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Select by Location "remove from currently selected" versus Erase - different results. Why?

Question asked by am95405 on Jan 26, 2017
Latest reply on Jan 27, 2017 by jayanta.poddar

ArcGIS for Desktop 10.3.1

Source data: ESRI modules regarding Crater Lake (Spatial Analysis)


The objective of the analysis was to remove areas that are within 1 mile of a road, as to find suitable habitat for bald eagles that are under the trees and near water. Let's call the layer file for trees and water "trees" for simplicity.


Method 1 : Trees --> Select All --> Select by Location à Remove from current selection, those within 1 mile of roads (are within a distance of the source layer feature) à Result: a feature layer with 6774 rows, with a total area of ~8,000 acres


Method 2:  Road à Create 1 mile buffer (Call this RoadBuffer). Erase (Trees, Road Buffer) à  Result: a feature layer with 7097 rows, with a total area of ~20,000 acres


When I look at the images (I've attached a snapshot here), Method 2 results make sense. I am not quite sure how Method 1 is working, and Method 1 is actually what the ESRI virtual campus suggests.


How are these two functions implemented differently? The buffer/erase method I can easily understand, but how is select by location, remove ... implemented?