comes into play. It’s also called “metadata” and it provides information about how the file is structured. So how many columns and rows are there? You can’t tell just by looking at a file of course – we need header information so we can tell the computer how to break it into rows and columns. We also need to know how the binary data are structured – click on “Data Type” to see that there are a number of options… again, which to pick? The header should help. 3
The header file was one of the files in the zip; its extension is HDR. This is in regular ASCII so you can just open it in notepad. Note Windows might say “can’t recognize the file type”; to remedy this you can just click once on the file, hit F2 and change its extension from HDR to TXT. Then double click and notepad will open it. Or, you can start the notepad program and navigate to the file you want, without changing its extension. Ideally for your own use you should download and use a far superior program called Notepad ++. Here we see that in fact we do only have one band. We also see that we have 1731 rows and 1010 columns. Rows run horizontally and are numbered up the side, so “Y” if you think of a Cartesian plot, and so Columns are oriented vertically across the top, so “X” on a Cartesian plot. In terms of data type, it says “NBITS”=16 – see below that one byte is 8bits, so 16 bits is two bytes. I’m going to let you make some mistakes so you can get a better feel for the controls and manipulations needed for these sorts of files. Tell it where your BIL file is and enter the values for the X and Y Cell Counts. Enter “m” for units because the data are meters. Finally go to “Data Type” and select “2-byte integer (unsigned)”. Unsigned means we expect all values to be positive. Don’t change the other parameters for now. It should look like the screenshot below. Tell it to execute the import by clicking Okay on the right side.
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- Fall '18
- Filename extension, Computer file, Computer program, Byte, Plain text