Using GTOPO30 DATA in ArcGIS

To have a seamless integration of data (tiles in gtopo30)in ArcGIS, the following steps should be done:

1. Uncompress the TAR file using WinZip 6.2 or higher.
2. Change the *.dem extension to *.bil.
3. Open ArcCatalog.
4. Navigate to the *.bil created in Step 2.

5. Right-click on the *.bil, click Export, and click the Raster to Different Format option. Specify the location to which you will save the new grid, and ensure the Save As Type is set to ESRI GRID.

6. Open ArcMap and add the grid created in Step 5.

7. On the ArcGIS Spatial Analyst toolbar, click Spatial Analyst and select Options.
8. Click the General tab and set the working directory.

9. Click the Extent tab and set the analysis extents to Same as layer 'your grid'. ( It is based on the extend that you are looking for: indicate specified region)

10. Click the Cell Size tab and set the cell size to Same as layer 'your grid'. Click OK.

11. Navigate to ArcGIS Spatial Analyst and select the Raster Calculator. Enter the following expression, substituting your grid for [in_grid]. Include the square brackets.

12. CON([in_grid] >= 32768,[in_grid] - 65536,[in_grid]
13. Click Evaluate.

14. The ocean areas (-9999) can be converted to NODATA using the SETNULL function. Insert the Calculation from Step 11 for [Calculation]. Include the square brackets.

15. setnull([Calculation ] == -9999, [Calculation ])

16. Be aware at the end you should export the Calculation data by right click on the table od the content (The format of saving data should be Grid).