Deforestation alert analysis#
Warning
To use this module, you must at least register to the NICFI PlanetLab program and link your GEE account to it. More information can be found at Use Norway’s International Climate and Forests Initiative (NICFI) - Planet Lab data.
Set up#
From the SEPAL app dashboard (purple on the left side), search for and click on deforestation alert analysis.
Note
The launching process can take several minutes
The application should launch itself as a map displaying the world. At the bottom-left side you will find 3 special buttons to open useful links:
the link to the documentation of the module
the link to open a new issue in the github repository
the link to the source code of the application
Clicking on them will open the link in a new webpage.
In the bottom right corner of the map. 3 buttons will help the user navigate through the different widgets of the application:
: the widget to select the AOI (Area of interest)
: the widget to select the alerts and filter them
: the widget to select Planet parameters
In the top left corner there is button to open the metatada interface. More information in the next sections of this document.
Parameters#
The settings need to be fully validated to load the alerts on the map. It has 3 sections that need to be filled in order:
AOI
Alert
Planet (optional)
Area of interest#
The Area Of Interest (AOI) is set using the same interface as in other applications. You can read Area of Interest Selection for more information.
In this step the user will be able to select any type of AOI method. When validated, the AOI will be displayed in gold on the map.
Alert#
The user then needs to select the alert system to use. Various drivers are available in the module and the documentation will reflects any changes or addition made by the SEPAL team.
Follow this process:
Select a driver in the dropdown list. The module will show in blue the area covered by the driver. If you don’t see a background color change, your AOI is not covered
Then select a date range. It can be xx days in the past using the “recent” mode or any time in the past using the “historical” mode.
using the slider, you can filter the minimal size of the alerts from 0 to 100 ha. 0 corresponding to no filter at all.
Note
Some Alert drivers are already filtered by dates, the date selector is thus not displayed
GLAD-L#
Warning
The GLAD-L repository is currently under heavy maintenance, no alerts from 2022 are available. Only historical date from 2018 to 2021 can be selected. More information here.
By selecting this alert system, you will use the GLAD alerts based on the Landsatsatellites.
Since the opening of the Landsat archive in 2008, medium spatial resolution data have been available for use in alert-based applications. Since 2013, two Landsat sensors, the Enhanced Thematic Mapper Plus (ETM+) onboard Landsat 7, and the Operational Land Imager (OLI) onboard Landsat 8, have been systematically acquiring global multi-spectral observations at a 30m spatial resolution. The orbits of the two spacecraft are coordinated to enable potential 8-day repeat coverage globally. Given this cadence, the use of Landsat as a near-real time source of land change information is possible. The data displayed and made available here quantify forest disturbance events for the tropics using ETM+ and OLI data as an input. Daily updates are made for areas where quality land observations are acquired. We define forest cover as 5m tall trees with a canopy closure exceeding 30%. An alert is defined as any Landsat pixel that experiences a canopy loss in excess of 50% cover.
More information on these alerts can be found on the GLAD forest alert page.
RADD#
Note
RADD alerts only cover the tropical part of the Americas and Africa. More information can be found in their documenation.
Selecting this alert system, you will use the RADD alerts:
Sentinel-1’s cloud-penetrating radar provides gap-free observations for the tropics consistently every 6 to 12 days. In the densely cloud covered tropics, this represents a major advantage for the rapid detection of small-scale forest disturbances such as subsistence agriculture and selective logging. The RADD (RAdar for Detecting Deforestation) alerts contribute to the World Resources Institute’s Global Forest Watch initiative in providing timely and accurate information to support a wide range of stakeholders in sustainable forest management and law enforcement activities against illegal deforestation. The RADD alerts are implemented in Google Earth Engine. RADD alerts are available openly via Google Earth Engine, the Global Forest Watch platform, SEPAL.io and EarthMap.org.
More information on these alerts can be found on the Wageningen university portal.
NRT#
Danger
This functionality will remain experimental until the SEPAL team removes the “beta” status on the near real time alert creation recipe.
Selecting this alert system, the user will use the near real time alerts provided by the SEPAL recipe on a specific AOI and for specific dates. You only needs to provide access to the alert asset.
Note
The footprint of the alert is only displayed once the asset is selected.
GLAD-S#
Warning
When publishing this documentation (2022-04-26) only the north part of South America is covered by the alert system. Open the following link to see the area in the GEE code editor.
By selecting this alert system, you will use the GLAD alerts based on the Sentinel 2 satellites.
Loss of primary forest is mapped in near-real time at 10m resolution using Sentinel-2 multispectral data. Cloud, shadow, water are detected in each new Sentinel-2 image and a forest loss algorithm is applied to all remaining clear land observations. The algorithm relies on the spectral data in each new image in combination with spectral metrics from a baseline period of the previous two years. Confidence is built through repeated loss observations in the consequent images.
CUSUM#
Note
this will be using the .tif output of cusum.
Once you’ve run the CUSUM module, you’ll obtain a 3 bands .tif file. Ingest this file in Google Earth Engine using the code editor interface. Once the map is available in your assets you can use it in the module. If you don’t find the asset in the list, click on the icon to reload your asset list.
Note
The footprint of the alert is only displayed once the asset is selected.
SINGLE-DATE#
For this alert driver, the AOI parameter is ignored and all the alerts available in the file be loaded.
Any alert system including a vector file of geometries and metadata. If included the label will be infered from the id and the date of the alert need to be set by the user. By default every alert will be using this one so Planet data will not point straight to the correct images.
Note
Vietnamese forest department is using a specific alert system that works well. It generates a geojson file every 10 days. This system have been developped in partnership with JICA and you can check the GEE application here (vietnamese).
RECOVER#
For this alert driver, the AOI parameter is ignored and all the alerts available in the file be loaded.
The user can save it’s work by exporting the already interpreted alerts in .gpkg forma`. By selecting this format, you will be able to recover your previous analysis and continue the interpretation process.
JJ-FAST#
By selecting this alert system, you will use the JJ-FAST alerts based on ALOS PALSAR data.
The JICA-JAXA Forest Early Warning System in the Tropics (JJ-FAST) can detect deforestation sites with size larger than 2 hectares (Ver. 3.0, as of June 2020). Employing the microwave remote sensing technology, detections can be made even under the thick cloud cover which is characteristic for tropical regions especially during the rainy seasons. The system detects deforestation by means of L-band (1.25 MHz) Synthetic Aperture Radar (SAR) data acquired by the PALSAR-2 sensor aboard JAXA’s Advanced Land Observing Satellite 2 (ALOS-2) and provides the positioning information of detected sites to users free of charge via its web service.
With frequent updates for the entire tropical forest belt, approximately every 1.5 months, JJ-FAST aims to function as an effective deterrent against illegal deforestation activities when it is utilized for forest monitoring in the target countries.
Government forest authorities of tropical countries with large forest inventories are expected to be the main users of JJ-FAST. Since the polygons of detected deforestations cannot only be conveniently viewed online, but also downloaded for further GIS analysis, local authorities are able to effectively identify illegal activities by comparing JJ-FAST detections with available national land use maps and/or concession maps.
Validation#
Once everything is set, the user can click on select alerts and the module will start downloading the information from google earth engine. the module will tile the AOI in smaller chunks to avoid GEE limitation, if you use a big area downloading can take up to 15 min. The alerts are displayed as shapes in red on the map and the settings panel will close automatically. If alerts are found in your AOI.
Metadata#
Click on to show the metadata panel. This panel will allow you to validate the alerts identified by the driver using Planet VHR (Very High Resolution) imagery. All information about the current alert will be displayed in this table:
alert ID: the Id of the alert
geometry edition: a button to trigger geometry edition for one single alert
date: the identified date of the deforestation event
surface: the deforested surface in hectares
coordinates: the coordinates of the center of the alert
review: the visual evaluation performed by the user
comments: some extra comments on the alert
The next sections will cover the editable fields of this table.
alert ID#
on the top you will find the list of alerts ordered by size. To acess them the user can either click on the blue arrows or click on the carret to select one in the dropdown menu. Once an alert is selected (represented now in orange on the map), the Planet panel will open itself on the top right corner of the map and the information of the alert will be displayed.
Tip
To jump from one alert to another, the user can also directly click on the map, the information will be loaded automatically.
Geometry edition#
Some drivers perform automatic analysis and sometimes the geometry of the alerts poorly represent what you see on the VHR imagery. Using this module you can redifine the geometry before exporting your results to perfectly fit the deforested area.
Click on edit geometry. It will release the edition interface (1).
Click on to start edition and move the white square to add or remove vertices.
Once done click on save to exit the edition mode
alternatively:
Click on to start the deletion interface
Click on clear all to remove the edited geometry. The geometry will be returned to it’s original state before any edition was done.
Once the edition is completed click again on the button in the metada panel to stop edition: finish edition.
Date#
If the selected driver embeds the dates of the alerts, this field will be prefield with a meaningful date of deforestation event, if not we take the date found in the file title.
Once the deforestation event is identified you might want to update the date value to reflect what you see on the VHR imagery. Click in the field to use the datepicker.
Review#
By default all alerts are set to unset. After interpreting the Planet imagery, change the value of the radio “review” from:
yes: the alert is valid as well as the dateno: the alert is not valid (no deforestation event)unset: no review has been performed
Export#
At the very bottom of the metadata panel 3 exportation button can be found. Each one will export the alerts and their reviews in a specific format.
to kml#
Export the alerts as a .kml file readable with Google Earth. Each alert will use its ID as label. You can export them at the beginning of the review if you want to use Google Earth in the review process.
to gpkg#
Export the alerts as a .gpkg file readable by any GIS software. It will embed the geometry and all the properties associated with each feature/alert (including the original geometry). This file can be used to save progresses and reused as an input of the process.
to csv#
Export the alerts as a .csv file. Each alert properties are kept and the file represents each feature using the coordinates (lattitude/longitude) of the center of each alert.
Planet imagery#
To interprete the validity of the alert, this module is based on the Planet NICFI imagery.
Parameters#
Note
this panel is fully optional. If nothing is set, the module will use Planet NICFI level 1 data (monthly mosaics). If you have a NICFI level 2 access, providing your API key will grant you access to daily imagery.
click on to access the`planet API interface. In this panel you can connect to your Planet Profile using either your credentials or your password.
Select the credential mode between “credentials” and “API key”
Set and validate your credentials
If the icon is green then you are connected.
Click on NICFI to see the details of the substrictions available with your profile. If the level 2 data are accecible you will be granted access to daily imagery for reviewing steps.
Advance parameters#
Once validated you’ll be able to modify the Planet advance parameters. These parameters are used to request images to Planet, some default parameters have been set but changes may improve the readability of the image.
number of images: the max number of images to display on the map, default to 6
day before: number of previous day the interface can search for images. useful when lot of cloud coverage, default to 1
day after: number of previous day the interface can search for images. useful when lot of cloud coverage, default to 1
cloud coverage: the requested maximal cloud coverage of the images, default to 20%
Level 1 (monthly)#
Level 1 data are monthly mosaics. When a alert is clicked, the module will load the closest month from the observation date. the user can then use the Planet navigator to change the displayed image. Click on the to change the color of the images from CIR to RGB. The user can select the monthly mosaic directly from the dropdown menu or use the navigation buttons. (res. ) will move from one mont in the past (res. in the future). The will set back on the closest date from the observation date.
Level 2 (daily)#
Warning
This option is only available for users that have a NICFI level 2 access.
Level 2 data are daily imagery. When an alert is clicked, the module will load the closest day from the observation date and display images using the advanced parameters provided by the user.
Tip
Multiple images are displayed at once so don’t hesitate to play with the layer control to hide and show different scenes.
Thus user can navigate through the images using the buttons in the Planet navigator. Click on (res. ) to move one day in the past (res. one day in the future). Click on (res. fa-solid fa-chevron-right ) to move one month in the past (res. one month in the future). The will set back on the closest date from the observation date.
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