Acquiring  GIS  Data: Utah

Ohio codes (1:24k quadrangles):

Ohio codes breakdown a 1x1-degree grid block into a smaller grid system known as 7-1/2’ quadrangle.  The Ohio code values are derived from the latitude and longitude of the SE corner of the 1x1 degree block and an assigned grid number.  The grid system starts in the lower right hand corner of each 1-degree grid block and uses the latitude and longitude as a prefix to a 64 grid section.

Results: ( ohio_codes_a1-h8 ) ,

For example, in the image above, the 37 degree latitude line and the 112 degree longitude line are concatenated to form 37112.  In addition to the latitude and longitude, a two character grid number is assigned to each 7-1/2 minute section, starting from right to left and bottom to top.  Right to left use 1-8 and bottom to top use A-H. 

Thus the first 7-1/2 minute quadrangle of this example would be 37112A1, in the bottom right hand corner and the last ending with 37112H8 in the upper left hand corner.  

64 7-1/2 minute quadrangles are created with this grid system.  These values become critical when searching for data and when you need to download the files.  We will be using this in later exercises when we work with Digital Elevation Models (DEM).

Questions:

Give the Ohio code names of the surrounding quadrants of 37112E5.

Give the Ohio code names of the surrounding quadrants of 37112H8.

How many grids/quads make up the 1x1 degree block?

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