A synthetic aperture radar (SAR) is an active sensor transmitting pulses of polarized electromagnetic waves and receiving the backscattered radiation. SAR sensors at different wavelengths and with different polarimetric capabilities are being used in remote sensing of the earth. The value of an analysis of backscattered energy alone is limited due to ambiguities in the possible ecological factor configurations causing the signal. From two SAR images taken from similar viewing positions with a short time-lag, interference between the two waves can be observed. By subtracting the two phases of the signals, it is feasible to eliminate the random contribution of the scatterers to the phase. The interferometric correlation and the interferometric phase contain additional information on the three-dimensional structure of the scattering elements in the imaged area. A brief review of SAR sensors is given, followed by an outline of the physical foundations of SAR interferometry and the practical data-processing steps involved. An overview of applications of InSAR to forest mapping and monitoring is given, covering tree-bole volume and biomass, forest types and land cover, fire scars, forest thermal state and forest canopy height.
Askne, J. I. H., Dammert, P. B. G., Ulander, L. M. H. and Smith, G.1997: C-band repeat-pass interferometric SAR observations of the forest. IEEE oransactions on Geoscience and Remote Sensing35, 25-35.
2.
Baker, J. R. and Luckman, A. J. (1999): Microwave observations of boreal forests in the NOPEX area of Sweden and a comparison with observations of a temperate plantation in the UK. Journal of Agricultural and Forest Meteorology98/99, 389-416.
3.
Baker, J. R., Mitchell, P. L., Cordey, R. A., Groom, G. B., Settle, J. J. and Stileman, M. R.1994: Relationships between physical characteristics and polarimetric radar backscatter for Corsican pine stands in Thetford Forest, UK. International Journal of Remote Sensing15, 2827-2849.
4.
Bamler, R. and Hartl, P.1998: Synthetic aperture radar interferometry. Inverse Problems14, R1-R54.
5.
Chang, A. T. C., Foster, J. L., Hall, D. K., Goodison, B. E., Walker, A. E., Metcalfe, J. R. and Harby, A.1997: Snow parameters derived from microwave measurements during the BOREAS winter field campaign. Journal of Geophysical Research - Atmospheres102, 29 663-671.
6.
Christensen, E. L., Skou, N., Dall, J., Woelders, K. W., Jorgensen, J. H., Granholm, J. and Madsen, S. N.1998: EMISAR: an absolutely calibrated polarimetric L- and C-band SAR. IEEE Transactions on Geoscience and Remote Sensing36, 1852-1865.
7.
Cloude, S. R. and Papathanassiou, K. P.1998: Polarimetric SAR interferometry. IEEE Transactions on Geoscience and Remote Sensing36, 1551-1565.
8.
Coltelli, M., Fornaro, G., Franceschetti, G., Lanari, R., Migliaccio, M., Moreira, J. R., Papathanassiou, K. P., Puglisi G., Riccio, D. and Schwabisch, M.1996: SIR-C/X-SAR multi-frequency multipass interferometry: a new tool for geological interpretation. Journal of Geophysical Research - Planets101, 23127-148.
9.
Costantini, M.1998: A novel phase unwrapping method based on network programming. IEEE Transactions on Geoscience and Remote Sensing36, 813-821.
10.
Costantini, M., Farina, A. and Zirilli, F.1999: A fast phase unwrapping algorithm for SAR interferometry. IEEE Transactions on Geoscience and Remote Sensing37, 452-460.
11.
Dammert, P. B. G., Askne, J. I. H. and Kuhlmann, S.1999: Unsupervised segmentation of multi-temporal interferometric SAR images. IEEE Transactions on Geoscience and Remote Sensing37, 2259-2271.
12.
Delia, S. and Biasutti, R.1999: DESCW: PC software supporting remote sensing data. Esa Bulletin - European Space Agency97, 84-88.
13.
Dobson, M. C., Ulaby, F. T., Letoan, T., Beaudoin, A., Kasischke, E. S. and Christensen, N.1992: Dependence of radar backscatter on coniferous forest biomass. IEEE Transactions on Geoscience and Remote Sensing30, 412-415.
14.
Dutra, L. V. and Huber, R.1999: Feature extraction and selection for ERS-1/2 InSAR classification. International Journal of Remote Sensing20, 993-1016.
15.
Faller, N. P. and Meier, E. H.1995: First results with the airborne single-pass Do-SAR interferometer. IEEE Transactions on Geoscience and Remote Sensing33, 1230-1237.
16.
Fornaro, G. and Franceschetti, G.1995: Image registration in interferometric SAR processing. IEE Proceedings -Radar Sonar and Navigation142, 313-320.
17.
Fornaro, G., Franceschetti, G. and Lanari, R.1996: Interferometric SAR phase unwrapping using Green’s formulation. IEEE Transactions on Geoscience and Remote Sensing34, 720-727.
18.
Fornaro, G., Franceschetti, G., Lanari, R., Rossi, D. and Tesauro, M.1997a: Interferometric SAR phase unwrapping using the finite element method. IEE Proceedings -Radar Sonar and Navigation144, 266-274.
19.
Fornaro, G., Franceschetti, G., Lanari, R., Sansosti, E. and Tesauro, M.1997b: Global and local phase-unwrapping techniques: a comparison. Journal of the Optical Society of America A - Optics Image Science and Vision14, 2702-2708.
20.
Fornaro, G. and Sansosti, E.1999: A two-dimensional region growing least squares phase unwrapping algorithm for interferometric SAR processing. IEEE Transactions on Geoscience and Remote Sensing37, 2215-2226.
21.
Freeman, A.1992: SAR calibration - an overview. IEEE Transactions on Geoscience and Remote Sensing30, 1107-1121.
22.
Gelautz, M., Leberl, F. and Kellerer-Pirklbauer, W.1996: Image enhancement and evaluation: SAR layover and shadows. AEU - Archiv für Elektronik und Übertragungstechnik (International Journal of Electronics and Communications)50, 100-105.
23.
Gens, R. and Van Genderen, J. L.1996: SAR interferometry - issues, techniques, applications. International Journal of Remote Sensing17, 1803-1835.
24.
Goldstein, R. M. and Werner, C. L.1998: Radar interferogram filtering for geophysical applications. Geophysical Research Letters25, 4035-4038.
25.
Goyal, R. K. and Verma, A. K.1996: Mathematical formulation for estimation of baseline in synthetic aperture radar interferometry. Sadhana - Academy Proceedings in Engineering Sciences21, 511-522.
26.
Gray, A. L. and Farrismanning, P. J.1993: Repeat-pass interferometry with airborne synthetic aperture radar. IEEE Transactions on Geoscience and Remote Sensing31, 180-191.
27.
Griffiths, H. D. and Wilkinson, A. J.1994: Improvements in phase unwrapping algorithms for interferometric SAR. Onde Electrique74, 46-52.
28.
Hagberg, J. O., Ulander, L. M. H. and Askne, J.1995: Repeat-pass SAR interferometry over forested terrain. IEEE Transactions on Geoscience and Remote Sensing33, 331-340.
29.
Hilland, J. E., Stuhr, F. V., Freeman, A., Imel, D., Shen, Y., Jordan, R. L. and Caro, E. R.1998: Future NASA spaceborne SAR missions. IEEE Aerospace and Electronic Systems Magazine13, 9-16.
30.
Imhoff, M. L.1995: Radar backscatter and biomass saturation -Ramifications for global biomass inventory. IEEE Transactions on Geoscience and Remote Sensing33, 511-518.
31.
Just, D. and Bamler, R.1994: Phase statistics of interferograms with applications to synthetic aperture radar. Applied Optics33, 4361-4368.
32.
Kasischke, E. S., Melack, J. M. and Dobson, M. C.1997: The use of imaging radars for ecological applications - a review. Remote Sensing of Environment59, 141-156.
33.
Lee, J. S., Hoppel, K. W., Mango, S. A. and Miller, A. R.1994: Intensity and phase statistics of multilook polarimetric and interferometric SAR imagery. IEEE Transactions on Geoscience and Remote Sensing32, 1017-1028.
34.
Lee, J. S., Papathanassiou, K. P., Ainsworth, T. L., Grunes, M. R. and Reigber, A.1998: A new technique for noise filtering of SAR interferometric phase images. IEEE Transactions on Geoscience and Remote Sensing36, 1456-1465.
35.
Lin, Q., Vesecky, J. F. and Zebker, H. A.1992: New approaches in interferometric SAR data processing. IEEE Transactions on Geoscience and Remote Sensing30, 560-567.
36.
Lin, Y. C. and Sarabandi, K.1999: Retrieval of forest parameters using a fractal-based coherent scattering model and a genetic algorithm. IEEE Transactions on Geoscience and Remote Sensing37, 1415-1424.
37.
Luckman, A., Baker, J., Honzak, M. and Lucas, R.1998: Tropical forest biomass density estimation using JERS-1 SAR: seasonal variation, confidence limits, and application to image mosaics. Remote Sensing of Environment63, 126-139.
38.
Lyuboshenko, I. and Maitre, H.1999: Phase unwrapping for interferometric synthetic aperture radar by use of Helmholtz equation eigenfunctions and the first Green’s identity. Journal of the Optical Society of America A - Optics Image Science and Vision16, 378-395.
39.
Madsen, S. N., Martin, J. M. and Zebker, H. A.1995: Analysis and evaluation of the NASA/JPL TOPSAR across-track interferometric SAR system. IEEE Transactions on Geoscience and Remote Sensing33, 383-391.
40.
Madsen, S. N., Zebker, H. A. and Martin, J.1993: Topographic mapping using radar interferometry - processing techniques. IEEE Transactions on Geoscience and Remote Sensing31, 246-256.
41.
Moghaddam, M. and Saatchi, S.1995: Analysis of scattering mechanisms in SAR imagery over boreal forest -results from BOREAS-93. IEEE Transactions on Geoscience and Remote Sensing33, 1290-1296.
42.
Pritt, M. D.1996: Phase unwrapping by means of multigrid techniques for interferometric SAR. IEEE Transactions on Geoscience and Remote Sensing34, 728-738.
43.
Ranson, K. J., Saatchi, S. and Sun, G. Q.1995: Boreal forest ecosystem characterization with SIR-C/X-sar. IEEE Transactions on Geoscience and Remote Sensing33, 867-876.
44.
Ranson, K. J., Sun, G. Q., Lang, R. H., Chauhan, N. S., Cacciola, R. J. and Kilic, O.1997: Mapping of boreal forest biomass from spaceborne synthetic aperture radar. Journal of Geophysical Research - Atmospheres102, 29599-610.
45.
Rignot, E.1996: Dual-frequency interferometric SAR observations of a tropical rain-forest. Geophysical Research Letters23, 993-996.
46.
Rosen, P. A., Hensley, S., Zebker, H. A., Webb, F. H. and Fielding, E. J.1996: Surface deformation and coherence measurements of Kilauea volcano, Hawaii, from SIR-C radar interferometry. Journal of Geophysical Research - Planets101, 23109-125.
47.
Rossi, M., Rogron, B. and Massonnet, D.1996: JERS-1 SAR image quality and interferometric potential. IEEE Transactions on Geoscience and Remote Sensing34, 824-827.
48.
Rufino, G., Moccia, A. and Esposito, S.1998: DEM generation by means of ERS tandem data. IEEE Transactions on Geoscience and Remote Sensing36, 1905-1912.
49.
Sarabandi, K.1997: Delta k-radar equivalent of interferometric SAR’s: a theoretical study for determination of vegetation height. IEEE Transactions on Geoscience and Remote Sensing35, 1267-1276.
50.
Tough, R. J. A., Blacknell, D. and Quegan, S.1995: A statistical description of polarimetric and interferometric synthetic-aperture radar data. Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences449, 567-589.
51.
Treuhaft, R. N., Madsen, S. N., Moghaddam, M. and van Zyl, J. J.1996: Vegetation characteristics and underlying topography from interferometric radar. Radio Science1, 1449-1485.
52.
Trouve, E., Nicolas, J. M. and Maitre, H.1998: Improving phase unwrapping techniques by the use of local frequency estimates. IEEE Transactions on Geoscience and Remote Sensing36, 1963-1972.
53.
Ulander, L. M. H.1996: Radiometric slope correction of synthetic aperture radar images. IEEE Transactions on Geoscience and Remote Sensing34, 1115-1122.
54.
Wang, Z. J. and Li, S. S.1999: Phase unwrapping through a branch-cut-based cut-bridging and window-patching method. Applied Optics38, 805-814.
55.
Way, J., Paris, J., Kasischke, E., Slaughter, C., Viereck, L., Christensen, N., Dobson, M. C., Ulaby, F., Richards, J., Milne, A., Sieber, A., Ahern, F. J., Simonett, D., Hoffer, R., Imhoff, M. and Weber, J.1990: The effect of changing environmental conditions on microwave signatures of forest ecosystems - preliminary results of the March 1988 Alaskan aircraft SAR experiment. International Journal of Remote Sensing11, 1119-1144.
56.
Way, J., Rignot, E. J. M., McDonald, K. C., Oren, R., Kwok, R., Bonan, G., Dobson, M. C., Viereck, L. A. and Roth, J. E.1994: Evaluating the type and state of Alaska taiga forests with imaging radar for use in ecosystem models. IEEE Transactions on Geoscience and Remote Sensing32, 353-370.
57.
Way, J., Zimmermann, R., Rignot, E., McDonald, K. and Oren, R.1997: Winter and spring thaw as observed with imaging radar at BOREAS. Journal of Geophysical Research - Atmospheres102, 29673-29684.
58.
Wegmuller, U. and Werner, C. L.1995: SAR interferometric signatures of forest. IEEE Transactions on Geoscience and Remote Sensing33, 1153-1161.
59.
Wegmuller, U. and Werner, C. L.1997: Retrieval of vegetation parameters with SAR interferometry. IEEE Transactions on Geoscience and Remote Sensing35, 18-24.
60.
Xu, W. and Cumming, I.1999: A region-growing algorithm for InSAR phase unwrapping. IEEE Transactions on Geoscience and Remote Sensing37, 124-134.
61.
Zebker, H. A., Farr, T. G., Salazar, R. P. and Dixon, T. H.1994a: Mapping the world’s topography using radar interferometry - the Topsat Mission. Proceedings of the IEEE82, 1774-1786.
62.
Zebker, H. A. and Lu, Y. P.1998: Phase unwrapping algorithms for radar interferometry: Residue-cut, least-squares, and synthesis algorithms. Journal of the Optical Society of America A - Optics Image Science and Vision15, 586-598.
63.
Zebker, H. A., Rosen, P. A. and Hensley, S.1997: Atmospheric effects in interferometric synthetic aperture radar surface deformation and topographic maps. Journal of Geophysical Research -Solid Earth102, 7547-7563.
64.
Zebker, H. A. and Villasenor, J.1992: Decorrelation in interferometric radar echoes. IEEE Transactions on Geoscience and Remote Sensing30, 950-959.
65.
Zebker, H. A., Werner, C. L., Rosen, P. A. and Hensley, S.1994b: Accuracy of topographic maps derived from ERS-1 interferometric radar. IEEE Transactions on Geoscience and Remote Sensing32, 823-836.
