| Knowledgebase Home | Contact |
 Search the Knowledgebase |
 Browse by Category |
| How can I calculate the volume and/or area inside an irregular polygon? | |||||||||
If you want to calculate the volume or surface area inside a polygon, blank the grid file outside the polygon defining the area using Grid | Blank, and then use the Grid | Volume command. The blanked areas are not included in the volume calculations and are separated out in the surface area calculations. Step 1: Blank the Grid File to the Desired Area The area outside the desired polygon area can be blanked using a BLN file that describes the boundary of the polygon. Grid the data over the entire rectangular bounding box and blank the area inside or outside a polygon defined in an text BLN file. If you need help creating a BLN file, please see instructions on how to create a BLN file. Once the BLN file is created, be sure to open the BLN file in the Surfer worksheet and confirm that cell B1 shows a 0 (zero), which tells Surfer to blank outside the polygon in the BLN file. If it is a 1, change it to a 0, save and close the file. Then use the Grid | Blank command, select the grid file and click Open, select the BLN file and click Open, and save the blanked grid to a new name. Step 2: Calculate the Volume and Area Once the grid is blanked, so that there is only data inside the area you want (you may want to create a contour map first to confirm this): 1. Go to Grid | Volume. 2. Select the grid file and click Open. 3. In the Grid Volume dialog, the grid file will be entered as the Upper Surface. The volume calculations calculate the volume between two surfaces. You can calculate between a grid file and a horiztonal surface, or between two grid files. Enter your desired input for the Upper Surface and Lower Surface and click OK. 4. The Volume Report is generated. The volume calculations will not include the areas that are blanked. The units of the volume are in X*Y*Z. If your X, Y and Z data are all in meters, then the volume is reported in m^3 (and surface area is X*Y, or m^2). See Also: How can I create a BLN file? How can I grid only the area inside my data limits? How can I create a map inside an irregular boundary? |
| Visitor Comments |
| No visitor comments posted. Post a comment |
| Attachments |
| No attachments were found. |
Print this page
Email this page
Post a comment
