Lecture 3: Vector Analysis
What are the basic geometric vector operations?
computation of distance b/w 2 features, calculating the length of line objects, calculating polygon areas, calculating line intersects
Name the four computation of distance
Euclidian distance, distance in a network, topographical distance, spherical distance
What does it mean if the # of intersections is odd in point-in-polygon?
the point is in the polygon
What is the result of a buffer zone?
Polygon layer
Which three vector overlays are there?
points in polygon, lines in polygon, polygons in polygons
Points on Polygons:
Decide which points lie in which polygons, transfer attributes from the polygons to those points that fall within them (one to many) and the result is a point LAYER with their original + polygon attributes
What is not automatically updated in shape file format?
length and area attributes
Common problem with polygon on polygons?
Slivers
What are the post overlay clean-up operations?
clip, dissolve, merge, eliminate
Explain clip
Same principle as polygon on polygon only no attributes from clip layer included in result table
Explain dissolve
It makes new bigger polygons based on attribute values
Eliminate
Used to remove slivers based on a certain threshold value
Merge
bringing together two data layers in order to make a larger database
What influences vector analysis?
map projection, generalisation, precision