Select By Location v. Topological Operators


 


RECALL: ATTRIBUTE QUERY OPERATORS – AND, OR

GIS Data Layer:

  • LayerName: PlayingCards
  • Description: There are 52 polygons; each polygon has one record in the attribute table
  • Fields in the attribute table:
    • SUITE: club, spade, heart, diamond
    • COLOR: red, black
    • FACECARD: yes, no
    • VALUE: 1 – 13 (ace = 1, J = 11, Q = 12, K = 13)

Pictures of the 52 playing cards

SAMPLE QUERIES:

‘VALUE’ = 7

‘SUITE’ = “heart” 

‘VALUE’ = 7 OR ‘SUITE’ = “heart” 

‘VALUE’ = 7 AND ‘SUITE’ = “heart” 

 


SELECT BY LOCATION

Now, instead of selecting by an attribute value, an Attribute Query, lets select cards based on a dice roll – specifically, where it lands.

          

Consider the figure above where the die landed on the five-of-spades.  Common questions addressed by SELECT BY LOCATION are:

  • what card(s) did the dice land on (intersect)
  • what card(s) are near the dice (within a distance)

Select by location (relationship = intersect)

The die intersects (passes over or lies across) the five-of-spades.

Select by location (relationship = within a distance)

The 4, 5, an 6 of hearts, diamonds, and spades are all within a (1 card) distance of the dice.

What if we had many dice? 

 

What if we had a landscape instead of cards and dice?

  • What land cover types intersect the river?
  • Which nests are within 500 meters of a river?
  • Which nests are within 500 meters of a river and inside a hardwood stand?

NOTE:  The Select by Location command selects WHOLE polygons and addresses questions like “How many acres of each polygon have at least a part of its shape that falls within our analysis extent?”  It does NOT answer questions like “How many acres are within a 50′ buffer of the river?”

 

ESRI select by location examples…

 

Print Friendly, PDF & Email