Integration of Aerial Remote Sensing,Photogrammetry, and GIS Technologies in Seagrass Mapping

Integration of Aerial Remote Sensing, Photogrammetry, and GIs Technologies in Seagrass Mapping

Vanina Pasqualinl, Chistine Pergent-Martini, Philippe Clabaut, Hew6 Marteel, and G6rard Petgent

Abstract surface effects, depth of penetration; Belsher et al., 1988). Con- With a view to implementing a sound management of littoral versely, image processing of normal color aerial photographs plant formations, and more particularly that of seagrass beds, has been successfully used in the littoral environment and, it would appear of interest to test the potentiality of image more particularly, within marine phanerogam seagrass beds processing for various types of photographs (color, infmred, (Kelly, 1980; Walker, 1989; Green et al., 1996; Pasqualini et al., and black and white). The present study was carried out within 1997). Indeed, the littoral environment harbors a vast array of the Gulf of St-Florent (Corsica, France) on a Posidonia complex ecological systems which are extremely diversified oceanica reef platform. Over the last 40 years, no major and productive, such as seagrass beds (Orth et al., 1984; Fortes, diachronic evolution has been observed within this plant 1989). Distributed throughout the planet, these seagrass beds formation. An erosion of the coastline has been noted inland occupy large surface areas (Hartog, 1970) and play a major role of these seagrass beds, however, with erosion values of up to in terms of sedimentology (McRoy and Helfferich, 1980; Fon- 40 m. The use of photogrammetric techniques, which are new seca and Fisher, 1986). In the Mediterranean, the endemic spe- to the marine environment, allows the possibility of obtaining cies Posidonia oceanica (L.) Delile covers a large portion of a numeric model of a given site. The comparison of carto- littoral bottoms, and this from the surface to depths of about 40 graphic and bathymetric data, brought together in a geo- m (Molinier and Picard, 1952).It forms vast underwater mead- graphic information system, allows the spatial distribution of ows but can also, in sheltered areas and at shallow depths, form seagrasses to be evaluated for the first time. homologous structures such as barrier reefs and reef platforms (Molinier and Picard, 1952), thus creating- spectacular- underwater landscapes (UNEP, 1990). Introduction In order to increase our understanding of these seagrass To successfully manage and protect a given natural resource, an beds, a number of techniques, which are usually applied to the exhaustive inventory must be made of the species involved terrestrial environment, were used in the present study to and its geographical distribution. To this end, the techniques examine these shallow-water marine environments. To this incorporating satellite andlor aerial remote sensing, image end, image processing was applied to (1)false-color infrared processing, and photogrammetry were quickly perceived as positive transparencies in order to more easily distinguish being the most appropriate tools (Stretta et d.,1990; Lachow- between the marine plant formations present, and (2) black- ski et al., 1994;French et al., 1995; Cohen et al., 1996; Estreguil and-white photographs in order to follow the temporal evo- and Lambin, 1996; Green et al., 1996; Long and Skewes, 1996), lution of the seagrass beds over several decades. Finally, photo- because they allow the characterization of geographic regions grammetric techniques were used to determine site topogra- which are either very large or not easily accessible (e.g., man- phy, because bathymetric data for such sites are generally groves, mountainous regions, deserts). Thus, the use of infrared lacking, and to evaluate the spatial distribution of the seagrass radiance, obtained from satellite data, allows the accurate beds. mapping of plant formations (Aschbacher et al., 1995),whereas the use of photogrammetry allows the detailed topography of a given site to be determined based solely on the use of aerial Materials and Methods photographs (Fox, 1995). The present study was carried out on the Posidonia oceanica reef formation present in the Gulf of St-Florent (Upper Corsica, The numerous attempts to use image processing of satellite data in the management of benthic marine resources quickly France; Figure 1).This formation is located at the far end of the revealed the limits of these techniques (e.g., pixel size, water gulf, between the Roya rock formation and an artificial dike. This site is subject to moderate hydrodynamic conditions and receives a high level of sediment input due to its proximity to the mouth of a coastal river (the Aliso; Figure 1). The different techniques (image processing, photogram- V. Pasqualini, C. Pergent-Martini, and G. Pergent are with the metry) used were applied to aerial photographs. The different Universit6 de Corse, Equipe c(Ecosyst&mesLittoraux~, B.P. 52,20250 Corte, France ([email protected]). V. Pasqualini is also with the Universit6 de Provence - Centre de St. Jbrome, IMEP, UPRESA CNRS 6116, LBEM, Case 421 bis, Av., Escadrille Normandie Niemen, 13397 Marseille Cedex Photograrnmetric Engineering & Remote Sensing 20, France. VoI. 67, No. 1, January 2001, pp. 99-105. P. Clabaut is at 14 rue P. Doumer, 59 110 La Madeleine, France. 0099-1112/01/6701-99$3.00/0 H. Marteel is at 291 Bd. Clhmenceau, 59700 Marcq en 0 2001 American Society for Photogrammetry Baroeul, France. and Remote Sensing

PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING formed of reflectances for each color of the recorded spectra (Blue-Green Plane, Green-Red Plane, and Red-Infrared Plane] for the false-color infrared positive transparencies, and formed of reflectances for 256 shades of grey (Plane in shades of grey] for the black-and-white negatives. Data analysis was then carried out using the Multiscope software (Version 2.4, Matra Cap System@).A geometrical rectification and the elimination of terrestrial domains was performed for all of the photographs (Pasqualini et al., 1997). For the normal-color aerial photographs as well as the false-color infrared positive transparencies, a principal com- ponent analysis (PCA) was applied to two planes. A classifica- tion supervised by hypercube was applied to the colored composition, and involved positioning polygons assumed to contain pixels belonging to the same assemblage and bottom type (Courboules et al., 1988). The positioning of the polygons was therefore based on in situ field observations. Homogeniza- tion was carried out to eliminate isolated or wrongly classified points of the image. Occasional corrections were made to the final images on the basis of field data (e.g., litter). Following the above pre-processing, the images generated from the black-and-white photographs were subjected to pixel thresholding. This thresholding consists in determining the thresholds or limits for each of the assemblages or bottom types to be examined based on field data. This method allowed a thematic map to be drawn. Figure 1. Location of the study site. Photogrammetry Photogrammetry consists in using the common region of two photographs taken from different angles to rectify those photo- aerial photographs used were normal-color photographs, false- graphs and to determine the altitude fiom which the photo- color infrared photographs, and black-and-white photographs graphs were taken. The technical details involved in the taking (Table 1).False-color infrared positive transparencies were of the photographs (usable surface area, bottom cover, scale, obtained using a film for which the sensitivity to light encom- verticality) in addition to the meteorological conditions passed the entire visible range (400 to 750 nm) as well as wave- (amount of light, visibility) were determined by the Conseil lengths approaching the infrared (750 to 900 nm; Kodak National de l'lnformation Gtiographique (CMG, 1993). The Aerochrome Infrared 50-231). photogrammetric techniques were applied to the normal-color Regardless of the nature of the photograph used, four photographs taken in 1994. The "stereoscopic pairs" were digi- assemblages and bottom types were taken into account: (I) soft tized and processed by computer. This processing involves geo- sediment (mud and sand), (2) photophilous algae on rock metric rectification or transformation on the basis of accurately (including scree and pebbles), (3) continuous seagrass beds of located landmarks. The photogrammetric techniques allow an Posidonia oceanica (presenting coverage greater than 50 per- object or area to be represented in three dimensions. In this cent), and (4) dead "matte" (assemblage of intermingled dead way, a bathymetric survey of the reef formation was produced rhizomes with sediment) or mosaic seagrass beds of Posidonia at a scale of 1:5,000,with a minimum vertical distance of 0.5 m oceanica (on matte, rock, or sand). The collection of field data between the contour lines. was performed by a scuba diver using the transect method (Meinesz et nl., 1981). Depth was recorded along each transect Geographic Information Systems using an electronic depth gauge (Suntom with an accuracy of 10 A numeric field model was generated using the Arc Info soft- cm). ware (Version 7, ESRIa). This model was based on the coverage of the arcs corresponding to thebathyrnetric data and allowed a image Processing slope coverage to be determined. The totality of the carto- Aerial photographs were digitized by means of a scanner graphic data obtained by image processing was vectorized and (Canon CLC 10, driven by a Pentium 100 microcomputer) subsequently repositioned at the same graphic location (Lam- using the Image-In Scan & Paint software (Image In@). Each bert IV) as the bathymetric data. pixel (1 m) in the photograph corresponded to a vector of properties: Results formed of reflectances for each base color in the visible spectrum Mapping ofthe Reef Formation (Red Plane, Green Plane, and Blue Plane) for the normal- Examination of the normal-color shots, whether from 1994 or color photographs, 1996, revealed that the Posidonia oceanica seagrass bed occu-

TABLE1. SPEC~FICAT~ONSOFTHE PHOTOGRAPHSUSER TO CHARACTERIZETHE ST-FLORENTREEF FORMATION Nature of the photos Origin Date Scale - - - Black and White Institut GBographique National June 1960 1:5,000 Black and White Institut Mographique National June 1975 1:3,500 Normal Colors Compagnia Generale Ripreaeseare June 1994 1:6,500 Infrared Colors Compagnia Generale Ripreaeseare June 1994 1:2,000 Normal Colors Institut Gographique National June 1996 1:5,000

100 lanuary 2001 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING pies the totality of the external edge of the reef formation (Fig- and bottoms types, due to the high level of absorption of this ures 2A1 and 281. The center of this formation is essentially type of radiation in the marine environment. Thus, differences occupied by dead matte, which is covered here and there by in interpretationappeared close to the shore between the shal- silty sand, The proportion of the surface area covered by these low water sand bottoms and the photophilous assemblages on last sediments appears to be lower in the map elaborated from rock substrates (Figure 2C). Similarly, in deeper regions, the the 1996 photograph (Figure 2B). Nevertheless, the ability of spedsignature of the sand was similar to that of the dead these soft sediments to hide underlying substrates (rock, matte. Finally, the treatment techniques employed did not degraded seagrass beds), which is a function of both time and allow the heterogeneity of the seagrass bed to be evaluated. the existing hydrodynamic conditions, leads to a modification Indeed, this heterogeneity was often interpreted as an uninter- in their distribution but is not in itself an indication of the alter- rupted structure (Figure 2C). ations undergone by the reef formation. A particular strucime Reatment of the black-and-white photographs taken in can be observed in all of the photographs, located at the lower 1960 allowed the sand bottoms to be distinguished from the con- western part of the reef formation (Figures 2A1, 2A2,and ZB). tinuous Posidonia oceanica seagrass bed, and this despite the Observations of this structure by scuba divers reveal that this fact that the initial contrast of the pictures was low (Figures 3A structure is in fact a large patch of Posidonia oceanica seagrass and 3B). Convsrsely, it was not possible to differentiate bed, of 10 to 12 m in diameter, the center of which is occupied between photophilous assemblages on rock substrates from by dead matte. This original formation represents a "micro- those present on dead matte, nor was it possible to distinguish atoll of Posidonia," such as has been described by Cirik (UNEP, deeper sand bottoms from degraded seagrass beds (Figure 3B1. 19901. This micro-atoll is the first to be described in France, as This created an important level of confusion which subse- analogous formations have only been described in Turkey quently led to an overestimation of degraded seagrass beds at (UNEP, 19901 and Italy (Calvo and Frada-Orestano, 1984). This lower depths [Figure 3B). In light of these limitations, and due type of structure is generally observed at depths of between 0.5 to the poor quality of the available photographs (e.g., specular and 2.5 m. Plagiotropic rhizomes (horizontal) develop in a cen- reflectance, shots of waves), information concerning the distri- trifugal mannex at the edge of the micro-atoll, whereas the bution of assemblages and bottom types could not be obtained shoots die within the circle (UNEP, 1990). for the shots taken in 1975. 'batment of the false-color infrared positive transparencies taken in 1994 generated results which are quite different Tmpoml Evdtltkn of the Reef Formgtian from those obtained &om the normal-color photographs (Figure The tiherations of the reef formation over time can only be stud- 2C). Generally speaking, it would appear that the use of false- ied through the temporal monitoring of the continuous Posi- color infrared positive transparencies causes an overestimation do~aoce(u11'cu seagrass beds. Indeed, the fluctuating nature of of the plant formations at the expense of the other assemblages the soft substrates, as well as their capacity to maak underlying

I Dead matte a m@saicseagwsbed# of Pmidonia oceorica

Figure 2. Thematic maps of the assemblages and bottom types present within the St-Florent reef formation, abtained using image processing of (&) normalcolor photographs taken in 1994; (A2) enlargement of the 'micro-atoll", which corresponds to a large patch of Posidonia oceanica seagrass, the center of which is occupied by dead matte; (6) normakolor photographs taken in 1996; and (C) falsecolor infrared positive transparencies taken in 1994.

PHOTOGRAMMETRIC ENGINEERING 81REMOTE SENSING Seagrass beds ofParidonin oceonica I- Dead mate a mosaic sea~asbeds of Paridonin oceonica Pbotophilars algae on rock I Figure 3. (A) Aerial black-and-white photograph taken in 1960 of the St- florent reef formation. (B) Thematic map of the assemblages and bottom types, obtained using image processing of 1960 photographs.

formations (rocks, degraded seagrass beds), leads to a modifica- assessed (Table 2). It can thus be noted that a decrease in surface tion in the distribution of these substrates which will vary as a area of 0.36 ha occurred between 1960 and 1994, and that a function of both time and the existing hydrodynamic condi- slight increase of 0.7 ha has occurred since this period. tions. Visual examination of the maps drawn up from the photographs taken in 1960 (Figure 3B), 1994 (Figure 2A1), and 1996 (Figure 2B) reveals that the seagrass beds always occupy the ThreeDimenslonal Analysls of the Reef Fonnatlon entire external front of the reef formation. Nevertheless, a few The photogrammetric treatment at the St-Florent site generated differences can be observed. On the map drawn from 1960 data, a bathymetric map of great precision up to a depth of 8 m (Fig- themicro-atoll is not visible, although seagrass beds are present ure 5). Beyond this depth, the diminishing amount of light does to the southeast of the reef formation. These beds are not dis- not allow reliable results to be obtained. The depth contour cernible in later maps. In addition, an important modification lines clearly indicate several shallows, including the central in the position of the coastline can be observed (Figure 4). reef formation, the Royarock formation, and the dike (Figure Indeed, a progressive erosion of the coastline inland of the reef 5). Depth in the center of the reef formation does not exceed 0.5 formation has been occurring since 1960. This erosion has led m, whereas it is over 2 m on either side of it. By superimposing to a 40-m regression of the coastline, which represents a mean the cartographic data generated by image processing of normal- annual regression of 1m. color photographs taken in 1994 and the bathymetric data, it The use of image processing allowed the surface area occu- was possible to determine the three-dimensional aspect of the pied by the continuous seagrass beds to be quantitatively reef platform (Figure 6). It can thus be observed that the continuous Posidonia oceanica seagrass beds are preferentially located where steep slopes exist, whereas dead matte and degraded seagrass beds are generally found in regions characterized by gentle slopes (Figure 7).

Discussion and Conclusion The use of image processing in the examination of several types of photographs allowed the inherent limits of each of these mediums to be evaluated. Although the constraints remain comparable, in terms of both the quality of the photographs (contrast, absence of visual artefacts) and the precision of the field data [number, distribution), the potentialities differ as a function of the nature of the shots (black and white, color). Image processing of normal-color photographs allowed an accurate map of the St-Florent reef formation to be drawn up (Figures 2A1 and 2B). This type of processing is thus more appropriate for the elaboration of detailed environmental maps than is the method using false-color infrared positive transparencies. The major advantage of these last photographs is that they optimize the detection of marine plant formations Figure 4. Alteration of the coastline, such as Posidonia oceanica seagrass beds regardless of just inland of the St-florent reef for- whether these form continuous beds or are present as mosaics. mation, from 1960 to 1996. Indeed, the use of infrared is particularly appropriate to visual- ize marine plants growing at shallow depths and, in particular,

102 January 2001 PHOTOQRAMMETRIC ENGINEERING & REMOTE SENSING TABLE2. CHANGESIN THE SURFACEAREA OCCUPIED BY CONTINUOUSPOSILWNIA OCEXNlCA SEAGRASSBEDS WITHIN THE ST-FLORENTREEF FORMATION, BETWEEN 1960 AND 1996 Year 1960 (Black and White) 1994 (Normal Colors) 1996 (Normal Colors) Surface Area (ha) 2.39 2.03 2.10

N t + @+ +

Land w Soft sediment Seagrass beds of Pmidoni~oceonic Wad matte or mosaic seagrass beds of Paridonin oceanico I Phnophilous algae on mck -0 40m Figure 6. Three-dimensional representation of the assem- Figure 5. Bathymetric data of the St-Florent reef formation, blages and bottom types present within the St-florent reef obtained using photogrammetry. formation.

where sand is present (Welch and Remillard, 1988).Neverthe- less, in light of the important absorption of this type of radia- 90.00 tion, their utilization in the marine environment remains Seagrass beds PI 80.00 / limited to solely shallow regions and therefore, in these Dead mate or mosaic / regions, represents a valuable tool in the detection of Posi- "" seagrass beds / donia oceanica seagrass beds. comparison between the results obtained through image processing (Figures 2A, and 2B) and an existing map of the St- Florent reef formation generated using the orthophotoplane method (Figure 8A; Pasqualini, 1997) reveals that the observed distribution of the formations remains relatively similar 20.00 between these two methods. The drawbacks associated with the utilization of photointerpretation, however, include a high 0.00 level of operator subjectivity and a high implementing cost - (from a time-budget point of view) as compared to the image processing method. In addition, the methods involving the image processing of photographs allows the user to modify the basic pixel size as a function of the study goals and the surface area to be examined. The basic pixel size adopted is a determi- Figure 7. Diagram representing the distribution of the nant factor in the precision of the map generated. Indeed, the assemblages and bottom types (expressed as percentages use of image processing in the analysis of SPOT satellite images of the surface area) present within the St-Florent reef forma- (ground pixel size of 20 m in multispectral mode or 10 m in pan- tion, as a function of the slope. chromatic mode) is in itself an important limitation, in particu-

PHOTOGRAMMETRIC ENGINEERING 81 REMOTE SENSING lanuary 2001 103 Rgure 8. Thematic map of the assemblages ahd bottom types present within the St-Florent reef formation obtained using (A) the orthophotoplane method which makes use of two color photographs (as described by Pasqualini (1997)),and (8)the treatment of spot images (as described by Koudil (19931).

lar where detailed maps of small structures are required (Figure coastal installations (Paskoff, 1985). The construction in the 8B; Koudil, 1993). early 1970s of the port of St-Florent, located at the mouth of the The use of image processing in the analysis of black-and- Aliso, probably led to a decrease in the levels of alluvial river white photographs presents the advantage of allowing old data input and was thus a determinant factor in the evolution of the to be exploited while at the same time decreasing the problem coastline. of operator subjectivity. The absence of field data in this analy- Photogrammetry, which is only rarely used in the marine sis, however, means that only the mapping of continuous Posi- environment, thus represents a highly efficient tool. Indeed, it donia oceanica beds is possible (Figure 3B). The exploitation allows detailed bathyrnetric maps to be drawn up quickly for of black-and-white photographs through the use of image pro- that strip of coastline present at depths of between 0 and 10 m. cessing therefore represents an indispensable mapping tool in Its value is increhsed by the fact that these areas are often inac- monitoring the evolution of benthic assemblages over time. cessible using other more classical techniques (e.g., depth The diachronic analysis of the reef formation, which was sounder). These data allow the spatial configuration of the St- based on the temporal monitoring of continuous Posidonia FIorent reef formation to be visualized (Figure 6). The continu- oceanica seagrass beds, revealed that no major modifications ous Posidonia oceanica seagrass beds are essentially located in had occurred within this formation since 1960 (Figures 2 and those areas where a steep slope is present, i.e., at the external 3), despite the fact that surface area covered by these continu- edge of the reef formation (Figure 7), whereas the central ous seagrass beds was seen to decrease slightly between 1960 regions of this formation, characterized by gentle slopes and and 1994 (Table 2). The 1960 map, however, reveals the past shallow waters, are mainly occupied by dead matte. Originally, presence of continuous seagrass beds to the southeast of the this plateau was probably formed close to the beach through reef formation, beds which subsequently disappeared (Figure the growth of orthotropous rhizomes (vertical), which were 3). Although it is difficult to claim the unquestionable certi- favored by important levels of sediment input. The evolution- tude of these observations, due to the different techniques ary dynamics of this reef formation, as experienced by the fron- employed, they would appear to be corroborated by the fact tal regions, thus progressed towards the open sea, eventually that the eastern front of the reef formation is the most exposed leading to the characteristic triangular formation observed to sediment inputs from the Aliso River. The reef formation is (Boudouresque ef al., 1985). In conclusion, it would appear thus directly subjected to degradation of natural origin linked that photogrammetric techniques, associated with geographic to the episodic floods experienced by the river, the mouth of information systems, represent a promising means of assessing which is situated towards the east. Following the extensive the spatial distribution of seagrasses and may thus prove floods of November 1994, scuba divers noted the partial burying invaluable in the protection and management of coastal of Posidonia oceanica shoots by silty sediment at the edge of regions. the reef formation. In addition to the alterations brought to the assemblages and bottom types, an erosion of the coastline of Acknowledgments over 40 m in 36 years was also observed just inland of the reef The authors wish to thank M. F. Cuq, the head of the CNRS "G6o- formation (Figure 4). The 1990 and 1996 coastlines appear to be syst8mes" laboratory in Brest (France), for having put the Arc slightly different from that recorded in 1994, probably due to Info software at our disposal. variations in the tidal amplitude. These variations can lead to discrepancies of several meters in the position of the coastline, References especially in areas which are relatively flat such as the St- Florent site. Although the detection of such a coastal erosion is Aschbacher, J., R. Oken, J.P. Delsol, T.B. Suselo, S. Vibulsresth, and T. Charrupat, 1995. An integrated comparative approach to man- not in itself an exceptional occurrence, indeed a generalized grove vegetation mapping using advanced remote sensing and GIs retreat is observed for almost all beaches of the French coastline technologies: Preliminary results, Hydrobiologia, 295(1-3): (Paskoff, 1985), this retreat appears to be relatively rapid for 285-294. this region of the Mediterranean. Indeed, the only other retreat Belsher, T., A. Meinesz, J.R. Lefevre, and C.F. Boudouresque, 1988. of this magnitude to have been recorded along the French Med- Simulation of Spot satellite imagery for charting shallow water iterranean coast is at the mouth of the Rhane River, and is most benthic communities in the Mediterranean, Marine Ecology, probably due to a decrease in sediment input as the result of P.S.Z.N.I., 9(2):157-165.

PHOTOQRAMMETRIC ENGINEERING & REMOTE SENSING Boudouresque, C.F., A. Meinesz, and J.R. Lefevre, 1985. Cartographie Florent. MBm. DESS TBlBdBtection. Ecole Nation. Sci. GBograph., des peuplements benthiques marins de Corse: I. La formation Univ. Paris VI, France, pp 1-20. r6cifale B Posidonia oceanica de Saint-Florent, Ann. Inst. Lachowski, H.M., T. Wirth, P. Maus, and P. Avers, 1994. Remote sensing ocBanogr., 61(1):27-38. and GIs - Their role in ecosystem management, J. Forest., Calvo, S., and C. Frada Orestano, 1984. L'herbier B Posidonia oceanica 92(8):39-40. des cdtes siciliennes: les formations rBcifales du Stagnone, Inter- Long, B.G., and T.D. Skewes, 1996. A technique for mapping mangroves national Workshop Posidonia oceanic0 Beds, (C.F. Boudouresque, with Landsat TM satellite data and geographic information sys- A. Jeudy de Grissac, and J. Olivier, editors), 12-15 October, Por- tem, Estuar. Coast. Shelf Sci., 43(3):373-381. querolles, France, GIs Posidonie publ., Marseille, France, 1:29-37. McRoy, C.P., and C. Helfferich, 1980. Applied aspects of seagrasses, C.N.I.G., 1993. Proposition de sp6cifications g6n6mles pour les prises Handbook of Seagrass Biology: An Ecosystem Perspective (R.C. de vues a6riemes destinkes d des lev6es photogramm6triques Phillips and C.P. Mc Roy, editors), Ed. Garland STPM Press, New r6guliers, Centre National de I'information Gographique, (C.N.I.P. York, N.Y., pp. 314. Ed.), France, pp. 1-12. Meinesz, A., M. Cuvelier, and R. Laurent, 1981. MBthodes r6centes de Cohen, W.B., J.D. Kushla, W.J. Ripple, and S.L. Garman, 1996. An cartographie et de surveillance des herbiers de phanBrogames introduction to digital methods in remote sensing of forested marines. Leurs applications sur les cates fian~aisesde la MBditer- ecosystems: Focus on the Pacific Northwest, USA, Environ. Man- ranBe, Vie Milieu, 31(1):27-34. age., 20(3):421-435. Molinier, R., and J. Picard, 1952. Recherches sur les herbiers de PhanCo- Courboules, J., R. Maniere, and C. Bouchon, 1988. Systbme d'inform- games marines du littoral mBditeman6en franqais, Ann. Inst. ations gBocod6es et tBl6dBtection B haute r6solution. Exemple oc6anogr., 27(3):157-234. d'application aux cdtes jordaniennes, Oceanologica Acto, Orth, R.J., K.L.J. Heck, and J. Van Montfrans, 1984. Faunal communities 11(4):337-351. in seagrass beds: A review of the influence of plant structure and Estreguil, C., and E.F. Lambin, 1996. Mapping forest-cover disturbances prey characteristics on predatory-prey relationships, Estuaries, in Papua New Guinea with AVHRR data, Journal of Biogeogm- 7:339-350. ph~23(6):757-773. Paskoff, R., 1985. Les littoraux. Impact des am6nagements sur leur Fonseca, M.S., and J.S. Fisher, 1986. A comparison of canopy friction 6volution, Collection gbographie, Masson Bdit., France, 190 p. and sediment movement between four species of seagrasses with Pasqualini, V., 1997. Camct6risation des peuplements et types de fonds reference to their ecology and restoration, Mar, Ecol. Prog. Ser., le long du littoral corse (Mbditemnhe, France), These Doct. ((Eco- logie marine)),Univ. Corse, France, 190 p. 29:15-22.- -- -- Fortes, M.D., 1989. Seagmsses: A Resource Unknown in the ASEAN Pasqualini, V., C. Pergent-Martini, C. Fernandez, and G. Pergent, 1997. Region, ICLARM Education Series 5, Philippines, 46 p. The use of airborne remote sensing for benthic cartography: Advantages and reliability, Int. J. Remote Sensing, 18(5): Fox, A.J., 1995. Using multiple data sources to enhance photogramme- 1167-1177. try for mapping Antarctic terrain, Polar Research, 14(3):317-327. Stretta, J.M., M. Petit, and M. Simier, 1990. Integration de la tBlBd6tec- French, N.H.F., E.S. Kasischke, L.L. Bourgeauchavez, and D. Berry, tion a6rospatiale dans la base de dom6es d'un expert dBdi6 B la 1995. Mapping the location of wildfires in Alaskan boreal forests pQhe thonibre. Halieutique, ocBanographie et tB16dBtection, Bull. using AVHRR imagery, Int. J. Wildland Fire, 5(2):55-62. Inst. Oc6an., Monaco, N" Sp. 6, pp. 199-207. Green, E.P., P.J. Mumby, A.J. Edwards, and C.D. Clark, 1996. A review UNEP, 1990. Livre rouge "G6rard Vuignier" des v&gBtaux,peuplement of remote sensing for the assessment and managen@l of tropical et paysages marins menac6s de M6ditermnb. UNEPIIUCNI GIs coastal resources, Coast. Manag., 24(1):1-40. Posidonie, UNEP, MAP Technical Reports publ. 43, France, 250 p. Hartog, C. Den, 1970. The seagrasses of the world. Verhand. Koninklijke Walker, D.I., 1989. Methods for monitoring seagrass habitat, Proceed- Nederl Akad. Wetenschap Afd. Nat. Tweede reeks, North-Holland ings Rep. Workshop, 20-22 June 1988, Melbourne, Australia, Publ. Amsterdam, 59(1):1-272. VIMS Working Paper 18, pp. 1-26. Kelly, M.G., 1980. Remote sensing of seagrass beds, Handbook of Sea- Welch, R., and M. Remillard, 1988. Remote sensing and geographic grass Biology: An Ecosystem Perspective (R.C. Phillips and C.P. information system techniques for aquatic resource evaluation, Mc Roy, editors), Garland STPM Press, New York, N.Y., pp. 69-86. Photogrammetric. Engineering b Remote Sensing, 54(2):177-185. Koudil, M., 1993. Cartographie biosddirnentaire des petits fonds marins (Received 11 February 1999; accepted 11 October 1999; revised 13 par imagerie SPOT en MBditerranBe. Golfes de Calvi et de St January 2000)

Read PE&RS on-line! Grids & Datums Excerpts of PE&RS are now Abstracts available on-line.,. Software Review Calendar Plus, stay tuned for Classifieds many more advances to the Book Review ASPRS web site. and many more prs. org

PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING January 2001 105