Changes between Version 156 and Version 157 of WKTRaster/SpecificationWorking03

Timestamp:

Sep 22, 2011, 8:18:10 AM (13 years ago)

Author:

Bborie Park

Comment:

ST_Intersects

WKTRaster/SpecificationWorking03

@@ -24 +24 @@
  
 
-'''ST_Intersects(raster, raster)'''[[BR]]
-
-This function uses the same tests as the two geometry version of ST_Intersects where tests see if two rasters overlap, touches or has one within the other.  If any condition is true, the two rasters intersect.
-
-For this description, the rasters are called A and B and the bands tested are assumed to be 1.
-
-Preliminary criteria before the real work begins:
-
-1. make sure that rasters A and B have the same SRID.  if not, return false.
-
-2. make sure that the convex hulls of A and B intersect.  if not, return false.
-
-Special case where a raster may be fully contained within another raster's cell (the entirety of A within a cell of B):
-
-1. using every third pixel by row and column, test each selected cell's geopoint (excluding no data by default unless exclude_nodata_value = FALSE) of A to that of B for overlap.
-
-2. if a cell of A does overlap a cell of B, return true.
-
-3. if no cell of A overlaps with B, continue to additional testing
-
-Actual testing involves the use of calculating the intersection of grid lines between A and B
-
-1. Using every third A's column and B's row, calculate the intersection point of each pair of grid lines.
-
-2. If intersection point doesn't exist or is outside the bounds of the end points comprising each grid line used, go back to step 1.
-
-3. If intersection point exists and within bounds, sample the area around the intersection point by offset the intersection point by a small amount (1/10th of the smaller scale of A and B) for 360 degrees starting from 00:00.  sampled points are 0, 45, 90, 135, 180, 225, 270 and 315 degrees.
-
-4. At each sample point, test to see if the geopoint has non-nodata (unless including nodata) values in both A and B.  if so, return true.
-
-5. At the same time as step 4, build an adjacency matrix for the intersection to see if two non-overlapping pixels from A and B touch.
-
-6. Once all sample points have been tested and no overlapping pixels found, the adjacency matrix is checked to see if any sampled pixel of A touched a sampled pixel of B.  If two pixels touched, return true.
-
-7. If after all the searching and testing, nothing intersects or touches, return false.
-
-A set of ST_Intersects functions for rasters:
-
-1. ST_Intersects(raster rastA, raster rastB, integer bandA DEFAULT NULL, integer bandB DEFAULT NULL) -> boolean 
-
-If bandA and bandB are NULL, only the convex hulls of the rasters will be tested.  If bandA or bandB are provided, both parameters must be provided and not NULL.
-
-2. ST_Intersects(raster rastA, integer bandA, raster rastB, integer bandB) -> boolean
-
-A refactored set of St_Intersects() for testing a raster and a geometry.  The first set converts the geometry to a raster to see if the two rasters intersect.
-
-3. ST_Intersects(rast raster, geom geometry, nband integer DEFAULT NULL) -> boolean
-
-4. ST_Intersects(rast raster, nband integer, geom geometry) -> boolean
-
-The second set of ST_Intersects() for testing a raster and a geometry converts the raster to a geometry and sees if the geometries intersect.
-
-5. ST_Intersects(geom geometry, rast raster, nband DEFAULT NULL) -> boolean
-
-The order in which the geometry and raster are passed into ST_Intersects determines which method of testing is used.  If geometry is first, the raster is converted to a set of geometries.  If raster is first, the geometry is converted to a raster.
-
-These set of functions are required because there are cases where ST_Intersects(raster, geometry) != ST_Intersects(geometry, raster).
-
-[[Image(st_intersects_triangle.png)]]
-
-In the image above, the black border denotes the boundary of a triangle polygon and the red within is the raster version of the geometry.  The polygon touches the raster in blue while the red raster does not.
+'''ST_Intersects(raster, raster) -> boolean - done see below'''[[BR]]
 
 '''ST_AsRaster(geometry, pixeltype, val, nodataval, ulx, uly, width, height, pixelsizex, pixelsizey, skewx, skewy) -> raster - done see below'''
@@ -1244 +1184 @@
 == '''Objective FV.02 - Being able to intersect vector and raster to produce raster.''' ==
 
+'''ST_Intersects(raster, raster) -> boolean'''[[BR]]
+
+This function uses the same tests as the two geometry version of ST_Intersects where tests see if two rasters overlap, touches or has one within the other.  If any condition is true, the two rasters intersect.
+
+For this description, the rasters are called A and B and the bands tested are assumed to be 1.
+
+Preliminary criteria before the real work begins:
+
+1. make sure that rasters A and B have the same SRID.  if not, return false.
+
+2. make sure that the convex hulls of A and B intersect.  if not, return false.
+
+Special case where a raster may be fully contained within another raster's cell (the entirety of A within a cell of B):
+
+1. using every third pixel by row and column, test each selected cell's geopoint (excluding no data by default unless exclude_nodata_value = FALSE) of A to that of B for overlap.
+
+2. if a cell of A does overlap a cell of B, return true.
+
+3. if no cell of A overlaps with B, continue to additional testing
+
+Actual testing involves the use of calculating the intersection of grid lines between A and B
+
+1. Using every third A's column and B's row, calculate the intersection point of each pair of grid lines.
+
+2. If intersection point doesn't exist or is outside the bounds of the end points comprising each grid line used, go back to step 1.
+
+3. If intersection point exists and within bounds, sample the area around the intersection point by offset the intersection point by a small amount (1/10th of the smaller scale of A and B) for 360 degrees starting from 00:00.  sampled points are 0, 45, 90, 135, 180, 225, 270 and 315 degrees.
+
+4. At each sample point, test to see if the geopoint has non-nodata (unless including nodata) values in both A and B.  if so, return true.
+
+5. At the same time as step 4, build an adjacency matrix for the intersection to see if two non-overlapping pixels from A and B touch.
+
+6. Once all sample points have been tested and no overlapping pixels found, the adjacency matrix is checked to see if any sampled pixel of A touched a sampled pixel of B.  If two pixels touched, return true.
+
+7. If after all the searching and testing, nothing intersects or touches, return false.
+
+A set of ST_Intersects functions for rasters:
+
+1. ST_Intersects(raster rastA, raster rastB, integer bandA DEFAULT NULL, integer bandB DEFAULT NULL) -> boolean 
+
+If bandA and bandB are NULL, only the convex hulls of the rasters will be tested.  If bandA or bandB are provided, both parameters must be provided and not NULL.
+
+2. ST_Intersects(raster rastA, integer bandA, raster rastB, integer bandB) -> boolean
+
+A refactored set of St_Intersects() for testing a raster and a geometry.  The first set converts the geometry to a raster to see if the two rasters intersect.
+
+3. ST_Intersects(rast raster, geom geometry, nband integer DEFAULT NULL) -> boolean
+
+4. ST_Intersects(rast raster, nband integer, geom geometry) -> boolean
+
+The second set of ST_Intersects() for testing a raster and a geometry converts the raster to a geometry and sees if the geometries intersect.
+
+5. ST_Intersects(geom geometry, rast raster, nband DEFAULT NULL) -> boolean
+
+The order in which the geometry and raster are passed into ST_Intersects determines which method of testing is used.  If geometry is first, the raster is converted to a set of geometries.  If raster is first, the geometry is converted to a raster.
+
+These set of functions are required because there are cases where ST_Intersects(raster, geometry) != ST_Intersects(geometry, raster).
+
+[[Image(st_intersects_triangle.png)]]
+
+In the image above, the black border denotes the boundary of a triangle polygon and the red within is the raster version of the geometry.  The polygon touches the raster in blue while the red raster does not.
+
 '''ST_AsRaster(geometry, pixeltype, val, nodataval, ulx, uly, width, height, pixelsizex, pixelsizey, skewx, skewy) -> raster'''