PRACTICE 2

Ice age bathtub

goal

Your goal is to import a digital elevation model (DEM) and make a Map with the four layers shown in the app below. When you have finished solving the problem (or when the clock is approaching 5pm on Friday), please work through the check-up on Canvas as best you can.

open app in new tab

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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.  

// -------------------------------------------------------------------------------
//  Gather image from "projects/ee-patterns/assets/p02/NOAA-CoNED-SOCAL".
//  Print a histogram - do you see land vs ocean floor in the histogram?
// -------------------------------------------------------------------------------

var image = ee.Image("projects/ee-patterns/assets/p02/NOAA-CoNED-SOCAL");

print("Image", image);


// -------------------------------------------------------------------------------
//  Area of interest for practice problem.
// -------------------------------------------------------------------------------

var aoi = image.geometry();


// Center map on aoi at zoom level 9 and set base layer to hybrid.




// -------------------------------------------------------------------------------
//  Apply a vertical exageration (z-factor) of 2 to elevation data for hillshade. 
//  Make a hillshade from this image and display the hillshade image as layer on Map.
// -------------------------------------------------------------------------------

var image_ve ;

var image_hs ;


// -------------------------------------------------------------------------------
//  Separate the original elevation image (without vertical exageration) into two different images:

//  (1) land elevations
//  (2) ocean floor elevations (bathymetry)

//  Each image should only store land or bathymetry elevation values, respectively.
//  All other values should be masked.
// -------------------------------------------------------------------------------

var image_land ;

var image_bathy ;

// -------------------------------------------------------------------------------
//  Reclassify the bathymetry image at 100 meter intervals. 
//  Display the reclassified image as layer on Map with 0.5 opacity.
//  To improve contrast, set max of viz dictionary such that all locations less than -2000 m (or class 20) are the darkest blue in palette.
//  Use this palette: geo.iPalettes.iBathy.eleven
// -------------------------------------------------------------------------------



var image_bathy_reclass ;



// -------------------------------------------------------------------------------
//  Define the Pleistocene shoreline as 130 meters lower than today's shoreline.
//  Make a boolean image that shows all land above ocean in Pleistocene.
//  Display boolean image as layer on Map with all non-land masked.
//  Set opacity of layer at 0.5.
// -------------------------------------------------------------------------------

var image_pleistocene ;


// -------------------------------------------------------------------------------
//  Reclassify the land image at equal 100 meter intervals. 
//  Display the reclassified image as layer on Map with 0.5 opacity.
//  Use this palette: geo.iPalettes.iHypso.bartholomew
//  Set opacity of layer at 0.5.
// -------------------------------------------------------------------------------

var image_land_reclass ;




// -------------------------------------------------------------
//  PRACTICE CHECKS
// -------------------------------------------------------------

//  I. QUANTITATIVE 

print("QUANTITATIVE CHECKS:");

//  Import check module for tutorial 1.

var check = require("users/jhowarth/eePatterns:checks/p02.js");

//  Uncomment the five lines below, run script, and look at the results in Console. 

// check.checkPoint("CP1:", image_hs);
// check.checkPoint("CP2:", image_land);
// check.checkPoint("CP3:", image_bathy);
// check.checkPoint("CP4:", image_pleistocene);
// check.checkPoint("CP5:", image_bathy_reclass);

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advice on printing histograms

This is a BIG dataset. Whenever you print histogram or min-max values, set the scale to 30 and the extent to aoi.

print("Image histogram", geo.iCart.iHistogram(image, 30, aoi));

print("Min & max value of image", geo.iCart.iMinMax(image, 30, aoi));

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check definitions

VARIABLE	DESCRIPTION
image_hs	Hillshade image from elevation data with vertical exaggeration of 2, azimuth 315, and zenith 35.
image_land	Land elevations only. All sea floor elevations should be masked.
image_bathy	Sea floor elevations only. All land elevations should be masked. Include 0 elevation as sea floor.
image_pleistocene	Flexible depending on how you solve this. It could represent sea floor elevations when the sea-level was 130 meters lower than today, or you could skip this step and just define the boolean image. Many different answers are potentially fine for this one and we will discuss in class on Monday.
image_bathy_reclass	Modern sea floor (bathy) elevations reclassified into equal interval classes.

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data sources

CoNED

GEE Awesome Community Datasets

CoNED Data Archive

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