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

Damen, M. C. J.

Bibliographic data

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:: 1 Visible and infrared data. Chairman: F. Quiel, Liaison: N J. Mulder

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: New approach to semi-automatically generate digital elevation data by using a vidicon camera. C. C. Lin, A. J. Chen & D. C. Chern

Document type:: Multivolume work

Structure type:: Chapter

53 ;ween two points P Lmum length of all ) within the resel. r line, and dotted 1 the resel. The am length of all 2 line segments are it with 45°. j-n=0 s of the (i-m) and D ) and (j-n) are not distance. For easy o let J=3 and 1=2. adjacent points P k-). The length of ^(Pi .P i+1 )- The ints P,Q within a paths within the ig.3). e which delineates point on Z. The Q within the resel •(Q.P) in to the bordering ¡ome closed contour it. Let denote 1 elevation values or point P of this different E's which is of the effective distance. That is, if D(P,Z i)<D(P,Z 2 )^D(P,Z 3 ) then Z x and Z 2 are chosen, provided that Ei 35E2 . However, if Ej^ =E 2 then Z3 shall be chosen in stead of Z 2 , and so forth. The interpolated elevation value at P is then E.xW(P,Z.¡)+E xW(P,Z E(P) ^ (1) W(P,Z i )+W(P,Zj) where Z^ and Z- are the chosen curves. The weighting function W(P,Z) can be any monotonously decreseing function of D(P,Z). We use W(P,Z)= 1/D(P,Z) Some of the resels may be surrounded by a single closed contour line to represents a local extreme of a terrain, or located between an open contour line and the edge of the image. In either cases, the above equation cannot be applied because two different E's can not be found for such a resel. For simplicity, we can fill up these resels with the same elevation value, thus create some flat plateaus or valleys. Or, we may, by adding a "peak point" in the resel during the last two steps of the prepocessing, creat an artificial peak point for this resel. The above interpolation equation can be applied again. 5. A fast algorithm for finding D's and E's In a image of size N M, each pixel can be denoted by a pair of integers(i,j), with Ki<N and l<j<M. With the chosen W(P,Z)=1/D(P,Z)»Equation (1) in the last section may be rewritten as: e a(ì. j) d b( ì > j)D A (i, J) E(i, j)= ? -- (2) D A (i, j)+%(i, j) Subscript A(or B) indicates that E A (or Eg) and Da(or Dg) associate with the contour line Z A (or Zg). For fast computation, a "scanning and revising" method is derived to determine these two pairs of D's and E's. For the sake of simplicity, only the essential features are described below. (1) Initiation: For each pixel on the contour line, let D^=Dg=0 and E A =E B =elevation value of the contour line. For each pixel not on the contour line, let D.=Dg=some large number, say M+N, and E A =E B=° Fig. 4. The center square represents the current pixel. The squares (1), (2), (3) and (4) are used for the "forward" scanning and revising. The squares (5), (6), (7) and (8) are used for "backward" scanning and revising. (2) Forward (left-and-down) scanning and revising: Pick up the pixels one by one in the sequence (1,1), (2,1), (N,1), (1,2), (2,2) (N,M). For a given pixel(i,j), E A , Eg, D A and Dg are revised according to following rules: Rule(i):If D A (i,j)=Dg(i,j)=0, then the pixel is on the contour line, no revision is enacted. Rule(ii):If D A (i,j) and Dg(i,j) are nonzero, the original pairs, D A (i.j), E A (i,j),Dg(i,j),Eg(i,j) are to be compared with other 8 pairs of E's and D's. They are calculated from 4 pixels adjacent to (i,j) (see Fig.4) D A (i-l,j-l)+3; E A (i-l,j-1) D B (i-l,j-l)+3; E B (i-l,j-1) D A (i,j-1)+2; E A (i,j-l) D B (i,j-l)+2; E B (i,j-l) D A (i+l, j-l)+3; E A (i+1,j-1) DßCi+l » j~l)+3; E B (i+l, j-1) D A (i-l, j)+2; E A (i-1, j ) D B (i-l,j)+2; E B (i-l,j) However, if any of the indies is outside the range (i.e., i-l=0, j—1=0 or j+l>M), the corresponding pair does not exist. Also, if both DA(i-l,j)=0 and D A (i,j-l)=0, the pairs computed from the pixel (i-1, j-1) shall be disregarded, because (i—1,j—1) and (i,j) will belong to different resels. Rule(iii): Among these pairs, if all the E's are equal, select two pairs with least D's to be the new D A (i,j), E.(i,j) and Dg(i,j) , Eg(i,j). If the E's are not all equal, select the two pairs with least D's and different E's to be the new D A (i,j), E A (i,j), Dg(i,j), Eg(i,j). (3) Backward scanning and revising: This is the same as (2), except the scanning sequence is exactly the opposite and the 4 comparing pixels are a mirror image of above as shown in Fig. 4. (4) The forward and backward scanning cycles may be repeated until no revision occurs. Unless the image contains some resels of unusual (whirling or wriggling) shapes, two or three cycles are sufficient to terminate the process. To examine the feasibility of implementing the algorithms discussed in the previous sections, we select a 10cm x 10cm section out of a topomap sheet with the scale of 1/50,000. The region chosen covers Te-chi Reservior and high mountainous terrain with local peaks around 3000 meters in altitude. The complexity of the topography is particularly suitable for demonstration. Fig. 1, shown in section 2^, represents the line- drawn contour map to be digitized and interpolated. Aside from isolated peaks and water surface, typical interval between two adjacent contour lines is 100 meters. Following the preprocessing steps described in Section II, we obtains a labeled contour-line map with different colors representing different elevation value as depicted in Fig. 5. The final result, followed by the interpolation scheme discussed in Section IV, is illustrated in Fig. 6. The color scale is shown on the right side of the figure, with red (or purple) color for highest (or lowest) elevation level. The color contour lines are superimposed in the figure for comparisons. In a complicated terrain like this example, we are able to demonstrate the capability of our algorithms to generate a digital elevation model.

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