OverviewTeaching: 5 min Exercises: 10 minQuestions
What are the key features of the online code editor?
Where can I go for help while learning GEE?
How do I search for and import datasets?
How do I create, share and save scripts?Objectives
Get oriented to the tools available in the code editor
Load an image collection and filter it to a relevant image
Create a study area using Geometry tools
GEE has an integrated development environment (IDE) called the Code Editor. The Code Editor has number of features to help make programming in this environment easier that we will explore in this tutorial. For an exhaustive description see the Earth Engine Code Editor help page in the GEE User Guides.
Link to the full code we used in this lesson: https://code.earthengine.google.com/926160c96272a205b91b5ed7b68981ab
To access the Code Editor, type the following url into your browser: https://code.earthengine.google.com A webpage programming interface like the one below should appear. The diagram below has annotations pointing to many of the functionalities we will cover today.
For example, you can write comments by using a double slash. Type the following into your Editor and click the “Run” button.
You can also use
print() to display things to the console. Type this and click “Run”:
The Editor will mark statements as incomplete
i if you write them without a semicolon at the end. You can control these autosuggestions by going to the little grey wheel in the top right of the page and turning them on or off.
Save scripts by clicking the Save button. To include a commit message, use the dropdown arrow and select “Save with a description.” Messages are stored in the revision history of each saved script.
Note: If you didn’t make any changes to the script, the Save button will be greyed out.
If you look at the top left panel, you can see the script is now saved in your Scripts manager. You have three categories of scripts: private, shared and examples. Each script is backed up on Git. If you move your mouse over the name of the script, three icons will pop up that allow you to revert to older versions, rename or delete the script. You can also make folders and click and drags scripts into those directories.
Note/Warning: If you rename a script, it’s revision history disappears.
You can share a static version of scripts by clicking Get Link. A url will appear in your browser address field. Share this link to give other people access to your code as it is. If you continue to make edits on this code, they will not update in the linked version. This option is useful to share examples and code snapshots with others.
**Hot Tip: When posted on the help forum, ALWAYS include a link to your code so people can help troubleshoot. Be sure all personal assets you use are publicly shared so the script will run for others.**
To collaborate interactively on shared scripts with other users, you can create a shared folder, invite your collaborators and place scripts in that folder. We have created a shared folder for geohackweek2019.
You should have already accessed the shared code repository in the Code Editor with the following steps:
Accept the shared repository by clicking this link: https://code.earthengine.google.com/?accept_repo=users/victorialy/geohackweek2019
Any updates will be reflected in these versions of the code. Like all GEE scripts, these are version controlled. Read or write permissions for individuals or groups can be set in the Code Editor using the little grey share icon that appears to the right if you move your mouse over the directory name in the Scripts tab. You should have read-only access to this repo.
To query the GEE data catalog, you can enter key words into the search toolbar at the top of the code editor.
For practice, let’s load some imagery into the code editor. We are going to search for and import the Landsat Top of the Atmosphere (TOA) Reflectance Collection 1 Tier 1 product.
ImageCollection IDshould say LANDSAT/LC08/C01/T1_TOA
ImageCollection) will load into your Code Editor in the “Imports” pane at the top of the code editor.
ImageCollection, which means it is a stack of images. Notice we have to declare this object using var. If you click the little blue square icon above the collection, a pop-out will appear showing the code you just created.
In order to look at the collection, try to print it just like you did the string.
Earth Engine times out - this means your request is too big, which makes sense as there are thousands of images in the Landsat 8 collection. To get around this, try the following:
This will show you just the first five images so you can preview the collection. You can see the collection ID, the bands, the features, which are the images in the collection and the properties, which is the metadata.
The geometry drawing tools located on the upper left side of the map viewer can be used to manually create points, line or polygons. We are now going to define a study area using a point we select on the map. We will use the Geometry Tools to create that point.
You have now created a new point object and cast it as a
FeatureCollection. You can now use this
FeatureCollection as a way to geographically filter datasets for just your region.
Having fun? You can further explore how to configure geometries in the Classifying Imagery section of this tutorial.
We are going to filter the collection down to one image by:
Essentially, this allows us to sort through the full Landsat 8 collection and load the best image available for our region of interest for 2018.
Use a print statement to check out what we just made:
We have now filtered the ENTIRE Landsat 8 archive down to the least cloudy image for our study area in 2018. However, we still need to visualize it, which we will do using the
Note: Not sure what this function does? Search for it in the Docs tab to learn the arguments.
That doesn’t look so great. Let’s actually define what bands to use and fill in some other visualization parameters using the layer manager. We will use reflectance in the visible range from the red (Band 4), the green (Band 3) and the blue (Band 2) to make a true color image. We can use prior knowledge to make a nice image:
More often then not, though, you may not know the optimal min, max and stretch. This is why they added the Layer Manager tool which can be found in the upper right hand corner of the map. This toolbar will allow you to click layers on and off as well as adjust their transparency and interactively configure each layer’s visualization parameters. You can use this tool to figure out what parameters to pass to the
You can also toggle between the Map or Satellite buttons in the top right of the map panel to change the baselayer.
Another way you can inspect and explore your image is through the inspector tool. The Inspector console allows you to interactively query the map. If you have imagery loaded, it will give you information about that imagery at the point you clicked as well.
In the upper right, switch to the Inspector tab and click on the map where there is land. Now click where there is water. Toggle the between the graph and the list of values.
On your own, play with the stretch parameters and use the Inspector to explore the map, clicking between land, bare earth, forest and water.
If you already did that, you can play with dropping the point somewhere else and looking at a different image of your favorite place.
You could also change the dates to look at a winter time image and see how the reflectance changes when there is snow on the ground.
There are many entry points for getting help tucked into the Code Editor. Familiarizing yourself with these tools can help soften the learning curve.
The Help button is a gateway to many resources, including links to:
the Developers Guide for official GEE tutorials, reference and guides. This is the first place I go when I need to look up how to write some code.
the Help Forum where you can post questions and get answers. If I can’t find a guide for my specific question on the GEE Guides, I then go search for key words from my problem/question on the forum. Since people share links to their codes, you can often find great examples of solutions here.
A list of keyboard shortcuts
links to the Suggest a Dataset page
A final place you can get help is by scrolling down and looking at the examples housed in the Shared Scripts in the Scripts tab.
Besides using all of Google’s amazing archives, users can also import their own data as either images (rasters) or tables (vectors). The Assets tab on the left is where you can import, share and manage these own assets. You can upload images or tables (vector data) here.
When posting on the forum, make sure you check the “Anyone Can Read” box on the sharing assets pop-out so folks on the forum can all run your code. If you have a private asset and you don’t make it public, other people will not be able to run your code. If you don’t want to share your private data, you can create a dummy example to share on the forums using hand drawn points or polygons.
For an example script that uses imported data, see Episode 06 Time Series. For detailed instructions from Google on uploading, sharing and managing assets, see the Assets Manager page on the GEE website .
Instead of printing to the console, for larger tasks you may want to just export the outputs to your Google Drive or Cloud Storage using the
Export functions in your code. When run, these generate a new task in the
Task tab in the upper right panel. You will need to then “Run” this task in order to actually start the export. Once you start an export task, you will be prompted to enter details about the resolution, size, format and destination if you did not include this in your code. You can hover your mouse over the task and click the “?” icon to see the status and also to get the task number. If your task isn’t executing, you can share this number as a reference on the developers forum.
We will do an example table export in Episode 3: Load Imagery of this tutorial.
For detailed instructions on exports, see the Exporting Data page on the GEE website. We will also have small export examples in subsequent modules of this tutorial.
The Code Editor is a one stop shop for accessing GEE data catalog and conducting geospatial analysis.
You can use the code editor to develop, share and manage scripts.
You can use the code editor to import, export, share and manage your own personal raster and vector datasets
Use the Docs tab, Example scripts and the HELP button to access the User Guides and Help Forum