AmeriGEOSS GNC-A Workshop 7-10 June 2016, Colombia

Transcription

1 AmeriGEOSS GNC-A Workshop 7-10 June 2016, Colombia McIDAS-V Tutorial 5: Normalize Difference Vegetation Index (NDVI)

2 Contents 1. Getting Started Changing the Default Background Map Loading the NOAA NDVI AVHRR GeoTIFF File Loading the INPE NDVI GeoTIFF File produced from VIIRS imagery Getting Started McIDAS-V McIDAS-V is a visualization and data analysis software package. This tutorial assumes that you have limited experience with McIDAS-V. For a list of references, the following online documentation page includes a current user s guide, tutorials and instructional videos: Tutorial Files Download and save the provided files. The NDVI_AVHRR directory contains weekly AVHRR normalized difference vegetation index (NDVI) data, 1 file for every 4 th week. Note that the GNCA_June2016.jar file should already be installed. If this is not the case, please refer to McIDAS-V Tutorial 1. NDVI_AVHRR (14 files) NDVI from INPE via GNC-A McIDAS-V Tutorial 5: NDVI 1

3 2. Changing the Default Background Map 2.1 Open McIDAS-V. Recall that the two main windows are: Data Explorer where data is selected and layer properties are modified Main Display Window shows a map projection and any selected data 2.2 You can change the background map settings to your preference at any time (refer to McIDAS-V Tutorial 1). A good start is to zoom in on the Caribbean region. If you did not save this as your default setting, go to the Main Display window and select Projections Predefined Caribbean. You may also change the map outline by clicking Default Background Maps and making your changes in the Layer Controls panel. McIDAS-V Tutorial 5: NDVI 2

4 3. Loading the NOAA NDVI AVHRR GeoTIFF File 3.1 These NDVI products mask for clouds. These files are in a GeoTIFF file format. Pull up the Data Sources tab. a) In the column on the left expand the General heading. Then select Files/Directories. b) From the Data Type menu, select TIFF files. c) From the Look In menu, navigate to the directory where you have saved the NDVI AVHRR files. Here (D:\GNCA\data\NDVI_AVHRR) d) Select a file of your choice. The last three digits in the filename correspond to the week number in In this example we will use VHP.GO4.C07.NP.P SM.SMN.tif, which corresponds to 26 Jan 1 Feb e) Click the Add Source button. b c a d e 3.2 Create an image display of the NDVI data. Click on the Field Selector tab. a) Under the Data Sources column, select the GeoTIFF filename. b) Under the Fields column, select VHP.GO4.C07.NP.P SM.SMN.tif Grid data. c) Under the Displays column, select Image Display. d) Click the Create Display button. McIDAS-V Tutorial 5: NDVI 3

5 a b d c 3.3 Change the display properties under Layer Controls. a) Click the color table button and select GNCA NDVI_black. Change the range from 0 to 0.7. b) Add the color table to the display image by selecting Edit Properties and making your changes b on the Color Scale tab. Click Apply/OK c) To change the layer and legend labels, select Edit Properties and make your changes in the Settings tab. Click Apply 3.4 View the data in the Main Display window and zoom in on Guyana or some other location.? Is vegetation uniform or variable across the region? 3.5 Let s load another file to see how vegetation changes throughout the year. Pull up the Data Sources tab. a) In the column on the left expand the General heading. Then select Files/Directories. McIDAS-V Tutorial 5: NDVI 4

6 b) From the Data Type menu, select TIFF files. c) From the Look In menu, navigate to the directory where you have saved the files. d) Select a different file than last time. In this example we will use VHP.GO4.C07.NP.P SM.SMN.tif, which corresponds to July e) Click the Add Source button. 3.6 Create an image display of the NDVI data. Click on the Field Selector tab. a) Under the Data Sources column, select the GeoTIFF filename. b) Under the Fields column, select VHP.GO4.C07.NP.P SM.SMN.tif Grid data. c) Under the Displays column, select Image Display. d) Click the Create Display button. 3.7 View the data in the Main Display window and zoom in on Guyana or some other location. Compare and contrast NDVI for January and July. Is there a seasonal change? How does this relate to precipitation? McIDAS-V Tutorial 5: NDVI 5

7 4. Loading the INPE NDVI GeoTIFF File produced from VIIRS imagery Load a different format GeoTIFF produced by INPE and available through GNC-A. The values in this file need to be divided by 255, so a formula will be applied. 4.1 Pull up the Data Sources tab. a) In the column on the left expand the General heading. Then select Files/Directories. b) From the Data Type menu, select TIFF files. c) From the Look In menu, navigate to the directory where you have saved the NDVI AVHRR files. Here (D:\GNCA\data\NDVI_INPE) d) Select INPE_NDVIM_ tif. e) Click the Add Source button. 4.2 Click on the Field Selector tab. a) Under the Data Sources column, select Formulas. b) Under the Fields column, expand the GeoTIFF Tools June 2016 and select NVDI from INPE. c) Under the Displays column, select Image Display. d) Click the Create Display button and a new Field Selector window will appear. e) Expand INPE_NDVIM_ tif and select INPE_NDVIM_ tif Grid data. Click OK. McIDAS-V Tutorial 5: NDVI 6

8 4.3 Change the display properties under Layer Controls. a) Click the color table button and select GNCA NDVI_black. Change the range from 0 to 0.7. b) Add the color table to the display image by selecting Edit Properties and making your changes b on the Color Scale tab. Click Apply/OK c) To change the layer and legend labels, select Edit Properties and make your changes in the Settings tab. Click Apply McIDAS-V Tutorial 5: NDVI 7

9 The NOAA AVHRR NDVI data was downloaded from this site: ftp://ftp.star.nesdis.noaa.gov/pub/corp/scsb/wguo/data/vhp_4km/geo_tiff/ More information can be found in the NDVI quick guide. The INPE NDVI files are broadcast through GNC-A. How can you use this data set combined with precipitation and surface temperature to monitor drought? Would you like to see both of these data sets on GNC-A? McIDAS-V Tutorial 5: NDVI 8