Processing and Georeferencing Raw Satellite Imagery Using ENVI
Anonym
Customer Challenge
Both Commercial and recreational fisherman are always looking for better ways to find concentrations of fish and increase their catch. Roffer’s Ocean Fishing Forecasting Service, Inc (ROFFSä) in Miami, Florida thought there might be a way, using satellite data, to solve the problem.
Solution Achieved
Roffers uses sea surface temperature (SST) and Ocean-Color/Chlorophyll satellite imagery from the National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA) to locate the most favorable conditions for fishing success. Their oceanographers analyze satellite imagery using ENVI®, and, combined with additional information from various sources, they are able to produce detailed, real-time assessments of fishing conditions.
Roffers uses ENVI because it provides advanced functionality for calibrating, warping, and georeferencing many types of satellite imagery, including multispectral and hyperspectral. ENVI's suite of spectral processing tools allow them to transform raw satellite data into intuitive images that detail areas of seal life concentrations.
Using ENVI in conjunction with IDL®, they transform raw satellite data, mainly Advanced Very High Resolution Radiometer (AVHRR) data from NOAA and Moderate Resolution Imaging Spectroradiometer (MODIS) data from NASA, into formatted images catered toward our analysis procedure. ENVI contains tools that assist in preprocessing by calibrating the SST using the appropriate algorithm that is needed for each individual satellite. Once calibrated, ENVI provides a choice of functions to transform and re-project the image to the needed specifications.
For example, an area of interest (AOI) is defined by latitude and longitude coordinates, as well as image width and height. Once defined, the ENVI user can choose from a number of different projection types, or define his own projection depending on the part of the world in question, and apply those to the process. ENVI provides a range of mathematical interpolation methods to warp the calibrated satellite imagery based on the users specifically georeferenced AOI.
Once the imagery is geo-navigated to a specific projection and AOI, ENVI makes it possible to change the output parameters of the image, such as the data pixel size and values, to match the needed color palette. This is done by using the band math and different stretch procedures included with ENVI. Finally, ENVI provides a wide range of "save as" formats for the images, which allows Roffs to produce a final output image suitable for nearly any platform. In addition, ENVI allows Roffs to customize images with a number of parameter choices for each file type, including resolution, graphics colors, and more.
Although the image analysts at Roffs must have significant knowledge of satellite imagery and programming to complete these procedures, ENVI makes the process much less difficult and less time consuming. ENVI's automated and semi-automated functionality has allowed the team to simplify their satellite image processing, and they frequently call on the ENVI technical support team to assist in getting the results they need.
"We have only begun to utilize the capabilities of ENVI’s many functions," said Upton. "Thanks to ENVI and their technical support staff, our company is able to benefit by producing our own imagery from raw satellite data without having to purchase the processed imagery from outside organizations. This allows us to conduct scientific research and expand our analyses domain for clients around the world."
Key Benefits
- According to the customer, "As we learn more about ENVI’s capabilities we are confident that we will be able to increase the quality of our final imagery results and provide improved analyses while expanding our service, which will allow our company to grow and be more profitable."
- Thanks to ENVI and their technical support staff, our company is able to benefit by producing our own imagery from raw satellite data without having to purchase the processed imagery from outside organizations. This allows us to conduct scientific research and expand our analyses domain for clients around the world.
- ENVI's built in functionality and routines saved the team time and money.