7/25/2019 Basic GPS

1/2

Module 2 : Global Positioning Syste m L e c t ur e 1 1 : S a t e l l it e g e om e t r y a n d A c c u r a c y m e a s u r e s

Geometrical interpretation of Dilution of PrecisionDOPAs mention ed earl ier DOP is an ind icator of three dime nsion al posi tioni ng accuracy as conseq uen ce of rela tive positio n of

G P S s a t e l l l i t e s w i t h r e s p e c t t o a G P S r e c e i v e r . I n o r d e r t o a t t a c h a g e o m e t r i c a l i n t e r p r e t a t i o n t o t h i s , w e u s e a t e r m c a l l e dg e o m e t r i a c l d i l u t i o n o f p r e c i s i o n o r G D O P . F i g u r e 1 1 . 2 a n d 1 1 . 3 e x p l a i n a s i m p l e i n t e r p r e t a t i o n f o r t h i s . A c l o s e b u n c h i n g o r p o o r l y s p a c e d s a t e l l i t e s g i v e s p o o r G D O P v a l u e w h e r e a s w e l l d i s t r i b u t e d s a t e l l i t e s y i e l d g o o d G D O P . F o r a n i d e a l s i t u a t i o ni . e o n e s a t e l l i t e o v e r h e a d w i t h t h e o t h e r s s p a c e d a t e q u a l h o r i z o n t a l a n g l e s a b o u t t h e o b s e r v e r , w i l l g i v e t h e b e s t G D O P .

Figure 11.2 Spatial geometry for GDOP values (Dana, 2000)

Figure 11.3 Spatial geometry for GDOP values (Dana, 2000)

I n l i t e r a t u r e , d i f f e r e n t t y p e s o f D O P d e s i g n a t i o n s a r e i s u s e . F o r e x a m p l e , G D O P , P D O P , e t c . T h e s e a r e g i v e b e l o w :G D O P : G e o m e t r i c a l D i l u t i o n o f P r e c i s i o n , ( m e a s u r e o f a c c u r a c y i n 3 - D p o s i t i o n a n d t i m e )P D O P : P o s i t i o n D i l u t i o n o f P r e c i s i o n ( m e a s u r e o f a c c u r a c y i n 3 - D p o s i t i o n ) , a l s o c a l l e d s p h e r i c a l D O PH D O P : H o r i z o n t a l D i l u t i o n o f P r e c i s i o n ( m e a s u r e o f a c c u r a c y i n 2 - D p o s i t i o n , f o r e x a m p l e L a t i t u d e a n d L o n g i t u d e )V D O P : V e r t i c a l D i l u t i o n o f P r e c i s i o n ( m e a s u r e o f a c c u r a c y i n 1 - D p o s i t i o n , H e i g h t )T D O P : T i m e D i l u t i o n o f P r e c i s i o n ( m e a s u r e o f a c c u r a c y i n T i m e )

P D O P i s a l s o i n t e r p r e t e d a s i n v e r s e l y p r o p o r t i o n a l t o t h e v o l u m e , V, o f a t e t r a h e d r o n t h a t i s f o r m e d f r o m t h e s a t e l l i t e a n du s e r p o s i t i o n s ( P D O P 1 /V) . T h e s e D O P v a l u e s a r e r e l a t e d t o p o s i t i o n i n g e r r o r s a n d U E R E b y t h e f o l l o w i n g e x p r e s s i o n s

w h e r e r i s U E R E , H, V , P a n d T a r e s t a n d a r d d e v i a t i o n s i n h o r i z o n t a l , v e r t i c a l , p o s i t i o n ( b o t h h o r i z o n t a l a n d v e r t i c a l ) ,a n d t i m e r e s p e c t i v e l y .

7/25/2019 Basic GPS

2/2

1 2 3 4 5 6 7 8

http://nptel.ac.in/courses/105104100/lectureB_11/B_11_63D.htmhttp://nptel.ac.in/courses/105104100/recap/B_11_Recap.htmhttp://nptel.ac.in/courses/105104100/lectureB_11/B_11_2sat_geo.htmhttp://nptel.ac.in/courses/105104100/lectureB_11/B_11_5calculation.htmhttp://nptel.ac.in/courses/105104100/lectureB_11/B_11_4interpret.htmhttp://nptel.ac.in/courses/105104100/lectureB_11/B_11_4interpret.htmhttp://nptel.ac.in/courses/105104100/lectureB_11/B_11_2sat_geo.htmhttp://nptel.ac.in/courses/105104100/objectives/B_11_Objectives.htmhttp://nptel.ac.in/courses/105104100/lectureB_11/B_11_3GDOP.htmhttp://nptel.ac.in/courses/105104100/lectureB_11/B_11_7absolute.htm