Vegetation disturbance status data from the OPERA Land Surface Disturbance Alert from Harmonized Landsat Sentinel-2 product over California, United States, on September 18, 2023.
View full-size imageThe Observational Products for End-Users from Remote Sensing Analysis (OPERA) Land Surface Disturbance Alert from Harmonized Landsat Sentinel-2 (HLS) product Version 1 maps vegetation disturbance alerts that are derived from data collected by Landsat 8 and Landsat 9 Operational Land Imager (OLI) and Sentinel-2A and Sentinel-2B Multi-Spectral Instrument (MSI). A vegetation disturbance alert is detected at 30 meter (m) spatial resolution when there is an indicated decrease in vegetation cover within an HLS pixel. The Level-3 data product also provides additional information about more general disturbance trends and auxiliary generic disturbance information as determined from the variations of the reflectance through the HLS scenes. HLS data represent the highest temporal frequency data available at medium spatial resolution. The combined observations will provide greater sensitivity to land changes, whether of large magnitude/short duration or small magnitude/long duration.
The OPERA_L3_DIST-ALERT-HLS (or DIST-ALERT) data product is provided in Cloud Optimized GeoTIFF (COG) format, and each layer is distributed as a separate file. There are 19 layers contained within the DIST-ALERT product. The layers for both vegetation and generic disturbance include disturbance status, loss or anomaly, maximum loss anomaly, disturbance confidence layer, date of disturbance, count of observations with loss anomalies, days of ongoing anomalies, and day of last disturbance detection. Additional layers are vegetation cover percent, historical percent vegetation cover, and data mask. See the Product Specification Document (PSD) for a more detailed description of the individual layers provided in the DIST-ALERT product.
| Characteristic | Description |
|---|---|
| Collection | SNWG OPERA Disturbance |
| DOI | 10.5067/SNWG/OPERA_L3_DIST-ALERT-HLS_V1.001 |
| File Size | ~17 MB |
| Temporal Resolution | Multi-Day |
| Temporal Extent | 2022-01-01 to Present |
| Spatial Extent | Global (Non-Antarctic) |
| Coordinate System | Universal Transverse Mercator (UTM) |
| Datum | World Geodetic System (WGS84) |
| File Format | Cloud Optimized GeoTIFF (COG) |
| Geographic Dimensions | 109.8 km x 109.8 km |
| Characteristic | Description |
|---|---|
| Number of Science Dataset (SDS) Layers | 19 |
| Columns/Rows | 3660 x 3660 |
| Pixel Size | 30 m |
| SDS Name | Description | Units | Data Type | Fill Value | No Data Value | Valid Range | Scale Factor |
|---|---|---|---|---|---|---|---|
| VEG-DIST-STATUS¹ | Vegetation disturbance status | Class Flag | 8-bit unsigned integer | N/A | 255 | 0 to 8 | N/A |
| VEG-IND | Current vegetation cover indicator | Percent | 8-bit unsigned integer | N/A | 255 | 0 to 100 | N/A |
| VEG-ANOM | Current vegetation anomaly value | Percent | 8-bit unsigned integer | N/A | 255 | 0 to 100 | N/A |
| VEG-HIST | Historical vegetation cover indicator | Percent | 8-bit unsigned integer | N/A | 255 | 0 to 100; 200=No disturbance | N/A |
| VEG-ANOM-MAX | Max vegetation anomaly value | Percent | 8-bit unsigned integer | N/A | 255 | 0 to 100 | N/A |
| VEG-DIST-CONF | Vegetation Disturbance Confidence Layer | N/A | 16-bit signed integer | N/A | -1 | 0=No disturbance; >0=Disturbance confidence | N/A |
| VEG-DIST-DATE | Date of initial vegetation disturbance | Day | 16-bit signed integer | N/A | -1 | 0=No vegetation anomalies in the last year; >0=Day of initial anomaly detection in the last year | N/A |
| VEG-DIST-COUNT | Number of detected vegetation loss anomalies | N/A | 8-bit unsigned integer | N/A | 255 | 0=No disturbance; 1 to 254=Count of loss anomalies | N/A |
| VEG-DIST-DUR | Vegetation disturbance duration | Day | 16-bit signed integer | N/A | -1 | 0=No disturbance; 1 to 366=Number of days from first anomaly to most recent anomaly detection | N/A |
| VEG-LAST-DATE | Date of last observation assessed for vegetation disturbance | Day | 16-bit signed integer | N/A | -1 | ≥1=Last day assessed | N/A |
| GEN-DIST-STATUS² | Generic disturbance status | Class Flag | 8-bit unsigned integer | N/A | 255 | 0 to 8 | N/A |
| GEN-ANOM | Current generic disturbance anomaly value | N/A | 16-bit signed integer | N/A | -1 | 0=No disturbance; >0= Spectral distance | N/A |
| GEN-ANOM-MAX | Generic disturbance maximum anomaly value | N/A | 16-bit signed integer | N/A | -1 | 0=No disturbance; >0= Spectral distance | N/A |
| GEN-DIST-CONF | Generic Disturbance Confidence Layer | N/A | 16-bit signed integer | N/A | -1 | 0=No disturbance; >0=Disturbance confidence | N/A |
| GEN-DIST-DATE | Date of initial generic disturbance | Day | 16-bit signed integer | N/A | -1 | 0: No spectral anomalies in the last year>0: Day of initial anomaly detection in the last year | N/A |
| GEN-DIST-COUNT | Number of detected spectral anomalies | N/A | 8-bit unsigned integer | N/A | 255 | 0=No disturbance; 1 to 254=Count of loss anomalies | N/A |
| GEN-DIST-DUR | Generic disturbance duration | Day | 16-bit signed integer | N/A | -1 | 0=No disturbance; 1 to 366=Number of days from first anomaly to most recent anomaly detection | N/A |
| GEN-LAST-DATE | Date of last observation assessed for generic disturbance | Day | 16-bit signed integer | N/A | -1 | ≥1=Last day assessed | N/A |
| DATA-MASK | Mask of pixels the algorithms are applied to in the current HLS scene | N/A | 8-bit unsigned integer | N/A | N/A | 0=Not land;1=Land; 2=Water | N/A |
| Value | Description |
|---|---|
| 0 | No disturbance |
| 1 | First <50% |
| 2 | Provisional <50% |
| 3 | Confirmed <50% |
| 4 | First ≥50% |
| 5 | Provisional ≥50% |
| 6 | Confirmed ≥50% |
| 7 | Confirmed <50% finished |
| 8 | Confirmed ≥50% finished |
| 255 | No data |
“Provisional” is used from the first detection until vegetation disturbance/generic spectral differences are detected for a consecutive number of HLS scenes, when it is then labeled “confirmed.” If a “provisional” disturbance does not have repeated detections, it is removed. These labels are reported for both above and below the 50% disturbance threshold.
| Value | Description |
|---|---|
| 0 | No disturbance |
| 1 | First low |
| 2 | Provisional low |
| 3 | Confirmed low |
| 4 | First high |
| 5 | Provisional high |
| 6 | Confirmed high |
| 7 | Confirmed low, finished |
| 8 | Confirmed high, finished |
| 255 | No data |
For more information about raster layers see Table 4-1 in the PSD.
Additional usage constraints are provided under Section 5 of the Algorithm Theoretical Basis Document (ATBD).