Creating a multispectral service using the NDVI process

Satellite images are often used to measure and display the density of plant biomass over the entire globe. One common measurement is called the Normalized Difference Vegetation Index (NDVI). This index uses the contrast of characteristics of two bands in a multispectral raster dataset—the chlorophyll pigment absorptions in the red band and the high reflection capability of plant materials in the near-infrared band.

To create an NDVI image service definition, you need to have a raster dataset containing the red and near infrared bands. You then apply the NDVI process to the image service definition. You also use the Colormap process to apply color to the results of the NDVI in the displayed image service definition.

Learn more about the NDVI process

To create an NDVI image service definition, the input image should be multispectral, containing one red band and one infrared band.

手順:

1. Open ArcMap.
2. Click the Image Service drop-down menu on the Image Service Definition Editor toolbar and click Advanced → New Service Definition.
3. Type the correct path and name in the Service definition text box, or click the browse button to navigate to the location and provide a name.
4. Click the Spatial reference browse button and choose a spatial reference file for either a geographic or projected coordinate system.
5. Click the Service type drop-down arrow and click Color (RGB).
6. Click OK to create the new image service definition.

   The new image service definition is added to the table of contents as a customized group layer.

7. Click the Image Service drop-down menu on the Image Service Definition Editor toolbar and click Advanced → Add Raster Dataset.

   The Select Raster Type dialog box appears.

8. Add a multispectral image to the service.

   Make sure that you remember which band number you associated each input location with. For example, if using a Landsat scene, Input for Band 1 would be Band 3 (the red band) and Input for Band 2 would be Band 4 (the near-infrared band).

   You can uncheck the pan-sharpening option. You also don't need to apply any enhancement or sharpening.

9. Click the Image Service Properties button on the Image Service Definition Editor toolbar.

   The Image Service Properties dialog box appears.

10. Click the Service Processes node.
11. Add the NDVI process.

    Learn how to apply a process on an image service definition

12. Click the Edit button to change the required process parameters.

    The NDVI Process Definition dialog box is displayed.

13. Type the number of the input that represents the red band in the text box.

    For example, based on the information in step 8, this would be 1.

14. Type the number of the input that represents the near-infrared band in the text box.

    For example, based on the information in step 8, this would be 2.

15. Type 50 in theNDVI Offset text box.
16. Type 1 in the NDVI Scale text box.
17. Click OK. The NDVI service is ready.

    You can now apply the Colormap process to this NDVI image service so the image data will be displayed as an RGB image.

18. Add the Colormap process.

    The Color Map Process Definition dialog box is displayed.

19. Click the Color table source browse button to navigate to a color table source.

    The color table source can be an .act file or a .clr file.

    Learn how to create a .clr file

20. Click OK to close the Color Map Process Definition dialog box.
21. Click OK to close the Image Service Properties dialog box.

    Make sure the processes are still checked on before closing the dialog box.

22. Click the Image Service drop-down menu on the Image Service Definition Editor toolbar and click Advanced → Build.

    The Build Options dialog box is displayed.

23. Click OK.
24. Once the process is complete, click the Image Service drop-down menu on the Image Service Definition Editor toolbar and click Advanced → Overviews → Optimize Service → Define.
25. Click OK to accept the defaults.
26. Click OK on the message box letting you know the service overviews have been defined.
27. Click the Image Service drop-down menu on the Image Service Definition Editor toolbar and click Advanced → Build.
28. Make sure Generate derived images is checked.

    By default, Compile service is checked. The Generate derived images operation creates the service overviews you've defined.

29. Click OK.

    The image service is first compiled, then the service overviews are generated. Once this is complete, you can preview and publish the image service.