Center for Earth Observation

...supporting the remote sensing needs of the University

What kinds of MODIS data are available?

MODIS data can be placed in two broad categories; daily scenes and derived products. You can order a daily scene for any specific date and location; and at different times of day and night as mentioned above.

Many consolidated products have been developed from MODIS data.  These include 8‑day and 16‑day composite images, a variety of indices, and a range of global products with varying time scales.  Products are separated into four science discipline groups. Data for each group may be obtained from specific sites and have unique import techniques described below.  You can learn about each group at the following sites:
 

Next you need to decide where and when you want data coverage.  Locations for full daily scenes and products can be entered using latitude and longitude.  If you do not know this information, you could use sites such as Google Earth to locate your area of interest and read the coordinates displayed on the screen.  Level 2 processed MODIS data such as the Surface Reflectance products are segmented into tiles with an area of 10º X 10º using a sinusoidal projection.  Level 3 products are “gridded” into global datasets.

Dates are in the Julian format, i.e. yyyyddd.  There is a Julian Date Converter program on the desktops of the YCEO workstations.  Time is in Universal Time Coordinated (UTC).  The data are provided in the HDF-EOS format.

Daily MODIS Scenes – Level 1

Individual daily MODIS scenes, MODIS Level 1 products, can be obtained for any part of the earth, every day, since February 2000.  These files are in the Geographic projection.  A complete dataset has a spatial resolution of 1 km and there are 36 bands of data.  The data are distributed as digital numbers in 16 bit unsigned integer format.  These data should be converted to radiance values, surface reflectance values, and/or brightness/temperature values before performing any analysis.

Terra file names for a complete file begin with MOD021KM.  Aqua file names begin with MYD021KM.  The product name on the MODIS ordering site is:

 “MODIS/Terra Calibrated Radiances 5-Min L1B Swath 1KM V005”. 

In addition you can obtain daily scenes at higher spatial, but lower spectral, resolution.  Files with 500m resolution contain the 7 bands of data in the Visible, Near-IR and Mid-IR parts of the spectrum.  Files with 250m resolution contain two bands of data in the Red and Near-IR parts of the spectrum.   The Terra names for these are MOD02HKM and MOD02QKM respectively.

MODIS Products - Level 2

As mentioned earlier, many products have been developed from MODIS data.  You should read the product descriptions for each product you intend to use.  This will provide information about data range, scaling values, fill values, data type and format, etc.  Product data are generally provided in the sinusoidal projection.  Below are short descriptions of the surface reflectance and vegetation products.  Many more products are available.  While the information below is accurate at the time of writing, you should always read the online USGS metadata for any product you plan to work with.

MODIS Products - Level 3

These MODIS data are gridded into global datasets.  You can search for these data at the same sites that MODIS Level 2 products are distributed.

Surface Reflectance Products

The surface reflectance products are generated from the first two, or seven, bands of the corresponding full 36 band scenes.  These provide an estimated “at surface” spectral reflectance.  Several algorithms are applied to various MODIS bands to remove the effects of cirrus clouds, water vapor, aerosols and atmospheric gases.  Global surface reflectance products can be obtained at either 250m with 2 bands or 500m with 7 bands, as daily or 8-day composite images.

The data type is 16 bit signed integer, which has a theoretical range of values from -32,768 to +32,768.  The documented data range is from -100 to +16000 with a fill value of -28,672.  If you wish to convert these numbers to a valid reflectance data range, cell values should be divided by 10,000.  These data must then be stored with a floating point data type.

The data are provided in the HDF-EOS format.  MODIS data at version 4 and above use the Sinusoidal projection with the WGS84 datum.  A very small sample of common products are listed below.

MOD09GQ - MODIS Surface Reflectance Daily L2G Global 250m

This file has a spatial resolution of 250 m and contains two bands of spectral data centered at 645 nm and 858 nm.  There are also three bands of additional information on band quality, orbit and coverage, and number of observations.

MOD09GA - MODIS Surface Reflectance Daily L2G Global 500m

This file has a spatial resolution of 500 m and contains seven bands of spectral data plus three bands of additional information on band quality, orbit and coverage, and number of observations.  The spectral range for each band can be found in Appendix A, bands 1 through 7.

MOD09Q1 - MODIS Surface Reflectance 8-Day L3 Global 250m

This file is a composite using eight consecutive daily 250 m images.  The “best” observation during each eight day period, for every cell in the image, is retained.  This helps reduce or eliminate clouds from a scene.  The file contains the same spectral information as the daily file listed above, centered at 645 nm and 858 nm.  There is one additional band of data for quality control.

MOD09A1 - MODIS Surface Reflectance 8-Day L3 Global 500m

This file is a composite using eight consecutive daily 500 m images.  The “best” observation during each eight day period, for every cell in the image, is retained.  This helps reduce or eliminate clouds from a scene.  The file contains the same seven spectral bands of data as the daily file listed above.  It also has an additional 6 bands of information concerning quality control, solar zenith, view zenith, relative azimuth, surface reflectance 500 m state flags, and surface reflectance day of year.

Vegetation Index Products

There are several composite MODIS vegetation products.  Sixteen-day composites are available at 250 m, 500 m, 1 km, and 0.05 degree resolutions.  There are also monthly composites with 1 km, and 0.05 degree resolutions.  Each file contains bands of data for both the traditional Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI).  There are also data quality bands in each file.

The data type is 16 bit signed integer, which has a theoretical range of values from -32,768 to +32,768.  The documented data range is from -2000 to +10000 with a fill value of -3000.  If you wish to convert these numbers to the traditional data range, cell values should be divided by 10,000.  These data must then be stored with a float data type of IEEE 4 byte real.

The Vegetation Index products have a label prefix of MOD13 for the Terra sensor and MYD13 for the Aqua sensor.  On the ordering web page the product name indicates the sensor, composite period, spatial resolution, and data version number.  For example, “MODIS/TERRA Vegetation Indices 16-day L3 Global 250m Sin Grid V005” will get you the data from Terra for a 16-day composite at 250 m resolution in the sinusoidal projection using the version 5 data

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