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Surfer 6 Grid File Format

Surfer 6 grid files [.GRD] use a layout similar to the ASCII grid format. The only difference is in the identification string and that Surfer 6 grid files are binary.

Data types used in Surfer 6 grid files include:

Type

Description

char

single byte

short

16 bit signed integer

float

32 bit single precision floating point value

double

64 bit double precision floating point value

The Surfer 6 format has the following layout (byte position is base 1):

Element

Byte Pos.

Type

Description

id

1,2,3,4

char

4 byte identification string DSBB which identifies the file as a Surfer 6 binary grid file.

nx

5

short

number of grid lines along the X axis (columns)

ny

7

short

number of grid lines along the Y axis (rows)

xlo

9

double

minimum X value of the grid

xhi

17

double

maximum X value of the grid

ylo

25

double

minimum Y value of the grid

yhi

33

double

maximum Y value of the grid

zlo

41

double

minimum Z value of the grid

zhi

49

double

maximum Z value of the grid

z1, z2 ...

57, 61...

(step 4 bytes to end of file)....

float

Grid data. First value is the lower left node, and the subsequent nodes procede across the row until the end, then up to the second row, etc., until finishing at the upper right node.

Sample Code

Use the example table to determine what data type you should use for each header value. For example, if you want to get the xMin value of the grid in Scripter, you would insert the following code:

Dim xMin As Double

Open [your filename] For Binary As #1

Get #1,9,xMin

Close #1

Or, if you wanted to load all of the data into an array, you would use this:

Dim xCols As Integer

Dim yRows As Integer

Dim myData() As Single

Open [your filename] For Binary As #1

Get #1,5,xCols

Get #1,7,yRows

ReDim myData((CLng(xCols) * CLng(yRows)) -1)

Get #1,57,myData

Close #1

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