topic Re: Selecting specific polygons from criteria in Spatial Data Science Questions

Selecting specific polygons from criteria

MalcolmLittle — Sat, 21 Jan 2017 21:38:23 GMT

I have two distinct polygon datasets (both projected the same: NAD 1983 Albers) of lakes and islands in British Columbia. I need a tool/module that’ll select all the lakes that contain an island. Then I need to select from that result the lakes that have surface areas larger than 20 hectares. Working with ModelBuilder, so referring to a model diagram would be appreciated but not necessary.

Re: Selecting specific polygons from criteria

AbdullahAnter — Sat, 21 Jan 2017 21:44:31 GMT

Just you need to use 2 tool :

1- Select Layer By Location to find the lakes that contain an island. Select Layer By Location—Help | ArcGIS Desktop

2-then Use Select Layer By Attribute to select areas larger than 20 hectares. don't forget to make selection method/type in this step " Select from Currant Selection / Subset selection". Select Layer By Attribute—Help | ArcGIS Desktop

Re: Selecting specific polygons from criteria

DanPatterson_Retired — Sat, 21 Jan 2017 22:25:02 GMT

One problem you may run into is if the islands are a bit of a multipart polygon... that is, they are not separate records in the table, but geometrically may be ajoined to the nearby landmap. You might be advised to select by attributes features whose area is less than some probable island-sized value (make sure you are using projected data). Once those values are selected, use the lakes to select from those features that are completely within the lakes. Of course... this assumes that the lakes form a separate layer... if not then things get a bit more complicated.

Re: Selecting specific polygons from criteria

JoshuaBixby — Mon, 23 Jan 2017 15:34:37 GMT

With the lakes dataset, are islands represented by holes in the lake polygon, or are lakes whole and then you have to overlay islands on top of water? I ask because how exactly the data is structured drives the methodology, as others have indicated with their comments.