# corners.txt -- Corners of bounding rectangles for Mahantango wsheds

For the Mahantango watershed, GK27 subwatershed, and WE38 intensive
study area, this file contains

    1.  Corner coordinates of the bounding rectangles;
    2.  Corresponding coordinates of the center of the upper-left pixel
	(grid cell) at various resolutions; and
    3.  Offsets for GK27 and WE38 relative to Mahantango at various
	resolutions.
 
1.  The corners of the bounding rectangles, extended outwards to an
integer multiple of 1000 meters in the UTM projection, zone 18, are as
follows:

 Watershed	      NW corner		      SE corner		Box Size
		 Northing   Easting      Northing   Easting    (N x E, km)

Mahantango	  4512000   335000	  4493000   389000	 19 x 54

GK27		  4511000   356000	  4501000   379000	 10 x 23  

WE38		  4511000   363000	  4506000   367000	  5 x 4



2.  The corners specified above should be used with Arc/Info.  For
gridded data in LAS or ERDAS format, 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
IMAGEGRID and GRIDIMAGE and LAS routines ARC2LAS and LAS2ARC).  To
overlay data at different resolutions, therefore, the LAS/ERDAS upper
left corner coordinates will have different values, as shown below.

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

      1000          4511500.0  335500.0            19 x 54   
                                           
       200          4511900.0  335100.0            95 x 270  
                                           
       100          4511950.0  335050.0           190 x 540  
                                           
        25          4511987.5  335012.5           760 x 2160 
                                           
         5	    4511997.5  335002.5		 3800 x 10800

GK27:
    Pixel Size         Image U. L. C.            Image Size
     (meters)        Northing  Easting      (lines x pixels/line)

      1000          4510500.0  356500.0            10 x 23
                                           
       200          4510900.0  356100.0            50 x 115
                                           
       100          4510950.0  356050.0           100 x 230
                                           
        25          4510987.5  356012.5           400 x 920
                                           
         5          4510997.5  356002.5          2000 x 4600

WE38:
    Pixel Size         Image U. L. C.            Image Size
     (meters)        Northing  Easting      (lines x pixels/line)

      1000          4510500.0  363500.0             5 x 4   
                                           
       200          4510900.0  363100.0            25 x 20  
                                           
       100          4510950.0  363050.0            50 x 40  
                                           
        25          4510987.5  363012.5           200 x 160 
                                           
         5	    4510997.5  363002.5		 1000 x 800



3.  The offsets from images covering the entire Mahantango to images
covering only a subarea will also depend on the image resolution.  These
offsets are given below in the format of a LAS rectangular window
specification (sl,ss,nl,ns), where
    sl = Starting line of window within image (1 denotes first line of
	 image);
    ss = Starting sample (pixel) of window on each image line;
    nl = Number of lines in image window;
    ns = Number of samples (pixels) on each line within window.
Because LAS numbers lines and pixels starting with 1, the actual offsets
from the upper left corner of the larger image to the upper left corner
of smaller image are 1 less than the values of sl and ss given below.

Pixel Size		       LAS Window Specifications
 (meters)	 Maha. to GK27	     Maha. to WE38	 GK27 to WE38

   1000		 (2,22,10,23)          (2,29,5,4)          (1,8,5,4)
                                         
    200		(6,106,50,115)        (6,141,25,20)       (1,36,25,20)
                                         
    100	       (11,211,100,230)      (11,281,50,40)       (1,71,50,40)
                                         
     25	       (41,841,400,920)	    (41,1121,200,160)    (1,281,200,160)
                                         
      5	     (201,4201,2000,4600)  (201,5601,1000,800)  (1,1401,100,800)