International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
/| 3.2 Built-up area 33
(ii) --> not matched / /
/ / As far as the Built-up area is concerned, small build-
/ > ings are treated differently, and considered alone in Resu
7 the first phase: buildings detected as points or lines nes €
/ are first considered as potential match for small build- umn
Y (ii) - matched ings. They are projected and the closest small build- the
// ings are found. In the case of more than one point tal si
(iii) 7 lying close to a small building, only the closest will umn
be considered as matched. In the case of lines, the p
Figure 3: Road network matching: line match ; parts of the lines lying to far away from the small coul:
buildings are ignored if they are small, otherwise, of th
First the road detected as lines are matched to line they are kept in the set of non-matched detected el- sum
segments of the DB as illustrated in figure 3: (1) the ements. refer
detected road segments are projected, and the close : then
DB line elements are found; (ii) if the line orienta- — Figure 5 shows the results of matching points and
tion match within +/- 10 degrees, and the distance lines on part of the DB: detected elements are dis-
between the segments is lower than 10m the seg- played m blue, while matched and mivsed DB build-
ments are associated; (iii) if the projected segment ~~ "85 ar€ displayed in green, and red respectively.
covers only part of a DB segment and if the remain- -
ing DB segment is smaller than 10m, that remain- o est .
ing part is considered as detected as well; (iv) all X . i t S
detected segments without associated DB segment
are considered as false alarms. ] 1]
Tabk
Then, the road detected as polygons are consid- a L Cr Sub-
ered as illustrated in figure 4: (i) the polygons are c
projected (in orange), dilated and filled (in blue);
(up ns Femaimre DB Seeme nts are projects on Figure 5: Matching BUA; in blue: detected build-
the latter and dilated; (iii) parts outside the dilated . ‚€ : :
s gd A le ings noted as points and lines; in green: matched
polygons are considered as not matched (in red) un- A: MM
less they are too small; (iii) remaining large uncov- DB builds; Hi reds missed DB Gwldinss
y g larg
ered polygon parts are considered as false alarms.
Both the remaining elements of the DB and the de-
tected polygons are projected. The DB polygons Table
polyg proj polyg
that are covered by more than 80 % of its surface by Wa
a detected polygon are considered as totally seen,
otherwise, each of its connected parts is analyzed:
if it represents less than 10 % of the total area, it is Thes
ignored, otherwise it is kept in the unmatched part resul
of the DB. Similarly, the connected parts of the de- than
: tected polygons lying outside the DB polygons are sub-ı
Figure 4: Road network matching; left: detected ^ analyzed: if they represent more than 10 % of the more
polygons in orange, dilated and filled polygon in total detected polygon, they are considered as false 13%
blue; right: polygonal match. Matched DB ele- ^ alarm, otherwise they are ignored. Finally, remain- Ing a
ments in green. False detected elements in red. ing polygons representing parts of the non-matched part
DB buildings might be considered as viewed if the fied (
that are narrower than a threshold, and if their width have
The false alarms are thus made of non matched de- — is indeed smaller than the original width of the build- The :
tected linear segments and parts of non-matched ing in the DB. ral zZ.
detected polygons. The missed elements are DB tion ı
segments or part of DB segments that were not mat- The last process consists in trying to match the re- the f;
ched with a linear segment and did not fit in a de- maining points and lines with parts of polygonal inter]
tected polygons. DB elements. Secor
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