Changes between Version 2 and Version 3 of BluePrintGIStools

Timestamp:

01/26/11 05:38:35 (15 years ago)

Author:

Nico Presto

Comment:

expanded number of calcs with examples

BluePrintGIStools

@@ -1 @@
-This list should identify the basic GIS calculations that would be useful in Sahana eden:
+Basic GIS calculations that may be useful in Sahana eden:
+
+* Centroid
+select name, asText(Centroid(the_geom)) from table where name='location';
+
+* Bounding boxes
+select name, asText(Envelope(the_geom) from table where name='location';
+select name, extent(the_geom) from table where name = 'location' group by name;
 
 * buffer calculations
-* intersections (point, line, polygon)
+
+* Distance measurements
+select distance(
+(transform(GeomFromText('Point(lon lat)'), 900913), 26915), 
+(transform(GeomFromText('Point(lon lat)'), 900913), 26915);
+
+* intersections
+select name from location where
+GeomFromText('Point(lon lat)',900913)
+&& the_geom AND
+within (GeomFromText('Point(lon lat)', 900913), the_geom);
+
+* Point within polygon
+select name from location where
+GeomFromText('Point(lon lat)', 900913)
+&& the_geom;
+
+* Spherical distance
+select distance_sphere(
+(transform(GeomFromText('Point(lon lat)'), 900913), 
+(transform(GeomFromText('Point(lon lat)'), 900913);
+
+* Spheroid distance
+select distance_spheroid(
+(GeomFromText('Point(lon lat)'), 900913), 
+(GeomFromText('Point(lon lat)'), 900913),
+'SPHEROID["GRS 1980", 6378137, 298.257222101]');
+