{"id":121711,"date":"2008-03-21T21:05:00","date_gmt":"2008-03-21T21:05:00","guid":{"rendered":"http:\/\/www.esri.com\/arcgis-blog\/products\/product\/uncategorized\/python-script-tool-for-selecting-polygons-for-maps-at-smaller-scales\/"},"modified":"2008-03-21T21:05:00","modified_gmt":"2008-03-21T21:05:00","slug":"python-script-tool-for-selecting-polygons-for-maps-at-smaller-scales","status":"publish","type":"blog","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/product\/mapping\/python-script-tool-for-selecting-polygons-for-maps-at-smaller-scales","title":{"rendered":"Python script tool for selecting polygons for maps at smaller scales"},"author":4351,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"open","ping_status":"closed","template":"","format":"standard","meta":{"_acf_changed":false,"_searchwp_excluded":""},"categories":[22941],"tags":[38211,23211],"industry":[],"product":[],"class_list":["post-121711","blog","type-blog","status-publish","format-standard","hentry","category-mapping","tag-arcgis-methods","tag-map-data"],"acf":{"short_description":"By Charlie Frye, Esri Chief Cartographer\n\n\n\nWhich are the 30 or 500 most important of Minnesota\u2019s famous 10,000 lakes?\u00a0 Next, think ab...","flexible_content":[{"acf_fc_layout":"content","content":"

By Charlie Frye, Esri Chief Cartographer<\/strong><\/p>\n

\"Refresh\/reload<\/p>\n

Which are the 30 or 500 most important of Minnesota\u2019s famous 10,000 lakes?\u00a0 Next, think about that question from the point of view of making a zoom-able map of the U.S. and how many lakes need to be shown as you zoom in.\u00a0 That question boils down to how to decide which polygons to show.\u00a0 Not all polygons are created equally, some are roughly round, some are banana shaped (like ox-bow lakes) some have lots of prongs (like a reservoir formed by U.S. Army Corps of Engineers dam), some are long and twisty like a pretzel.\u00a0<\/p>\n

The USGS\u2019s guidance for selecting polygons from their 1:24,000 scale maps to be included on the 1:100,000 scale maps was based on the width of the smallest axis of a polygon. That worked well back in the days when folks used their eyes and hands to make maps.\u00a0 For the modern cartographer databases, keyboards, and mice effectively blunt the senses and the mapmaking process.<\/p>\n

A little over a year ago I took the essence of that USGS guidance and decided to see how far I could push it. The result is a Python script tool (Minimum Bounding Rectangle Polygon Analyzer<\/a>) that analyzes polygons and a method for selecting polygons based on that analysis.<\/p>\n

The analysis depends on creating the smallest minimum bounding rectangle (MBR) around a polygon and analyzing the rectangle and the polygon\u2019s relation to it. This provides three measures that prove very useful in selecting polygons for smaller scales<\/p>\n