Advanced Import can also import DEM files and provide DEM schema settings. In this exercise you’ll also specify coordinates to create a crop of the image. To learn more about cropping just an image, see the GeoCrop Tutorial.
1.On the Geographic Imager panel, click the Advanced Import button.
2.On the Advanced Import dialog box, choose USGS DEM from the Format drop-down list and click Browse.
3.Navigate to the \Tutorial Data\Mt Olympus 3D Landscape Data folder, choose MtOlympus.dem, and click Open.
The Mount Olympus DEM is displayed in the Image Sources list and shows that it has a NAD83 / UTM zone 10N coordinate system and an 1024 x 1449 pixel image dimension. If the DEM Schema is not listed as Auto-stretched, click the schema hyperlink and choose the Auto-stretched schema. This will help the DEM to be displayed using a colour ramp that is auto-stretched to it's values.
4.Double-click the MtOlympus.dem image source.
5.In the Image Extents section, click the Crop Image button.
6.In the GeoCrop dialog box, click the Crop by Extents button.
7.Choose WGS 84 from the Use drop-down list and choose Decimal degrees from the Format drop-down list.
8.Under Minimum, enter 47.762 into the Lat box and enter -123.743 into the Long box.
9.Under Maximum, enter 47.790 into the Lat box and enter -123.698 into the Long box.
10. Click OK. Click OK again to close the GeoCrop dialog box.
The image dimensions are now 681 x 630 pixels (cropped from 1024 x 1449 pixels) according to the crop coordinates you specified. The DEM Schema also changes to "Crop auto-stretched" to indicate that not all of the values in the DEM are included in the schema.
11. You’ll save the DEM Schema so that it has a proper name and so you can see its range values.
12. In the DEM Schema section, click the Crop-autostretched hyperlink.
13. In the Import DEM File dialog box, click the green Create New Schema button. Enter Rocky Mountains Cropped as the new schema name, then click OK.
The elevation range values for the cropped image are 861 meters (lowest) to 2006 meters (highest).
14. Click OK to close the dialog box.
In the Image Sources list, the MtOlympus.dem is updated showing adjusted range values and image dimensions.
15. Click OK to import the DEM.