[Mapserver-users] ESRI Ascii grid format...

Tue Jun 22 20:49:23 EDT 2004

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It's a bit tricky. You cannot always go on a 'line by line' basis. It tells
you how many values per line, and after that it just dumps the values in
consecutive order. It's for you to decide when to go to the new line (based
on the number of values per line). I think the linefeed comes after a fixed
number of values, irrespective of whether it's reached the end of the data
row yet.

I had a headache with this once, so I wrote a JAVA program to convert it to
XYZ delimited ascii. Just type "java Contour [inputfile] [outputfile]" at
the commandline.

Regards,

Jacob

-----Original Message-----
From: Bruce Raup [mailto:braup at nsidc.org] 
Sent: Wednesday, 23 June 2004 7:19 AM
To: Jason M. Nielsen
Cc: mapserver-users at lists.gis.umn.edu
Subject: Re: [Mapserver-users] ESRI Ascii grid format...

On 2004-06-22 15:13 -0600,  Jason M. Nielsen wrote:

> I have some ascii files dumped as the AAIGRID format from gdal. These
> are esri ascii grids.
>
> The format appears simple:
> ncols        98
> nrows        172
> xllcorner    1044355.808370659710
> yllcorner    10042832.567399607971
> cellsize     91.442854747403
> *then the z values are listed for each line*
>
> Problem is I dont know which friggin way these go. I tried left to
> right starting lower left and incrementing x and y. I end up with 
> skewed data.
>
> Does anyone know where I can get the specs on this format that
> explicitly explain in thorough detail how its formated?

I'm pretty sure the first z-value is the upper-left corner of the grid, and
that it proceeds left-to-right, then down.  I have used GMT (Generic Mapping
Tools (http://gmt.soest.hawaii.edu/)) to handle such files, and had success
using these assumptions.  Sorry, but I don't know where the specs are.

Bruce

-- 
Bruce Raup                                               Phone:
303-492-8814
National Snow and Ice Data Center, U. of Colorado, 449 UCB, Boulder, CO
80309 http://cires.colorado.edu/~braup/
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Content-Type: application/octet-stream;
	name="Contour.java"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: attachment;
	filename="Contour.java"

import java.io.*;
import java.util.*;

public class Contour

{
public static double leftX;
public static double lowY;
public static double rightX;
public static double highY;
public static int numRows;
public static int numCols;
public static String inFile;
public static String outFile;
public static double [][] datagrid;
public static double Xspacing;
public static double Yspacing;

public static void main (String args[])
{

   try
   {

   inFile =3D args[0];
   outFile =3D args[1];
   //leftX =3D Double.parseDouble(args[2]);
   //lowY =3D Double.parseDouble(args[3]);
   //rightX =3D Double.parseDouble(args[4]);
   //highY =3D Double.parseDouble(args[5]);

   readFile();
   writeFile();
   }

   catch (Exception e)
   {
   System.out.println("Usage: \n\n java Contour [inputfile] =
[outputfile] ");
   }

}

public static void readFile ()
{
String readString =3D "";
StringTokenizer token;
String dataOutput =3D "";
String tempNum =3D "";

   try
   {
   RandomAccessFile inputFile =3D new RandomAccessFile (inFile,"r");

   //inputFile.readLine();
System.out.println("opened file");

   readString =3D inputFile.readLine();
   token =3D new StringTokenizer(readString, "\n\r ");
   token.nextToken();
   numCols =3D Integer.parseInt(token.nextToken());

   readString =3D inputFile.readLine();
   token =3D new StringTokenizer(readString, "\n\r ");
   token.nextToken();
   numRows =3D Integer.parseInt(token.nextToken());

System.out.println(numCols);
System.out.println(numRows);

   readString =3D inputFile.readLine();
   token =3D new StringTokenizer(readString, "\n\r ");
   token.nextToken();
   leftX =3D Double.parseDouble(token.nextToken());

   readString =3D inputFile.readLine();
   token =3D new StringTokenizer(readString, "\n\r ");
   token.nextToken();
   lowY =3D Double.parseDouble(token.nextToken());

   readString =3D inputFile.readLine();
   token =3D new StringTokenizer(readString, "\n\r ");
   token.nextToken();
   Xspacing =3D Double.parseDouble(token.nextToken());
   Yspacing =3D Xspacing;

   inputFile.readLine();

rightX =3D leftX + (numCols-1) * Xspacing;
highY =3D lowY + (numRows-1) * Yspacing;

System.out.println(numCols);
System.out.println(numRows);

      while ((readString=3DinputFile.readLine()) !=3D null)
      {
      dataOutput +=3D readString;
      }

   //System.out.println(dataOutput);
   System.out.println(leftX + "\n" + lowY + "\n" + rightX + "\n" + =
highY);

   datagrid =3D new double[numRows][numCols];

   token =3D new StringTokenizer(dataOutput, "\n\r ");

      for (int i =3D 0; i < numRows; i++)
      {
         for (int a =3D 0; a < numCols; a++)
         { =20
         tempNum =3D token.nextToken();
//System.out.println(tempNum);
         datagrid[i][a] =3D Double.parseDouble(tempNum);

//System.out.print(i + ", " + a + "     ");
//System.out.println(datagrid[i][a]);

         }

      }
  =20

   }

   catch (IOException e)
   {
   System.err.println("IO ERROR");
   System.exit(0);
   }
}

public static void writeFile()
{
//double Xspacing;
//double Yspacing;
double Xcord;
double Ycord;

   //Xspacing =3D ((double) rightX - (double) leftX) / (numCols-1);
   //Yspacing =3D ((double) highY - (double) lowY) / (numRows-1);=20

   try
   {
   RandomAccessFile outputFile =3D new RandomAccessFile (outFile, =
"rw");
   outputFile.writeBytes("X,Y,Z\r\n");
      for (int i =3D (numRows-1); i >=3D 0; i--)
      {
         for (int a =3D 0; a < numCols; a++)
         {=20
         Xcord =3D leftX + (Xspacing * (double) a);
         Ycord =3D highY - (Yspacing * (double) i);

         outputFile.writeBytes( (new Double(Xcord)).toString() + ',' + =
(new Double (Ycord)).toString() + ',' + (new =
Double(datagrid[i][a])).toString() + '\r' + '\n');

         }

      }

   }

   catch (IOException e)
   {
   System.err.println("IO ERROR");
   System.exit(0);
   }
}

}
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