Imagery Sources

LANDSAT

This Landsat TM image shows Lake Sakakawea, ND taken in June, 2006. The color combination used assigns Red, Green and Blue to bands 4, 3 and 2 in a false-color-composite infrared presentation.

Extensive Archive

We have nearly complete coverage across the UMAC region of selected scenes from the Landsat series of spacecraft, some locations with many years of archived imagery. When choosing the sensor source on Digital NGP, you will not see a Landsat selection - instead you will see choices of the various sensors carried aboard the different Landsat spacecraft over the years - MSS, TM, ETM+, and ETM+Pan. The TM and subsequent Landsat sensors have 7 spectral bands, most having spatial resolution of 30 meters, and acquire imagery of a given location on the ground every 16 days. Spatial coverage of a Landsat scene is 185 km x 70 km. See the Sensors section of our website for more information on these sensors or the Landsat spacecraft.

EROS Data Center

Most of our Landsat holdings have been acquired from the Earth Resources Observation and Science (EROS) Data Center, operated by the U.S. Geological Survey, which is located in Sioux Falls, SD. Each year UMAC purchases additional extensive sets of Landsat imagery. The ordered Landsat data are generally delivered to the UMAC Geospatial Lab within two days. The data delivered are terrain corrected products which include radiometric and geometric correction and ortho-rectification. The UMAC Geospatial Lab further applies atmospheric corrections using the commercial image processing software ERDAS Imagine (Leica Geosystems LLC). All seven Landsat bands, natural color composite, NDVI, and green NDVI are individually downloadable through DNGP.

ASTER

Burn scar in Yellowstone National Park, WY acquired on July 2, 2001 and simulated natural color ASTER image. Red, green and blue are allocated to ASTER band 2, 1 and 3. Burned areas appear gray, in contrast to the dark green of unburned forests.

Similar to Landsat

The ASTER sensor, built by Japan, is one of a number of instrument sensor systems on-board NASA’s Terra spacecraft. Different spectral bands of ASTER imagery are acquired at different spatial resolutions; the Visible and NIR bands (bands 1-3), which are very close spectrally to the comparable spectral bands of Landsat, have 15 meter resolution. Spatial coverage of an ASTER scene is 60x60 km. ASTER scenes thus have much smaller area coverage than Landsat, but have twice the spatial resolution (which means four ASTER pixels for every Landsat pixel). See the Sensors section of our website for more information on ASTER or the Terra spacecraft.

New Addition To Archive

Via a successful ASTER Science Team Acquisition Request (STAR) proposal, during 2006 UMAC obtained more than 150 ASTER scenes over the UMAC region. UMAC acquires ASTER scenes from The Land Processes Distributed Active Archive Center (LP DAAC); unlike the 2-day latency of Landsat, ASTER scenes can only be acquired after about a week to 10 days time. We acquire imagery that has radiometric, geometric, and ortho corrections applied. The UMAC Geospatial Lab further applies atmospheric corrections using the commercial image processing software ERDAS Imagine (Leica Geosystems LLC). Three ASTER bands (green, red, and NIR), a natural color composite, NDVI, and green NDVI are individually downloadable through DNGP.

A few ASTER scenes in selected areas were acquired prior to 2006. We anticipate being able to continue to acquire ASTER scenes via the STAR program in subsequent years.

MODIS

This MODIS image shows Wisconsin and Great Lake area taken on August 15, 2006. The color combination used assigns Red, Green and Blue to bands 1, 4 and 3 in a true color representation.

Daily Coverage

There are currently two MODIS sensors operating simultaneously in orbit, one each onboard the NASA Terra and Aqua spacecraft. MODIS collects data at a much larger scale than Landsat or ASTER, and is thus ideal for monitoring large-scale changes in the biosphere. MODIS collects data in many different spectral bands at a range of spatial resolution; bands 1 and 2 in the Visible and NIR have 250 meter resolution. While this imagery is much more coarse than ASTER or Landsat, with multiple sensors and the wide MODIS swath width (2,330 km), some MODIS data is available every day for almost the entire globe. See the Sensors section of our website for more information on the MODIS sensor or the Terra or Aqua spacecraft.

Weekly Composites

UMAC acquires daily MODIS data from a direct downlink receiving station operated by the Space Science and Engineering Center (SSEC) at the University of Wisconsin. The MODIS red and NIR band reflectance data are processed in the UMAC Geospatial Lab using our in-house semi-automated procedures, which select the maximum value in each pixel during a weekly period. The resultant weekly composite data is then subset to the UMAC region and posted to the DNGP server. Two MODIS bands (red and NIR), natural color composite, NDVI, and green NDVI at 250m spatial resolution can be downloaded through DNGP.

AEROCAM

This AEROCam CIR image was taken in eastern North Dakota during the summer of 2006 and is comprised of near infrared, red and green color bands.

High Resolution Airborne Imagery

UMAC operates the AEROCam (Airborne Environmental Research Observational Camera) system to support end users who request high resolution airborne imagery for on-the-farm evaluation of remote sensing imagery applications, as well as to support collaborative research with other UMAC academic institutions. AEROCam acquires 3-band multi-spectral imagery at high resolution, typically from 2 meters down to 0.5 meters. Areas of interest are usually around 1 square mile, though up to 25 square miles (or more) have been acquired to support specialized investigations. See the AEROCam section of our website for more information on its sensor or to find out how you can participate in AEROCam operations.

Geo-rectification

AEROCam imagery is delivered immediately (within a few days) to requesting end users in raw image format, either via our FTP server or on digital media via the mail (or on occasion, right from the plane at the local airport). In addition, each year we attempt to geo-rectify as many of the AEROCam images we collect as possible, but geo-rectification is quite labor intensive and depends on resources available in our Geospatial Lab each season. If performed, delivery of a geo-rectified product takes several weeks or longer. Once they are geo-rectified, AEROCam image products are also made available for download via DNGP.

SRTM

An SRTM image (Landsat path 37, row 29.) Brighter areas represent higher elevation and darker areas represent lower elevation.

Shuttle Radar Topography Mission

The Shuttle Radar Topography Mission (SRTM) obtained elevation data on a near-global scale to generate the most complete high-resolution digital topographic database of Earth. The Shuttle Radar Topography Mission (SRTM) was a joint project between NASA and the NGA (National Geospatial-Intelligence Agency) to map the world in three dimensions. SRTM consisted of a specially modified radar system that flew onboard the Space Shuttle Endeavour during an 11-day mission in February of 2000.

USGS Seamless Data Distribution System

Most of our SRTM data has been acquired from the USGS Seamless Data Distribution System (SDDS). DNGP has archived 30 m spatial resolution SRTM data which provides almost entire coverage over the UMAC region. Spatial coverage of one SRTM dataset provided by DNGP is about 250 km x 250 km or less. SRTM data is downloadable through DNGP using the same naming convention as Landsat path and row.