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Fleischer, P.

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1. Report No. it " 2!'WerAiOte t'ccession No. 3. Recipient's Catalog No.
4. Title and Subtitle INVESTIGATION TO RELATE CHLORO- 5. Report Dote
PHYLL & SUSPENDED SEDIMENT CONTENT IN WATERS
OF LOWER CHESAPEAKE BAY TO ERTS-1 IMAGERY(TAI. Performing OrganizationCode
7. Author(s 8. Performing Organization Report No.Peter Fleischer
tming Oraanizaoion. Name andc Addcss 10. Work Unit No.
fSnr i~Onion u ni vve rsity Kesearch Foundation
P. O. Box 6173 11. Contract or Grant No.
Norfolk, Va. 23508 NAS5-21816
13. Type of Report and Period Covered
12. Sponsoring Agency Name and Address Semi-Annual Report
National Aeronautics and Space Administration Aug. 4, 1972-Jan. 31,
Goddard Space Flight Center 1973
~~~~~~~~~Greenbel t Road 14. Sponsoring Agency CodeGreenbelt Road
ir_ ...e+it .Mar.yland 207711r .up~p elmen~ary Notes
16. Abstract
Objective of the project is to correlate multispectral imagery
from the Earth Resources Technology Satellite to estuarine water
character. Chesapeake Bay is used as a study area, and chlorophyll,
suspended particulates, and turbidity is being monitored during
satellite overpasses. Correlation of ground truth to satellite
data will determine the usefulness of multispectral imagery in
surveying estuarine water character and circulation without the
aid of ground truth, and will result in criteria that will
maximize the usefulness of satellite imagery for this purpose.
17. Key Words (Selected by Author(s)) 18. Distribution Statement
19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price
*For sale by the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151.
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INTRODUCTION
The objective of this project is to correlate multispectral imagery
from the Earth Resources Technology Satellite to estuarine water character.
We are using lower Chesapeake Bay as a study area, and are monitoring pri-
marily chlorophyll, suspended particulates, and turbidity during satellite
overpasses. Correlation of ground truth to satellite data will determine
the usefulness of multispectral imagery in surveying estuarine water
character and circulation without the aid of ground truth, and will result
in criteria that will maximize the usefulness of satellite imagery for
this purpose.
REPORT
Ground truth--chlorophyll and sediment analysis
Ground truth data has been collected for the October 10, December 3,
and January 26 satellite overpasses.
To date this program continues to suffer due to the lack of satellite
data. There have been three dates (Oct. 10, Dec. 3, 1972; and Jan. 26, 1973)
when the weather permitted satellite coverage of this area. We have
received data for the Oct. 10 and Jan. 26 passes, and only partial coverage
for the Dec. 3 pass.
Ground truth data has been collected for each of the above dates.
Much more structure in the water than was anticipated is visible in the
images. Because of this, it may become necessary to modify our ground
truth procedures to obtain continuous records of chlorophyll as well as
sediments. This can only be decided after more ERTS data have been received.
Regardless of whether or not this will become necessary, plans are being
made to obtain this type of information beginning this spring with the
I
2assistance of a tunable dye laser under development, to determine induced
fluorescence, by Drs. P.B. Mumola (of NASA Langley) and H.H. Kim (of NASA
Wallops Station).
Sediment analysis shows the quantity to be down nearly an order of
magnitude on Dec. 3 as compared to Oct. 10, and the size range maximum
shifted from 0.5-2 micron size range on Oct. 10 to the 2-4 micron size
range on Dec. 3. The Oct. 10 water was influenced by recent flooding
and the tide was approaching high tide, whereas the Dec. 3 data had high
water and ebbing at the time of the satellite pass. In addition to
these changes, there was a reversal of the sediment loads along the Chesa-
peake Bay Bridge Tunnel in that on Oct. 10 the larger load was on the south
end, and on Dec. 3 the larger sediment load was in the central and northern
areas. There seems to be a correlation between the sediment load count and
the ERTS images.
Ground truth--turbidity
Development and testing of the continuously recording transmissometer
system was completed in November, 1972, and monitoring of lower Chesapeake
Bay surface waters commenced in December, 1972. Sea conditions permitting,
turbidity has since been monitored during satellite overpasses on Dec. 3
and on January 26. So far, three baselines (Little Creek - Hampton,
Hampton - Cape Charles, and Cape Charles - Little Creek) have been occupied
at each of these times. Three baselines cross the three major boundaries
of lower Chesapeake Bay: the bay entrance, Hampton Roads, and the lower
central Bay.
The application of a transmissometer in this manner is essentially
a new development, and is a practical means of delineating turbidity
levels in estuarine water bodies. We have been able to determine these
3for lower Chesapeake Bay, and have found them-to be highly variable. Values
range from 0 to 60% transmittance per 0.43 m, and are dependent upon 1)
tidal stage, 2) water source, and 3) biologic activity. In addition, we
have found short-term turbidity variations, often of high magnitude, oc-
curring in some portions of the Bay, particularly in the central Bay and
the northern Bay entrance. Correlation of turbidity with the baselines
has been attempted as a preliminary step by microdensitometer, and was
found not to be too promising because of the low contrast of ,the images.
Correlation of the baselines to the bulk tapes is in an early stage, but
appears to be considerably more successful. However, proper interrogation
to extract the baselines from the tapes must still be made.
Bathymetry has also been determined along the above mentioned base-
lines, and shows some correlation to turbidity insofar as it affects flow
of water masses within the Bay.
Image analysis--Data reduction
To date, imagery has been received for three passes over the experi-
ment area; October 10, December 3 and January 26. The positive trans-
parencies have been reduced, using the microdensitometer, and the radiance
values for the green and red bands have been obtained for the 18 stations
visited by helicopter and the three baselines in the Bay entrance. The
data for the 18 stations has been tabulated to facilitate comparisons with
the satellite imagery but no correlations have been attempted. At least
three sets of data will be assembled before a rough correlation is attempted
because the two sets to date are incomplete; the ground data for the base-
lines was not collected on October 10 and the Green band is missing for
the December 3 pass (reason unknown). A rough comparison of the data seems
to show some trend between the radiance values and the chlorophyll and
particulate concentrations.
4The photographic analysis is. on'ly usied for quick look information and
to assist in the final analysis with the Computer Compatible Tapes. At
this time the reduction of the data on the tapes is continuing. A mask
has been prepared to separate the land areas from the water. This mask
will be printed to overlay CGS Chart No. 1222. In thtis way the resolution
elements representing the ground test sites can be easily found.
NEW TECHNOLOGY
The use of a ship-mounted transmissometer to monitor turbidity of
surface waters on a continuous basis is a new development. We are using
a modified Bendix C-2 Transmissometer Probe with a shortened pathlength
of 43 cm, to allow this instrument to be used in turbid estuarine waters.
A continuously recording output in the form of a Mosely Model 80A-2 recorder
was substituted for the standard manual readout, and adapted to the probe.
A battery power-supply was also installed to increase signal-to-noise
ratio (E.L. Bryant, 1973, Automatic recorder for a turbidity measurement
probe, Langley Working Paper LWP-1097, 14 p.). Sensitivity of the modified
instrument is well under 1% transmittance.
In order to use this instrument from a moving vessel, it was determined
that the most feasible way is to mount the probe on the keel. This is
accomplished by two Scuba divers in approximately 30 minutes before each
cruise. We are using the Old Dominion University Institute of Oceanography
research vessel LINWOOD HOLTON, a 65 foot T-Boat conversion, for this
purpose. Cruising speed with the probe is about 6-8 knots.
5PROGRAM FOR NEXT REPORTING INTERVAL
The program will include the following:
1. Continued monitoring of lower Chesapeake Bay during ERTS overpasses.
Baselines will be extended into the lower portion of the central Bay, and
water sampling will reflect the water structure found so far.
2. Use of a tunable dye laser to measure chlorophyll, and possible
development by NASA-Langley of a high-speed, helicopter-towed transmisso-
meter.
3. Processing of bulk tapes to correlate radiance to measured parameters,
optimization of image data, and construction of contour maps of estuarine
water parameters from the imagery.
CONCLUSION
The project is progressing as planned, but receipt of images has been
less than anticipated. Ground-truth collection is proceeding satisfactorily,
and is being modified by the results of available imagery and ground data.
Image processing is somewhat hampered by a lack of material. Completion
of results and interpretation of results will require that additional
ground truth and imagery be obtained during the second half of this project.


Investigation to relate chlorophyll and suspended sediment content in waters of lower Chesapeake Bay to ERTS-1 imagery

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