mounts

Krakatau

Indonesia

Latitude	Longitude	Altitude	ID
-6.102	105.423	813 m	262000

Monitoring priority:

info: this page has been modified to visualize Sentinel-5P SO₂ images. The old page is still accessible here: link.

display information on page content

Images are sorted by acquisition time, with the most recent acquisition on top:

Sentinel-1 images:

- amplitude: back-scattered radar amplitude (VV polarization); date refers to acquisition time (UTC). The images are speckle-filtered using a neural network, but can be displayed without the filter using the dedicated button "speckle filter on/off".

- interferogram: phase difference between 2 consecutive acquisitions; "dt" = time difference between master/slave images.

- coherence: interferometric coherence. It is a measure of the interferometric quality, as it is related to the level of noise affecting the phase difference between the two SAR images. It ranges between 0 and 1, and reflects the degree of surface change, where values towards 0 (black) indicate a loss of coherence. The main contributions to decorrelation are phase noise due to (i) the temporal change of the scatterers (e.g., vegetation, water, sand-covered areas will appear highly incoherent as the scatterers change continuously), (ii) geometric decorrelation (i.e., images have slightly different look-angles), and (iii) variation in atmospheric water vapor content. Although decorrelation usually renders interferograms useless for measuring ground deformation, it can be used to detect changes in the ground properties (e.g., emplacement of lava flows and eruptive deposits, delineation of eruptive fissures, etc.).

Sentinel-2 images:

- infrared: combination of shortwave infrared bands B12-B11-B8A; the date refers to the acquisition time (UTC), the time difference displayed is calculated with respect to the nearest Sentinel-1 acquisition (+/- n days). A Sentinel-2 image is "paired" with a Sentinel-1 image (i.e., displayed on the same row) if the acquisition time difference is <2 days. Use toggle button to hide/show unpaired Sentinel-2 images.

Sentinel-5P images:

- SO₂: gas densities in the Planet Boundary Layer (PBL) expressed in Dobson Unit (DU), in a 500×500 km box centered around the volcano. The detected pixels contaminated with volcanic SO₂ are overlaid with a semi-transparent gray mask. SO₂ images are displayed on the same line as a Sentinel-1/2 image if the acquisition time difference is <1 day; the time difference displayed is calculated with respect to the nearest Sentinel-1 acquisition (+/- n days). Use toggle button to hide/show "unpaired" Sentinel-5P images.

Select images to display:

Sentinel-1

Amplitude (SAR)

Sentinel-1

Interferogram (InSAR)

Sentinel-1

Coherence (InSAR)

Sentinel-2

Infrared (SWIR)

show all

Sentinel-5P

SO₂ (PBL)

show all

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2025-05-04 11:23 (dt=12 days)

2025-05-05 03:01 (+0.7 days)

2025-05-04 05:46 (-0.2 days)

2025-05-03 02:55

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- time range:		to
- speckle filter (SAR):	on off
- zoom:	on off