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At least 163 records · Page 9

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NASA NTRS1973

A technique for interpretation of multispectral remote sensor data

The author has identified the following significant results. The U.S. Army Engineer Waterways Experiment Station is engaged in a study to detect from ERTS-1 satellite data alterations to the absorption and scattering properties caused by movement of suspended particles and solutes in selected areas of the Chesapeake Bay and to correlate the data to determine the feasibility of delineating flow patterns, flushing action of the estuary, and sediment and pollutant dispersion. As a part of this study, ADP techniques have been developed that permit automatic interpretation of data from any multispectral remote sensor with computer systems which have limited memory capacity and computing speed. The multispectral remote sensor is considered as a reflectance spectrophotometer. The data which define the spectral reflectance characteristics of a scene are scanned pixel by pixel. Each pixel whose spectral reflectance matches a reference spectrum is identified, and the results are shown in a map that identifies the locations where spectrum matches were detected and spectrum that was matched. The interpretation technique is described and an example of interpreted data from ERTS-1 is presented.

Williamson, A. N.↗

NASA NTRS1973

New algae mapping technique by the use of an airborne laser fluorosensor.

An airborne laser fluorosensor for the detection of algae in the sea has been developed. The system transmits dye laser radiation at 590 nm and monitors the fluorescent emission at 685 nm from chlorophyll-a bearing microorganisms. The system was successfully flown over the test areas of Lake Ontario and Chesapeake Bay. The device is sensitive to a fraction of mg/cu-M chlorophyll-a density in the water from an altitude of 30 m.

Kim, H. H.↗

NASA NTRS1974

A feasibility study for a remote laser water turbidity meter

A technique to remotely determine the attenuation coefficient (alpha) of the water was investigated. The backscatter energy (theta = 180 deg) of a pulse laser (lambda = 440 - 660 nm) was found directly related to the water turbidity. The greatest sensitivity was found to exist at 440 nm. For waters whose turbidity was adjusted using Chesapeake Bay sediment, the sensitivity in determining alpha at 440 nm was found to be approximately 5 - 10%. A correlation was also found to exist between the water depth (time) at which the peak backscatter occurs and alpha.

Hickman, G. D.↗

NASA NTRS1974

Use of remote sensing in agriculture

Remote sensing studies in Virginia and Chesapeake Bay areas to investigate soil and plant conditions via remote sensing technology are reported ant the results given. Remote sensing techniques and interactions are also discussed. Specific studies on the effects of soil moisture and organic matter on energy reflection of extensively occurring Sassafras soils are discussed. Greenhouse and field studies investigating the effects of chlorophyll content of Irish potatoes on infrared reflection are presented. Selected ground truth and environmental monitoring data are shown in summary form. Practical demonstrations of remote sensing technology in agriculture are depicted and future use areas are delineated.

Pettry, D. E.↗

NASA NTRS1973

Four wavelength lidar applied to determination of chlorophyll a concentration and algae color group

A technique for remote measurement of chlorophyll a density and determination of algae color group is described. In vivo fluorescence measurements of chlorophyll a for four color groups of algae (green, golden-brown, red, and blue-green) are described, and representative spectra are shown. The lidar equation is developed for the general case of a mixture of color groups showing the need for multicolor excitation. The lidar instrument which has been designed and fabricated at Langley Research Center for helicopter flights over surrounding portions of the Chesapeake Bay is described. The lidar package contains a unique four-color dye laser which permits multicolor excitation of chlorophyll a fluorescence from the various color groups of algae.

Jarrett, O., Jr.↗

NASA NTRS1974

Land use and mapping

The ERTS program provides data that can be used to derive information relative to the actual use of the land resource, in a practical and timely manner. ERTS data provide coverage of total land areas, and its repetitive nature enables the detection and monitoring of changes taking place in land use. Generally, the techniques and the procedures used to extract information from ERTS data may be categorized as pertaining to either the interpretations of ERTS imagery or to the use of digital data and computer techniques. Examples are given of the use of ERTS-1 data for land use classification in: (1) New England areas; (2) Chesapeake Bay and Washington, D.C.; (3) Mississippi Gulf Coast; (4) Los Angeles, California; (5) Houston, Texas; and (6) Phoenix, Arizona.

Joyce, A. T.↗

NASA NTRS1975

Auxiliary DCP data acquisition system

An airborne DCP Data Aquisition System has been designed to augment the ERTS satellite data recovery system. The DCP's are data collection platforms located at pertinent sites. With the appropriate sensors they are able to collect, digitally encode and transmit environmental parameters to the ERTS satellite. The satellite in turn relays these transmissions to a ground station for processing. The satellite is available for such relay duty a minimum of two times in a 24-hour period. The equipment is to obtain continuous DCP data during periods of unusual environmental activity--storms, floods, etc. Two circumstances contributed to the decision to design such a system; (1) Wallops Station utilizes surveillance aircraft in support of rocket launches and also in support of earth resources activities; (2) the area in which Wallops is located, the Delaware and Chesapeake Bay areas, are fertile areas for DCP usage. Therefore, by developing an airborne DCP receiving station and installing it on aircraft more continuous DCP data can be provided from sites in the surrounding areas at relatively low cost.

Snyder, R. V.↗

NASA NTRS1975

Classification of wetlands vegetation using small scale color infrared imagery

A classification system for Chesapeake Bay wetlands was derived from the correlation of film density classes and actual vegetation classes. The data processing programs used were developed by the Laboratory for the Applications of Remote Sensing. These programs were tested for their value in classifying natural vegetation, using digitized data from small scale aerial photography. Existing imagery and the vegetation map of Farm Creek Marsh were used to determine the optimal number of classes, and to aid in determining if the computer maps were a believable product.

Williamson, F. S. L.↗

NASA NTRS1975

Development of an airborne laser bathymeter

An airborne laser depth sounding system was built and taken through a complete series of field tests. Two green laser sources were tried: a pulsed neon laser at 540 nm and a frequency-doubled Nd:YAG transmitter at 532 nm. To obtain a depth resolution of better than 20 cm, the pulses had a duration of 5 to 7 nanoseconds and could be fired up to at rates of 50 pulses per second. In the receiver, the signal was detected by a photomultiplier tube connected to a 28 cm diameter Cassegrainian telescope that was aimed vertically downward. Oscilloscopic traces of the signal reflected from the sea surface and the ocean floor could either be recorded by a movie camera on 35 mm film or digitized into 500 discrete channels of information and stored on magnetic tape, from which depth information could be extracted. An aerial color movie camera recorded the geographic footprint while a boat crew of oceanographers measured depth and other relevant water parameters. About two hundred hours of flight time on the NASA C-54 airplane in the area of Chincoteague, Virginia, the Chesapeake Bay, and in Key West, Florida, have yielded information on the actual operating conditions of such a system and helped to optimize the design. One can predict the maximum depth attainable in a mission by measuring the effective attenuation coefficient in flight. This quantity is four times smaller than the usual narrow beam attenuation coefficient. Several square miles of a varied underwater landscape were also mapped.

Kim, H., H.↗

NASA NTRS1974

Coastal wetlands analysis from ERTS MSS digital data and field spectral measurements

Classification, delineation and evaluation of coastal wetlands can be made on the basis of major vegetative associations. To produce wetland maps, two vegetation-analysis look-up tables were developed for use in the ERTS ANALYSIS System. These look-up tables are based on Earth Resources Technology Satellite (ERTS) digital values in Multispectral Scanner (MSS) bands 4, 5, and 7 and were developed using seasonal spectral reflectance measurements from field observations. Computer-generated maps at an approximate scale of 1:20,000 were produced for the primary test site, Chincoteague Marsh, Virginia. There is a high degree of accuracy in the identification of wetland features and plant associations. The classification was also tested on other Atlantic coast salt marshes and a brackish marsh in the Chesapeake Bay.

Carter, V.↗

NASA NTRS1975

Applications of remote sensing to estuarine problems

A variety of siting problems for the estuaries of the lower Chesapeake Bay have been solved with cost beneficial remote sensing techniques. Principal techniques used were repetitive 1:30,000 color photography of dye emitting buoys to map circulation patterns, and investigation of water color boundaries via color and color infrared imagery to scales of 1:120,000. Problems solved included sewage outfall siting, shoreline preservation and enhancement, oil pollution risk assessment, and protection of shellfish beds from dredge operations.

Munday, J. C., Jr.↗

NASA NTRS1976

The use of ERTS-1 to more fully utilize and apply marine station data to the study and productivity along the eastern shelf waters of the United States

The author has identified the following significant results. Sea truth data were obtained during two ERTS overpasses in waters near the entrance of the Chesapeake Bay. Correlations were made between total phytoplankton and chlorophyll values in these waters to radiance detected by ERTS in an effort to map areas of similar productivity levels. Band 4 radiance had the highest correlation to all parameters with bands 5 and 6 showing decreasing correlations in each case. The radiance values were apparently influenced by one or more factors, most likely including the sediment content of the water. Data have shown that ERTS MSS is not suitable for monitoring chlorophyll in near-shore waters where sediment loads are high. It is suggested that in more seaward or pelagic locations, that ERTS MSS would be more efficient in monitoring surface chlorophyll values and establishing direct relationships to phytoplankton concentrations.

Marshall, H. G.↗

NASA NTRS1976

Processing of LANDSAT imagery for dissemination purposes

The author has identified the following significant results. The differentiation between bands 4 and 5 was achieved through enhancement. Depiction of dormant vegetation on the upper Chesapeake Bay image map in tones of green is an example of significant difference between bands 4 and 5 which can be achieved through proper enhancement.

Colvocoresses, A. P.↗

NASA NTRS1976

Overall evaluation of LANDSAT (ERTS) follow-on imagery for cartographic application

The author has identified the following significant results. The NASA/Cousteau experiment showed that under suitable conditions and with calibration data, the bottom of clear tropical seas can be mapped with LANDSAT to a depth of 22 meters with a root-mean-square error of about 10 percent. This application required the high gain setting of band 4 of the MSS. The experiment also confirmed that a somewhat lower waveband than band 4 would increase the water penetration capability of future LANDSATS. Other experiments illustrated by the reprinting of upper Chesapeake Bay indicate that the original LANDSAT signals must be modulated and optimized for the photographic and lithographic processes. Work by the Canadian mapping agency indicates significant improvements in the control identification and geometric accuracy of LANDSAT cartographic applications.

Colvocoresses, A. P.↗

NASA NTRS1976

Applications of remote sensing to estuarine management

Projects for sewage outfall siting for pollution control in the lower Chesapeake Bay wetlands are reported. A dye-buoy/photogrammetry and remote sensing technique was employed to gather circulation data used in outfall siting. This technique is greatly favored over alternate methods because it is inexpensive, produces results quickly, and reveals Lagrangian current paths which are preferred in making siting decisions. Wetlands data were obtained by interpretation of color and color infrared photographic imagery from several altitudes. Historical sequences of photographs are shown that were used to document wetlands changes. Sequential infrared photography of inlet basins was employed to determine tidal prisms, which were input to mathematical models to be used by state agencies in pollution control. A direct and crucial link between remote sensing and management decisions was demonstrated in the various projects.

Munday, J. C., Jr.↗

NASA NTRS1975

Quantitative sediment mapping from remotely sensed multispectral data

Multiple regression techniques were used to correlate ERTS-1 data with measured values of suspended sediment. The resultant equation was applied to a different ERTS scene using a deepwater area for atmospheric calibration. This approach provides greater accuracy than previously reported methods. Suspended sediment contours are plotted for the Potomac River, Virginia, using Chesapeake Bay deep water for atmospheric calibration.

Johnson, R. W.↗

NASA NTRS1975

Drogue performance evaluation. Part 1: Data acquisition

Surface buoy/subsurface drogue drag coupling was investigated. Data acquisition methods and techniques derived from several experimental cruises on the Chesapeake Bay are presented. Four buoys were utilized: three coupled to steel plates rigidly attached to each other at right angles and at various depths; and one spar type that did not require drag plates. Data from these surface floats and the drogue depth combinations were processed. Errors in tracking the surface buoys are discussed.

Johnson, R. E.↗

NASA NTRS1978

Remote sensing, geology, and land use

The usefulness of a geologic map as a product in geological research was discussed, and the volution of the geologic map of Maryland was illustrated. Remote sensing methods that have the most immediate application to the earth science aspects of the Chesapeake Bay region are listed.

Weaver, K. N.↗