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:: 856641294

Title:: Remote sensing for resources development and environmental management

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

Scope:: IX Seiten, Seiten 551-956

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A,. A. Balkema

Identifier (digital):: 856641294

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(26,7,2)

Language:: English

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

Editor:: Damen, M. C. J.

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

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:: 7 Human settlements: Urban surveys, human settlement analysis and archaeology. Chairman: W. G. Collins, Co-chairman: B. C. Forster, Liaison: P. Hofstee

Write comment:: Wegen zu enger Bindung kommt es teilweise im Original zu Textverlust.

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: Automatic digitizing of photo interpretation overlays with a digital photodiode camera: The ADIOS system. C. A. de Bruijn & A. J. van Dalfsen

Document type:: Multivolume work

Structure type:: Chapter

Ltized is the lat has been ssible to re the ?hotos should led in a and displayed tep is to the CRT lines iter those ides on the displayed on the centro!ds tizer together or automatic software will area with the red map on the terpreter. tig areas and ecting the ing it, or by y be sent to g the e considered ’s electronic g is 512 x 512 CCD’s 2048 x ced in 1986 x 3500 , but acy as yet. Is and, like wfinder for ems have the summarizes BIT fair 1986 color OCR RGB RGB haracter on a SPATIAL deo digitizer esolution of 0.3 mm y lower than .1 to 0.025 mera has been otodiode array ) that moves tween the each photodiode is converted into a digital value having up to 12 bits and the information is passed to the computer, as parallel data (DWYER, 1985). Solid state array sensors have excellent geometric properties that are a direct consequence of the photolithographic method of fabrication. (NAGY, 1981). Eikonix claims a spatial precision of 1 pixel, corner to corner. This has not yet been verified, but ITC plans to do a full calibration of its digital camera in the near future. The system at ITC includes further a normalizer board to compensate for individual diode characteristics and a computer driven color filter wheel enabling color separation. (Another Eikonix model uses a 4096 linear CCD array. The CCD however catches less greylevels and is less sensitive to color. A similar CCD camera is manufactured by Datacopy and was used by Chrisman in his earlier cited project.) Using the 2048 pixel camera on a 9 inch airphoto overlay means scanning with a resolution of 9 pixel per mm or about 0.1 mm which is acceptable for a 0.3 mm line width and compares favourably with the effective accuracy of usual manual digitizing. 5.3 The current pilot system Fig 3 gives an overview of the system as it is currently applied. The total system configuration used for ADIOS consists of the Eikonix camera, a PDP 11/24 and an AED 767 graphics terminal with 8 bitplanes. For the experiments photointerpretation overlays are used (fig. 1) that were made by H.T.J. Lutchman in 1980 for a landuse change study (DE BRUIJN, 1981). They are typical for the output of such studies and were indeed made before there was any question of automatic digitizing. Hence it is expected that results obtained with those overlays will be representative for routine operational situations. The various steps of the procedure are as follows: Step 1 scanning In scanning the overlays a red filter has been used to eliminate some red wax pencil lines also present on the overlays but not relevant for the landuse interpretion. The filter reduces effectively the values of the red lines but they do not disappear completely and return to a certain extent after the edge enhancement in step 2. Step 2 edge enhancement and thresholding Although the scanned image looks quite good when displayed on the screen the numerical values of the pixels are affected considerably by - unequal lighting - varying density of overlay paper - varying line intensity and width In the present provisional setup a simple amateur photographers reprostand lighting system with 4 incandescent 60 watt bulbs is used and it has been found that lighting varies indeed considerably. Some of the darker white areas have values below those of some of the black lines in the lighter areas on other scanlines. The values in the unprocessed scanfile vary approximately from 50 (dark lines) to 200 (light paper). When simple thresholding is applied the lines loose their connectivity or the white areas will get a lot of noise, (fig.4) To "reconstruct" the linework a 3 x 3 px edge enhancement filter is used with the following weight factors 1 1 1 1-8 1 1 1 1 On the resulting values a threshold is applied to separate the lines+noise from the paper; in this example: black (lines+noise) 1 40 while (paper) < 40 Step 3 separation of boundary lines and noise Remaining noise and written landuse codes are now separated from the boundary lines using an AED polygon fill command. The cursor is moved on to point on a line and a polygon fill command to color the black line red is given. Eventually all lines connecting to that point will be colored red while disconnected linegroups, codes and noise remain black. In this stage gaps can be edited and the result is a bitmap of the boundary lines only. Ideally all pixels of the boundary lines should form a connecting network (except for the island polygon boundaries). To apply the AED polygon fill it is however important that this connectivity is in the form of "edge-connectivity", i.e. connected pixels should have at least one edge in common. To ensure this condition, a special 2x2 "edge connectivity" operator is applied prior to the actual separation. This operator recognizes cases of pixels that are only connected by one corner and adds an additional pixel to ensure that the pixels will be edge connected. The principle and some results of this operator are shown in fig. 6. Step 4 digitizing fiducial marks Fiducial marks are digitized with the AED cursor and their locations are stored to serve as reference point for later geocorrection procedures. Step 5 entering land use codes The operator can now enter the landuse codes by pointing with the cursor to an area, reading on the screen the (black) handwritten landuse code that was scanned together with the lines, and entering that code via the keyboard or a screen menu. The AED boundary fill is then used to give all pixels in the polygon the relevant landuse code. The operator can follow this as the polygon will be filled with the appropriate landuse code on the screen. In this interaction color is essential to minimize coding errors. Results of the polygon encoding are shown in fig. 7. An alternative is to digitize landuse centroids on a normal manual digitizer and use these points to fill the polygons. This could be an off line or an interactive procedure and further tests will have to show which method will be the most efficient. Step 6 editing The same applies to editing procedures. Gaps and other mistakes may be corrected in step 3 or in step 5 when a "leaking" polygon is detected. Depending on error types and user experience it may be preferred to correct the overlay and rescan it, rather than go through tedious editing procedures. On the other hand minor errors may be edited quicker and easier at the screen, while also a certain amount of automatic error correction may be carried out especially in cases where map contents and topology are well defined.

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