![](media/image1.png)NOAA NESDIS

**Center for Satellite Applications and Research (STAR)**

GVI-x Vegetation Health Product

User Guide

Version 0.2\
Sep. 2, 2008

![](media/image2.png)

**Prepared by I. M. Systems Group, Inc.**

**Mr. Wei Guo (<Wei.Guo@noaa.gov>)**

**Contents**

1\. Introduction 2

2 File name convention 2

3 File attributes 3

4 Scientific dataset 4

**1. Introduction**

This document describes the data format of GVI-x derived Vegetation
Health Indices Product (GVI-x VH).

GVI-x VH was generated by CGVPS.exe (a C++ program developed by
<Wei.Guo@noaa.gov>). The input of this software is GVI-x product (weekly
composite re-processed GVI in HDF format), output are GVI-x VH products
which contain the following variables:

Table 1 variables of GVI-x VH products

  -------------- --------------------------------------------------------
  Data type      content

  NVI            NDVI ,

  SMN            Smoothed NDVI,

  VCI            Vegetation Condition Index,

  BT4            Brightness Temperature,

  SMT            Smoothed Brightness Temperature,

  TCI            Temperature Condition Index

  VTI            Vegetation Health Index

  MXN            Climatology: Maximum NDVI ;

  MNN            Climatology: Minimum NDVI ;

  MXT            Climatology: Maximum Brightness Temperature.

  MNT            Climatology: Minimum Brightness Temperature.
  -------------- --------------------------------------------------------

The GVI-x VH products are self-explained HDF files. Each file

Contain one of above variable.

**2. File name convention**

**Example: GVIX_NN_G16_C07_VTI_Y2006_P39.hdf**

**Format: GVIX_xx.Grr.Ccc.typ.Pyyyy_Ppp.hdf**

**where,**

+--------+--------------------------------------------------------------+
| GVIX   | Prefix of the file name;                                     |
+--------+--------------------------------------------------------------+
| xx     | Satellite ID, example:                                       |
|        |                                                              |
|        | NC -- NOAA 7                                                 |
|        |                                                              |
|        | NF -- NOAA 9                                                 |
|        |                                                              |
|        | NH -- NOOA 11                                                |
|        |                                                              |
|        | NJ -- NOAA 14                                                |
|        |                                                              |
|        | NL -- NOAA 16                                                |
|        |                                                              |
|        | NN -- NOAA 18                                                |
+--------+--------------------------------------------------------------+
| rr     | Resolution in km                                             |
+--------+--------------------------------------------------------------+
| cc     | two-digits, number of days per composite period;             |
+--------+--------------------------------------------------------------+
| typ    | Data type, see table 1                                       |
+--------+--------------------------------------------------------------+
| yyyy   | four-digits, year number of the processed period;            |
+--------+--------------------------------------------------------------+
| pp     | Two-digits, period number;                                   |
+--------+--------------------------------------------------------------+

**3. File Attributes**

GVI-x VH product contains the following file attributes (Meta data)
(table 2). They provide general information about the product.

Table 2 Description of File attributes (Meta data)

  ----------------------- ------------------------------------------------
  Meta data tag           Content

  GRID_ROWS               Number of rows for data grid

  GRID_COLUMNS            Number of columns for data grid

  START_LATITUDE_RANGE    The latitude of the grid's northern edge

  END_LATITUDE_RANGE      The latitude of the grid's southern edge

  START_LONGITUDE_RANGE   The longitude of the grid's western edge

  END_LONGITUDE_RANGE     The longitude of the grid's eastern edge

  PROJECTION              Projection type

                          

  [(the following is      
  optional, may not       
  appear in file)]{.mark} 

  FILENAME                File name of the product file

  SATELLITE               Satellite ID, for example, NN for NOAA-18

  YEAR                    Year of the composite period

  PERIOD_OF_YEAR          Number of the composite period

  DAYS_PER_PERIOD         Number of days per period
  ----------------------- ------------------------------------------------

**4. Scientific dataset**

The variable in the GVI-x VH product file is saved as scaled 16-bits
integers. The scaling parameters are attached to the scientific dataset
(SD) as attributes. To convert scaled data to non-scaled physical
values, the following formula should be used:

Physical_value = (RANGE_MAX *−* RANGE_MIN) / (SCALED_MAX *−* SCALED_MIN)

\*(scaled_value *−* SCALED_MIN) + RANGE_MIN

Table 3 Description of SDS attributes for GVI-x VH variables.

  ------------------- ---------------------------------------------------
  Attribute name      Description

  UNITS               Units of the variable data.

  MISSING             Value in the variable data indicating missing
                      elements.

  SCALED              Non-zero if variable data was scaled.

  RANGE_MIN           Minimal data physical value.

  RANGE_MAX           Maximal data physical value.

                      

  If SCALED is        
  non-zero, the       
  following tags are  
  also present:       

  SCALED_MISSING      MISSING's counterpart for scaled data values.

  SCALED_MIN          Minimal value of scaled data

  SCALED_MAX          Maximal value of scaled data
  ------------------- ---------------------------------------------------

(End)