 7.5' quadrangles
> downloaded. With non-standard TIFF "deflate" compression a DOQ file is
> about 30 megs, meaning about 14 can be fit on a CD, or the equivalent of 3
> and a half 7.5' quadrangles worth. When I get to the point where I have
> all the maps and can burn CDs useable under Windows I will mention it to
> the list, and can hopefully make up CDs for those of you who have some pet
> area you're after. Oh, and I'll have to provide a TIFF inflator for you.
> 
> Theoretically this means that all of West Penn coke region territory could
> be covered on 2 cds. I intend to try it. Note though, that even with 1m x
> 1m resolution it's not obvious from the air where the main line ran after
> leaving 119 before it reached the street again in Dunbar (which is to
> say, the stretch where it crossed the PRR, B&O and WM in short order)
> 
> Must of the same data is available from the Microsoft Terraserver
> (http://terraserver.microsoft.com), but they don't yet cover all of PA
> last I checked, their data is tiled into small JPGs, which means if you
> want a large area you either have to capture an image or paste them
> together, and at least one of the satellites they got source image data
> from seems to have been a bit wacky when it passed near my house and
> potentially elsewhere: a nearby corner doesn't mate nicely.
> 
> Note that all USGS data is freely redistributable, since your tax dollars
> bought it.
> 
> You can send me any questions you have on the subject; As you might have
> guessed this is an area of personal interest to me;-)
> 
> -D

James B. Holland
------- -- ---------
        Pittsburgh Railways Company (PRCo), June of 1949 -- June of 1953
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