h b;
À -
À o
incluent RE mm A L
a; contour of a
sod A / d; chart object |
- : "i a;
enu NI IE Lt :
Ti ; Radar echo
Sp; +* A | ; > E
: Si : |
| | 7
Sr; ky.
Figure 3: Geometric properties for matching [
described by a weighting factor h; in equation (7). With:
So each measurement r;, p; is weighted by a matrix Figure 4:
given in the specific (£;,n;)-system by the equation: image
- i SO
2, gi — 202 Sin (a; (Pi Vi)
= A vas | |
Weim: =. hu [E | Am | | A& Am 1] 4128 cos? (o; — p; — y). (9) distance
1 à or is shown.
= hi | 0 d | (7) With vectorial weighting the corrections for the ini- iE de
oF tial position and heading can be computed as: the rhaick
Furthermore the distance vectors contain informa- around th
tion depending on their direction. As described, they À 30
4 Y * ol T T G - CO
are perpendicular to the chart contours and represent ASR = [M WM] M Wd (10) tions. It i
a distance information in this specific direction. As Wi 0 transvers
most of the chart objects are oriented along the water- With. NV. : tudinal dir
way, most distance vectors are oriented transversal to 0 :
the waterway. Thus there is only little information for Wa
matching in the longitudinal direction. The available hesrosultwot>maichntewadar imageanchiéles 4.2 Mat
information can be exploited appropriately, when the tronie* chérteisythe ns en Ast 9c the initial cha
measurements are weighted vectorially. The weight- de : R
ina maux AN. is transforned-inio ihe Cartesian position and heading and the covariance matrix The mat
(a;,b;)-system. This system is oriented along the con- Cn = [M ] as a measure of the accuracy p ides
tour of the chart object. For matching, only the com- O9btained by the matching process. eading «
ponent in the b;-direction is relevant. The weight in To illustrate the matching of radar echos and chart basic req
the a;-direction is set to zero, as there is no informa- ~~ contours two radar images are given in figure 4 and 5. ours isto
tion available. After a further transformation into the The own ship is displayed in the lower middle of the in the ra
global coordinate system, the weighting matrix of a 'Mages as a small ship symbol. The grey areas are With alm
measurement is given by: the radar echos acquired by the computer. The tick stream lik
marks at the frame are 100 m apart. These images level can
were recorded on the river Rhine near Mannheim. Duisburg
Wo | Wn: wi; | The electronic chart is superposed to the radar im- river bani
Via; 22, ages. In figure 4 the distance vectors are also plotted. visible.
5 gi Sin? a; gi sina; cos a; (8) In this figure the initial values of the matching process the river,
= gi Sino; COS o; gi COS? ai have been changed manually to generate significant with rade
68
