West Branch Susquehanna River above Williamsport:
corners of bounding rectangle

The drainage basin for the segment of the West Branch of the Susquehanna River above the Williamsport flow gage station is located in north-central Pennsylvania, covering the northwestern part of the Susquehanna River Basin. To facilitate assembling a set of co-registered datasets containing land surface characteristics and model outputs for this basin, a rectangular box has been defined which encloses the entire drainage basin, with boundaries extended outwards to an exact multiple of 1 km in the Albers equal area projection used for Pennsylvania.

The boundaries and dimensions of the box are as follows:

                                                           Dimensions 
                     Min X   Max X     Max Y   Min Y      E-W      N-S

  Albers Equal      -80000   110000   321000   151000    190000   170000
   Area Projection     (easting)         (northing)

  Approximate        -79.0    -76.7     41.9    40.3       2.3      1.6
    Lat/Long           (longitude)        (latitude)

The northwest corner of this box is at the same easting as the box defined for the entire Susquehanna River Basin; its northing is 129 km less. For images and data layers gridded at 1 km, the box enclosing the West Branch above Williamsport extends from line (row) 130, sample (column) 1 of the SRB box through line 299, sample 190.

The corners specified above should be used with GIS software packages such as Arc/Info. For gridded data used with image processing packages such as LAS or ERDAS, the coordinates of the upper left corner of the image specified by the LAS .ddr file or in the ERDAS header record refer to the CENTER of the upper left pixel; i.e., they are offset by one-half pixel from the corner of the bounding rectangle (the necessary adjustments are made automatically by Arc routines such as IMAGEGRID and GRIDIMAGE). To overlay data at different resolutions, therefore, the LAS/ERDAS upper left corner easting should be increased by one-half the grid cell size, and the northing decreased by one-half the grid cell size. For the lower right corner, the easting should be decreased by one-half the grid-cell size and the northing increased by the same amount. For the pixel (grid) dimensions commonly used for SRB data sets, this yields the pixel-center coordinates at the upper left and lower right corners and the image dimensions which are given below.

Pixel Size     Image U. L. C.      Image L. R. C.         Image Size
 (meters)    Northing  Easting   Northing  Easting  (lines x pixels/line)

   1000       320500   -79500     151500   109500         170 x 190

    100       320950   -79950     151050   109950        1700 x 1900

Projection Parameters

Albers Equal Area Conic

This projection, which is centered on Pennsylvania, has been used extensively for a number of datasets covering all or part of the state. 

	Projection units:	meters
	Spheroid:		Clarke 1866
	1st standard parallel:  40.0° N
	2nd standard parallel:	42.0° N
	Central meridian:	-78.0° (W)
	Latitude of origin:	39° N
	False easting:		0
	False northing:		0

Last change: 1998 Mar. 13, R. A. White / raw@essc.psu.edu