Remote sensing for resources development and environmental management: Remote sensing for resources development and environmental management

Damen, M. C. J.

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Multivolume work

Persistent identifier:: 856342815

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856342815

Language:: English

Additional Notes:: Volume 1-3 erschienen von 1986-1988

Editor:: Damen, M. C. J.

Document type:: Multivolume work

Volume

Persistent identifier:: 856343064

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Scope:: XV, 547 Seiten

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856343064

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(26,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Damen, M. C. J.

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: 2 Microwave data. Chairman: N. Lannelongue, Liaison: L. Krul

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: Shuttle imaging radar response from sand dunes and subsurface rocks of Alashan Plateau in north-central China. Guo Huadong, G. G. Schaber & C. S. Breed, A. J. Lewis

Document type:: Multivolume work

Structure type:: Chapter

d covering, euiate-mottled k usually nas tion direction tne radar osed of tde c aunes witn ig. 3). No rea. The e with the IR-A radar's and illumi- angles be- crientation b, and c are ysis of Yama- B # Type of D* aunes ° crescentic some star crescentic ’ **crescentic some star outcrops sand tion beam and lluminated on ana there- pe of sand e angles be- ion and slip- a 30° angle ing radar of the slip- ong return, a b) tne radar of the slip- n results. Section c, the s slopes turn is ex- idai-snaped his study f radar re- e can conclude t a maximum ce orientation ating radar t the two dune f the Yapulai Mountains t-LOn and for cated to the referred to e otner side ver, the two net deserts he nortneast esert and the part of Teng- across the s the north- tains and de- he N30°E di rection parallel with the mountain trend. As expected the dunes formed by these re-directed winds are oriented to the N30 e E are different from the main SE oriented dunes of the Badain Jaran Desert. These are NW dunes mentioned above. The SE dunes referred to above are also crescentic dunes. The prevailing north west winds control the direction of aeolian transport and therefore the orientation of the slipfaces is S50°E (Fig. 4b). SIR-A radar image (Fig. 4&) shows that NW dunes have dark response and SE dunes have bright-point return. Respectively, these are similar to Section c and a of the Yamalik Dunes. Analysis of Landsat images indicates that the characteristics of Yapulai Shan and Yamalik Dunes are very similar. Both dune fields have crescentic dunes and there is no vegetation cover in the active dune area. Therefore the radar imaging mechanism is the same. The NW dune slipfaces are away from radar beam and exhibit no return. The SE dunes in which the angle between radar beam and long axes direction is about 60® produce a bright-point signature. 3.3 Badain Jaran Desert Badain Jaran Desert, located in western Ala- shan Plateau (See Fig. 1), has an area of about 44>000km . Most of the sand dunes or "sand mounds" in this desert are very high, averaging 200-300 m in height with an occa sional dune more than 500 m high. These dunes are reported to be the highst in the world. The crest-to-crest spacing of the dunes is approximately 3 km. Effective winds in this desert, as mentioned in the last chapter, are mainly from the northwest. Fine grained sand form the com pound crescentic dunes--the main type of dunes in this area. Smaller secondary crescentic shaped dunes on the stoss slopes are common. Vegetation is very sparse. Lakes developed in interdune areas are runned with vegetation, mainly reeds and marsh grass. Linear align ment of these interdunal lakes, as noted on Landsat and SIR-A, suggests structural con trol. SIR-A radar image of east-central Badain Jaran Desert shows a large area of highly contrasting return (Fig. 5&)• Three different kinds of radar return patterns have been identified. They are as follows: 1. Short curvilinear return pattern. The long axes of the return patterns are parallel to the radar flight direction (perpendicular to radar illumination direction). This is the most promonent radar return pattern in the study area; 2. Small bright point patterns. They are similar to the pattern in Sections a and b of the Yamalik Dunes and the SE dunes of Ya pulai Shan Dunes. This small bright point pattern is generally found distributed in the area between two dune crests; and 3. Circular bright return patterns. These large dunes of the Badain Jaran De sert are clearly shown on Landsat MSS ima gery (Fig. 5b). The Landsat indicated that the long axes trend of the dunes is NNE and the slipface orientation is SSE. This sug gests that information about the dunes inter preted from SIR-A imagery is incomplete. Com parison of the SIR-A image with Landsat of the same scale indicates that the tnree dif ferent-kinds of return patterns have different origins. The short curvilinear return pattern results from radar reflection from the sand dunes' slipfaces oriented toward the radar illumination source e.g., soutn facing slip- faces have bright return in tnis area. The sand slipfaces not facing toward tne radar source have no return. The small bright point pattern appears to be radar return from se- conaary dunes slipfaces oriented towards the radar beam. The size of these secondary dunes is comparable to tne secondary dunes in the Yamalik dune field and therefore have a si milar radar return pattern. The vegetation around the intertunal lakes, reeds and marsh grass, have a nigh complex dielectric con stant and surface roughness, resulting in a very bright return from around the rim of lake. 4. SIR-B RESPONSE FROM SaND DUNES SIR-B radar which works more effectively is developed basea on the SIR-A. Table 2 snows the different cnaracteristics between, the two radar systems. It can be seen from the table that tne frequency and polarization of the two systems are same but the looking angle and data record method are different. Table 2 Comparison between SIR-A and SIR-B. Characteristics SIR-A SIR-B Altitude 260 km 352, 274, 225 km Wavelength 23.5 cm 23.5 cm Polarization HH HH Looking angle 47° 15-60° Swath width 50 km 20-50 km Range resolution 40 m 14-46 m Arimuth resolution 40 m 20-30 m Data record optical digital & optical SIR-A only has one looking angle, i.e., 47° while SIR-B looking angle changes from 15° to 60° . This advantage means that an optimum looking angle image can be selected. The range resolution, swath width, ratio of signal and noise and dynamic range will vary with tne change of the looking angle. The range resolution may be improved. For ex ample, the range resolution can increase from 40 m of SIR-A to 20 m of SIR-B. Another advantage is that SIR-B provides digitally processed images. All digital data acquired by SIR-B being sent to the ground through the TDRS Ku-band antenna. It is significant that SIR-B flight di rection is approximately parallel to the longitude over the north of China. This di rection is perpendicular to SIR-A direction, which orbited along the latitude. That is, the radar beam direction of SIR-A and SIR-B is perpendicular. These two orbits cross in Shuangjinzhi region to the east of Yamalik Dunes. The Yamalik Dunes are developed along a valley, like a sand river flowing from west to east. In the east end, the Shuangjinzhi area, the windblown sands begin to reduce because of influence of the NNE strike Lang- shan Mountain. The sands form a sand sheet and it is very smooth on the surface. About 15 kilometers far away from the Longshan Mountain, the sands form again the crescentic dunes and the slipface orientation is S60°E. These features can be easily recognized on the digital processing MSS imagery. Like the sand sheet to its west, DN value of the Shuangjinzhi crescentic dunes tend to the minimum on SIR-A radar imagery and does not have any indication of dunes (Fig. 6a). 139

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