[postgis-tickets] [PostGIS] #2577: ST_Project() doc update

[PostGIS]

#2577: ST_Project() doc update
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 Reporter:  pcreso                    |       Owner:  robe         
     Type:  defect                    |      Status:  new          
 Priority:  low                       |   Milestone:  PostGIS 2.1.2
Component:  documentation             |     Version:  2.0.x        
 Keywords:  ST_Project documentation  |  
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 As per a list discussion with Paul Ramsey, some clarification in the
 ST_Project() function docs.

 The current docs describe an int azimuth as input to determine the
 direction to propagate a line to fit the output point to. In fact it is
 the starting direction of a great-circle arc with varying bearing.

 Current text:

 Name

 ST_Project — Returns a POINT projected from a start point using a distance
 in meters and bearing (azimuth) in radians.
 Synopsis

 geography ST_Project(geography g1, float distance, float azimuth);
 Description

 Returns a POINT projected from a start point using an azimuth (bearing)
 measured in radians and distance measured in meters.

 Distance, azimuth and projection are all aspects of the same operation,
 describing (or in the case of projection, constructing) the relationship
 between two points on the world.

 The azimuth is sometimes called the heading or the bearing in navigation.
 It is measured relative to true north (azimuth zero). East is azimuth 90
 (pi/2), south is azimuth 180 (pi), west is azimuth 270 (pi*1.5).

 The distance is given in meters.


 Proposed text

 ''Name

 ''ST_Project — Returns a POINT projected from a start point on a great
 circle arc using a distance in meters and initial bearing (azimuth) in
 radians.

 ''Synopsis

 ''geography ST_Project(geography g1, float distance, float azimuth);

 ''Description

 ''Returns a POINT projected along a great circle from a start point using
 an azimuth (bearing) of the start of the arc measured in radians and
 distance measured in meters.

 ''Distance, azimuth and projection are all aspects of the same operation,
 describing (or in the case of projection, constructing) the relationship
 between two points on the world.

 ''The azimuth is sometimes called the heading or the bearing in
 navigation. It is measured relative to true north (azimuth zero). East is
 azimuth 90 (pi/2), south is azimuth 180 (pi), west is azimuth 270
 (pi*1.5). This specifies the start azimuth, the actual direction of the
 line varies along the arc of the great circle line.

 ''The distance is given in meters.

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/2577>
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