TUTORIAL 3

Introduction to feature collections

goal

This tutorial aims to introduce you to gathering, filtering, and displaying large vector datasets in Earth Engine. Your goal is to work through the starter script and try to reproduce the layers that are shown in the app below.

---

open app in new tab

---

starter script

var geo = require("users/jhowarth/eePatterns:modules/geo.js");

print("geo methods dictionary", geo.help);    // Prints dictionary of all tools in module.  
print("geo palettes", geo.iPalettes);         // Prints dictionary of all palettes in module. 

// ---------------------------------------------------------------------------
//  I. A SIMPLE FEATURE COLLECTION PATTERN
//
//  (1) Gather feature collection from "TIGER/2018/Counties".
//  (2) Note the number of rows in the table, the column names, and the first row of data.
//  (3) Also find all the unique county names in the county. How many are there?
//  (4) Display all the rows in the collection as a Map layer. Use {color: 'white'} 
// ---------------------------------------------------------------------------




// ---------------------------------------------------------------------------
//  II. FILTER BY ATTRIBUTE
//
//  (1) How may counties in the USA are named "Addison"?
//  (2) Display all counties named Addison in the USA on the Map with {color: 'gray'}.
// ---------------------------------------------------------------------------



// ---------------------------------------------------------------------------
//  III. FILTER BY LOCATION
//
//  (1) Use the geometry tool (upper left of Map) to create a point somewhere inside Addison County, Vermont.
//  (2) Filter the original feature collection by location using this poi. 
//  (3) Display the result (Addison county filtered by poi) on the Map with {color: 'black'}.
// ---------------------------------------------------------------------------




// ---------------------------------------------------------------------------
//  IV. FILTER BY MULTIPLE ATTRIBUTES.
//  
//  (1) Filter the original collection for "Orange" county.
//  (2) How many Orange counties are in the USA?
//  (3) Display the result (All counties named 'Orange') on map as layer with {color: 'orange'}.

//  (4) Use AND filter to filter the original collection of counties for "Orange" county IN VERMONT.
//  HINT: the STATEFP column stores strings (even through they look like numbers).
//  (5) Display the result as a layer on the Map with {color: 'OrangeRed'}.
// ---------------------------------------------------------------------------




// ---------------------------------------------------------------------------
//  V. FILTER BY ATTRIBUTE AND LOCATION
//
//  (1) Construct a new feature collection from "TIGER/2018/States".
//  (2) Filter collection for Vermont.
//  (3) Center Map on Vermont. 
//  (4) Add Vermont layer to Map with {color: 'green'}
//  (5) Filter original county collection by name "Orange" and use a FILTER BY LOCATION to filter in bounds of Vermont state.
//  (6) Display result on map with {color: "LightGreen"}
// ---------------------------------------------------------------------------




// ---------------------------------------------------------------------------
//  VI. FILTER BY ATTRIBUTE AND LOCATION: TRICKY CASE
//  
//  (1) Try to reproduce last workflow (FILTER BY ATTRIBUTE AND FILTER BY LOCATION) to map "Essex" county in Vermont.
//  (2) How did it work? What do you think happened?
//  (3) Can you fix it with a workflow that does not use AND but still links together
//    (A) a FILTER BY ATTRIBUTE with 
//    (B) a SPATIAL FILTER  
//  (4) Display the fixed result as a layer to the map with {color: 'magenta'}.
// ---------------------------------------------------------------------------



// ---------------------------------------------------------------------------
//  VII. FIRST CHALLENGE 
//
//  (1) How could you select all the counties in Vermont using a FILTER BY ATTRIBUTE workflow?
//  (2) After you filter the data, add the result  {color: "PowderBlue"}
// ---------------------------------------------------------------------------



// ---------------------------------------------------------------------------
//  VIII. SECOND CHALLENGE
//
//  (1) How could you select all the counties in Vermont using a FILTER BY LOCATION workflow?
//  (2) After you filter the data, add the result  {color: "DeepSkyBlue"}
// ---------------------------------------------------------------------------



// ---------------------------------------------------------------------------
//  IX. FINAL TASK
//  
//  (1) Convert one of the counties in Vermont dataset (VII or VIII) to nominal image 
//  (2) Display each county in a unique color.
// ---------------------------------------------------------------------------

checks in starter

Here are some checks that you can print to Console for sections I - V.

SECTION	DESCRIPTION	CHECKS
I-2	Number of rows in table.	3233
I-2	Column names	18 of them, beginning with GEOID and ending with METDIVFP
I-2	First row of table	id: 00000000000000000011; geometry: Polygon, 656 vertices; properties: 17
I-3	Unique county names	1922 of them
II-1	Number of rows in table	1
III-2	Number of rows in table	1
IV-2	Number of rows in table	8
V	Number of rows in table (states)	56

For sections VI - IX, you should be able to check your work by visually comparing your map layers to the ones shown in the app above.

---

This work is licensed under CC BY-NC-SA 4.0