If you have a data file that already contains gridded data, the following header can be placed in the file and the file directly imported into SURFER:

id                  the code letters DSAA which identify the file as an ASCII grid file.
                     (note: DSAA must be in caps)
nx   ny           nx (integer) is the # of grid lines along the x axis (columns)
                     ny (integer) is the # of grid lines along the y axis (rows)
xlo   xhi        xlo min. x value of the grid
                     xhi max. x value of the grid
ylo   yhi        ylo min. y value of the grid
                     yhi max. y value of the grid
zlo   zhi        zlo min. z value of the grid
                    zhi max. z value of the grid
grid row 1 z data.............................................
grid row 2 z data.............................................
etc.

these are the z values of the grid, organized in row order. The grid row 1 corresponds to ylo and the last to yhi. (This means that the first line corresponds to the “south” end of the map). As long as the grid values in the file are ordered correctly from left to right, it does not matter how many entries there are per line. Thus, you can put a grid row on one or more lines, as long as the values are ordered consecutively.
 

For an example of the header, say you have generated a grid containing 11 rows and 6 columns. Edit the file by typing in the first five lines as described above (shown in bold italics):

DSAA
6  11
0  500
0  1000
100.0  104.0
100.0       100.9       101.3       101.5       101.6       101.5
100.9       101.3       101.5       101.7       101.8       101.8
101.6       101.7       101.9       102.0       102.0       102.0
102.1       102.1       102.2       102.3       102.3       102.3
102.5       102.5       102.6       102.6       102.6       102.6
102.8       102.9       103.2       102.9       102.8       102.8
103.0       103.1       103.2       103.1       103.1       103.0
103.2       103.2       103.3       103.2       103.2       103.2
103.4       103.4       103.4       103.4       103.4       103.4
103.5       103.5       103.5       103.5       103.6       103.7
103.6       103.7       103.6       103.6       103.7       104.0

download the file: example.grd

Save the file on disk. Next, once in SURFER, click on “MAP” and then “CONTOUR.”  Find the file with the browse button and click OK. The next window will let you select the way you want to style your map. Click OK and the contour map should appear on the screen.

Note: you will probably want your grid to be mapped so that the first line of the file will be the “north” row and the last line the “south” row. The row order can be reversed in the file editor or you can do this directly in SURFER (version 6 or higher). Choose GRID and then TRANSFORM. Select your grid file and then choose “Mirror Y” as the operation. The new file (by default called “OUT.GRD”) will be oriented properly and can then be contoured as needed. Here is the map using default SURFER's default parameters: