Abstract

Directional reflectance factors of an alfalfa canopy were determined and related to canopy structure, agronomic variables, and irradiance conditions at four periods during a cutting cycle. Nadir and off-nadir reflectance factors decreased with increasing biomass in Thematic Mapper band 3 (0.63–0.69 μm) and increased with increasing biomass in band 4 (0.76–0.90 μm). The sensor view angle had less impact on perceived reflectance as the alfalfa progressed from an erectophile canopy of stems after harvest to a near planophile canopy of leaves at maturity. Studies of directional reflectance are needed for testing and upgrading vegetation canopy models and to aid in the complex interpretation problems presented by aircraft scanners and pointable satellites where illumination and viewing geometries may vary widely. Distinct changes in the patterns of radiance observed by a sensor as structural and biomass changes occur are keys to monitoring the growth and condition of crops.

© 1982 Optical Society of America

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References

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  1. J. A. Smith, K. J. Ranson, MRS Literature Survey of Bidirectional Reflectance, ORI, Inc. Contract Report to NASA/GSFC (Oct.1979).
  2. D. S. Kimes, J. A. Smith, K. J. Ranson, Photogramm. Eng. Remote Sensing 46, 1563 (1980).
  3. J. A. Kirchner, C. C. Schnetzler, J. A. Smith, Int. J. Remote Sensing, 2, 253 (1981).
    [CrossRef]
  4. J. A. Smith, R. E. Oliver, Appl. Opt. 13, 1599 (1974).
    [CrossRef] [PubMed]
  5. J. A. Smith, J. K. Berry, F. Heimes, Signature Extension for Sun Angle, EOD, NASA, JSC, NAS9-14467, Final Report (1975).
  6. D. S. Kimes, J. A. Kirchner, Remote Sensing Environ. 12, 141 (1981).
    [CrossRef]
  7. C. J. Tucker, W. H. Jones, W. A. Kley, G. J. Sundstrom, Science 211, 281 (1981).
    [CrossRef] [PubMed]
  8. W. Mendenhall, L. Ott, R. L. Scheaffer, Elementary Survey Sampling (Wadsworth, Belmont, Calif., 1971), 247 pp.
  9. C. T. de Wit, Photosynthesis on Leaf Canopies (Institute for Biological and Chemical Research on Field Crops and Herbage, Centre for Agricultural Publications and Documentation, Wageningen, The Netherlands, 1965), 57 pp.
  10. V. V. Salomonson, W. E. Marlatt, Remote Sensing Environ. 2, 1 (1971).
    [CrossRef]
  11. D. D. Egbert, F. T. Ulaby, Photogramm. Eng. 38, 556 (1972).
  12. K. J. Ranson, V. C. Vanderbilt, L. L. Biehl, B. F. Robinson, M. E. Bauer, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).
  13. K. Staenz, F. J. Ahern, R. J. Brown, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).
  14. K. T. Kriebel, Remote Sensing Environ. 4, 257 (1976).
    [CrossRef]
  15. C. C. Schnetzler, “On the Use of Off-Nadir Pointing for Increased Temporal Resolution of Earth Observing Satellite Systems,” NASA Tech. Memo. 82139 (1981), 27 pp.

1981 (3)

J. A. Kirchner, C. C. Schnetzler, J. A. Smith, Int. J. Remote Sensing, 2, 253 (1981).
[CrossRef]

D. S. Kimes, J. A. Kirchner, Remote Sensing Environ. 12, 141 (1981).
[CrossRef]

C. J. Tucker, W. H. Jones, W. A. Kley, G. J. Sundstrom, Science 211, 281 (1981).
[CrossRef] [PubMed]

1980 (1)

D. S. Kimes, J. A. Smith, K. J. Ranson, Photogramm. Eng. Remote Sensing 46, 1563 (1980).

1976 (1)

K. T. Kriebel, Remote Sensing Environ. 4, 257 (1976).
[CrossRef]

1974 (1)

1972 (1)

D. D. Egbert, F. T. Ulaby, Photogramm. Eng. 38, 556 (1972).

1971 (1)

V. V. Salomonson, W. E. Marlatt, Remote Sensing Environ. 2, 1 (1971).
[CrossRef]

Ahern, F. J.

K. Staenz, F. J. Ahern, R. J. Brown, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).

Bauer, M. E.

K. J. Ranson, V. C. Vanderbilt, L. L. Biehl, B. F. Robinson, M. E. Bauer, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).

Berry, J. K.

J. A. Smith, J. K. Berry, F. Heimes, Signature Extension for Sun Angle, EOD, NASA, JSC, NAS9-14467, Final Report (1975).

Biehl, L. L.

K. J. Ranson, V. C. Vanderbilt, L. L. Biehl, B. F. Robinson, M. E. Bauer, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).

Brown, R. J.

K. Staenz, F. J. Ahern, R. J. Brown, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).

de Wit, C. T.

C. T. de Wit, Photosynthesis on Leaf Canopies (Institute for Biological and Chemical Research on Field Crops and Herbage, Centre for Agricultural Publications and Documentation, Wageningen, The Netherlands, 1965), 57 pp.

Egbert, D. D.

D. D. Egbert, F. T. Ulaby, Photogramm. Eng. 38, 556 (1972).

Heimes, F.

J. A. Smith, J. K. Berry, F. Heimes, Signature Extension for Sun Angle, EOD, NASA, JSC, NAS9-14467, Final Report (1975).

Jones, W. H.

C. J. Tucker, W. H. Jones, W. A. Kley, G. J. Sundstrom, Science 211, 281 (1981).
[CrossRef] [PubMed]

Kimes, D. S.

D. S. Kimes, J. A. Kirchner, Remote Sensing Environ. 12, 141 (1981).
[CrossRef]

D. S. Kimes, J. A. Smith, K. J. Ranson, Photogramm. Eng. Remote Sensing 46, 1563 (1980).

Kirchner, J. A.

J. A. Kirchner, C. C. Schnetzler, J. A. Smith, Int. J. Remote Sensing, 2, 253 (1981).
[CrossRef]

D. S. Kimes, J. A. Kirchner, Remote Sensing Environ. 12, 141 (1981).
[CrossRef]

Kley, W. A.

C. J. Tucker, W. H. Jones, W. A. Kley, G. J. Sundstrom, Science 211, 281 (1981).
[CrossRef] [PubMed]

Kriebel, K. T.

K. T. Kriebel, Remote Sensing Environ. 4, 257 (1976).
[CrossRef]

Marlatt, W. E.

V. V. Salomonson, W. E. Marlatt, Remote Sensing Environ. 2, 1 (1971).
[CrossRef]

Mendenhall, W.

W. Mendenhall, L. Ott, R. L. Scheaffer, Elementary Survey Sampling (Wadsworth, Belmont, Calif., 1971), 247 pp.

Oliver, R. E.

Ott, L.

W. Mendenhall, L. Ott, R. L. Scheaffer, Elementary Survey Sampling (Wadsworth, Belmont, Calif., 1971), 247 pp.

Ranson, K. J.

D. S. Kimes, J. A. Smith, K. J. Ranson, Photogramm. Eng. Remote Sensing 46, 1563 (1980).

K. J. Ranson, V. C. Vanderbilt, L. L. Biehl, B. F. Robinson, M. E. Bauer, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).

J. A. Smith, K. J. Ranson, MRS Literature Survey of Bidirectional Reflectance, ORI, Inc. Contract Report to NASA/GSFC (Oct.1979).

Robinson, B. F.

K. J. Ranson, V. C. Vanderbilt, L. L. Biehl, B. F. Robinson, M. E. Bauer, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).

Salomonson, V. V.

V. V. Salomonson, W. E. Marlatt, Remote Sensing Environ. 2, 1 (1971).
[CrossRef]

Scheaffer, R. L.

W. Mendenhall, L. Ott, R. L. Scheaffer, Elementary Survey Sampling (Wadsworth, Belmont, Calif., 1971), 247 pp.

Schnetzler, C. C.

J. A. Kirchner, C. C. Schnetzler, J. A. Smith, Int. J. Remote Sensing, 2, 253 (1981).
[CrossRef]

C. C. Schnetzler, “On the Use of Off-Nadir Pointing for Increased Temporal Resolution of Earth Observing Satellite Systems,” NASA Tech. Memo. 82139 (1981), 27 pp.

Smith, J. A.

J. A. Kirchner, C. C. Schnetzler, J. A. Smith, Int. J. Remote Sensing, 2, 253 (1981).
[CrossRef]

D. S. Kimes, J. A. Smith, K. J. Ranson, Photogramm. Eng. Remote Sensing 46, 1563 (1980).

J. A. Smith, R. E. Oliver, Appl. Opt. 13, 1599 (1974).
[CrossRef] [PubMed]

J. A. Smith, K. J. Ranson, MRS Literature Survey of Bidirectional Reflectance, ORI, Inc. Contract Report to NASA/GSFC (Oct.1979).

J. A. Smith, J. K. Berry, F. Heimes, Signature Extension for Sun Angle, EOD, NASA, JSC, NAS9-14467, Final Report (1975).

Staenz, K.

K. Staenz, F. J. Ahern, R. J. Brown, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).

Sundstrom, G. J.

C. J. Tucker, W. H. Jones, W. A. Kley, G. J. Sundstrom, Science 211, 281 (1981).
[CrossRef] [PubMed]

Tucker, C. J.

C. J. Tucker, W. H. Jones, W. A. Kley, G. J. Sundstrom, Science 211, 281 (1981).
[CrossRef] [PubMed]

Ulaby, F. T.

D. D. Egbert, F. T. Ulaby, Photogramm. Eng. 38, 556 (1972).

Vanderbilt, V. C.

K. J. Ranson, V. C. Vanderbilt, L. L. Biehl, B. F. Robinson, M. E. Bauer, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).

Appl. Opt. (1)

Int. J. Remote Sensing (1)

J. A. Kirchner, C. C. Schnetzler, J. A. Smith, Int. J. Remote Sensing, 2, 253 (1981).
[CrossRef]

Photogramm. Eng. (1)

D. D. Egbert, F. T. Ulaby, Photogramm. Eng. 38, 556 (1972).

Photogramm. Eng. Remote Sensing (1)

D. S. Kimes, J. A. Smith, K. J. Ranson, Photogramm. Eng. Remote Sensing 46, 1563 (1980).

Remote Sensing Environ. (3)

D. S. Kimes, J. A. Kirchner, Remote Sensing Environ. 12, 141 (1981).
[CrossRef]

V. V. Salomonson, W. E. Marlatt, Remote Sensing Environ. 2, 1 (1971).
[CrossRef]

K. T. Kriebel, Remote Sensing Environ. 4, 257 (1976).
[CrossRef]

Science (1)

C. J. Tucker, W. H. Jones, W. A. Kley, G. J. Sundstrom, Science 211, 281 (1981).
[CrossRef] [PubMed]

Other (7)

W. Mendenhall, L. Ott, R. L. Scheaffer, Elementary Survey Sampling (Wadsworth, Belmont, Calif., 1971), 247 pp.

C. T. de Wit, Photosynthesis on Leaf Canopies (Institute for Biological and Chemical Research on Field Crops and Herbage, Centre for Agricultural Publications and Documentation, Wageningen, The Netherlands, 1965), 57 pp.

J. A. Smith, K. J. Ranson, MRS Literature Survey of Bidirectional Reflectance, ORI, Inc. Contract Report to NASA/GSFC (Oct.1979).

J. A. Smith, J. K. Berry, F. Heimes, Signature Extension for Sun Angle, EOD, NASA, JSC, NAS9-14467, Final Report (1975).

C. C. Schnetzler, “On the Use of Off-Nadir Pointing for Increased Temporal Resolution of Earth Observing Satellite Systems,” NASA Tech. Memo. 82139 (1981), 27 pp.

K. J. Ranson, V. C. Vanderbilt, L. L. Biehl, B. F. Robinson, M. E. Bauer, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).

K. Staenz, F. J. Ahern, R. J. Brown, in Proceedings, Fifteenth International Symposium on Remote Sensing of Environment (Environmental Research Institute of Michigan, Ann Arbor, 1981).

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Figures (8)

Fig. 1
Fig. 1

Geometry of incident and reflected rays. By definition the solar vector lies within the x-z plane with azimuth γ′ always equal to 180°. The solar zenith angle is θ, and the relative sensor azimuth is γ. The off-nadir view angle of the sensor is α. A sensor with a relative azimuth of 0 looks toward the sun. The shaded plane represents the sun’s principal plane which contains the x and z axes.

Fig. 2
Fig. 2

Discrete and cumulative inclination angle distributions for (a) stems (9 July) and (b) leaves (15 and 31 July). Bounds on the error of estimation (two times the standard error) are shown on the discrete values. Theoretical conical and planophile distributions are presented for comparison.

Fig. 3
Fig. 3

Corrected and uncorrected reflectance factors in the nadir direction for the TM4 band for 15 and 31 July as a function of solar zenith angle.

Fig. 4
Fig. 4

Corrected nadir reflectance factors for TM bands 3 (a) and 4 (b) as a function of solar zenith angle. Bounds on the error of estimation (two times the standard error) are shown.

Fig. 5
Fig. 5

Directional reflectance factors of an alfalfa canopy in TM3 band (0.63–0.69 μm) at four periods during a cutting cycle. Equal lines of reflectance are contoured in a polar coordinate system where the distance from the origin represents the off-nadir view angle of the sensor, and the angle from 0 represents the sensor’s azimuth relative to the solar azimuth. As defined in the text and Fig. 1, the solar azimuth is always 180°, and a sensor with a relative azimuth of 0 looks into the sun. Only half of the total exitance hemisphere is shown because azimuthal symmetry of the alfalfa’s structure about the principal plane of the sun was assumed.

Fig. 6
Fig. 6

Directional reflectance factors of an alfalfa canopy in TM4 band (0.76–0.90 μm) at four periods during a cutting cycle. The coordinate system is explained in Fig. 5.

Fig. 7
Fig. 7

Directional reflectance factors of an alfalfa canopy in TM bands 3 and 4 for three solar zenith angles (21, 42, and 54°) on 9 July 1980. On this date the canopy had an extreme erectophile, or conical, structure with 42% cover. The coordinate system is explained in Fig. 5.

Fig. 8
Fig. 8

Directional reflectance factors of an alfalfa canopy in TM bands 3 and 4 for three solar zenith angles (21, 47, and 57°) on 31 July 1980. On this date the canopy had a nearly planophile structure with 92% cover. The coordinate system is explained in Fig. 5.

Tables (5)

Tables Icon

Table I Date, Mean Solar Zenith Angle, and Mean of the Corrected, Spectral, Direct/Global Ratios of the 24 Measurement Periods

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Table II Agronomic Characteristics of Alfalfa. Bounds on the Error of Estimation (Two Times the Standard Error) are Followed by the Sample Size in Parentheses

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Table III Nadir Reflectance Factors a of an Alfalfa Canopy and Maximum Percent Deviation of Off-Nadir Reflectance Factors from the Nadir in TM3 and TM4 bands on Four Dates During a Cutting Cycle

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Table IV Nadir Reflectance Factors of an Alfalfa Canopy in Band TM3 and Maximum Percent Deviation of Off-Nadir Reflectance Factors from the Nadir Value as a Function of Solar Zenith Angle on Two Dates

Tables Icon

Table V Nadir Reflectance Factors a of an Alfalfa Canopy in Band TM4 and Maximum Percent Deviation of Off-Nadir Reflectance Factors from the Nadir Value as a Function of Solar Zenith Angle on Two Dates

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