OBSERVAÇÃO do WRI: o WRI decidiu parar de atualizar os alertas do FORMA. O objetivo era simplificar a experiência do usuário do Global Forest Watch e reduzir a redundância.
Descobrimos que Terra-i e GLAD eram usados com mais frequência.
Além disso, usando o GLAD como padrão, descobrimos que o Terra-i teve uma performance melhor que o FORMA no mundo todo.
Os alertas do FORMA são detectados usando uma combinação de dois produtos do MODIS: NDVI (Índice de Vegetação por Diferença Normalizada) e FIRMS (Sistema de Informações sobre Incêndios para Gerenciamento de Recursos). As atualizações do NDVI são processadas a cada 16 dias, enquanto as de incêndios são processadas diariamente. Os modelos são desenvolvidos individualmente para cada ecogrupo, relacionando as duas entradas à área de desmatamento e usando os dados anuais de perda de cobertura florestal de Hansen para treinar o modelo. O limite mínimo para se qualificar como um alerta é de 25% do pixel limpo, mas os limites variam de acordo com o ecogrupo para minimizar falsos positivos.
Confira um exemplo de script
para uma introdução rápida aos conjuntos de dados da FORMA.
As imagens nesta ImageCollection contêm as "estatísticas t retificadas invertidas" usadas no cálculo do NTT, o índice de cor da vegetação derivado do NDVI do MODIS que a FORMA usa para medir o escurecimento. Usar um redutor de soma em vários períodos nessa ImageCollection produz uma imagem "NTT".
As imagens são divididas por "ecogroup".
Bandas
Tamanho do pixel 250 metros
Bandas
Nome
Mín.
Máx.
Tamanho do pixel
Descrição
tstat_r
0*
25.41*
metros
Retificada invertida, ou seja, (max(0,-t_stat)), estatísticas t.
* valor mínimo ou máximo estimado
Propriedades de imagens
Propriedades da imagem
Nome
Tipo
Descrição
ano
INT
Ano dos dados mais recentes incluídos no conjunto de dados
quinzenal
INT
O período quinzenal (a cada 16 dias) do ano
ecogroup_id
STRING
ID do ecogrupo associado
Termos de Uso
Termos de Uso
Os conjuntos de dados da FORMA estão disponíveis sem restrições de uso ou distribuição. O WRI pede que o usuário faça a atribuição adequada e identifique o WRI e o GFW, quando aplicável, como a fonte dos dados.
OBSERVAÇÃO do WRI: o WRI decidiu parar de atualizar os alertas do FORMA. O objetivo era simplificar a experiência do usuário do Global Forest Watch e reduzir a redundância. Descobrimos que o Terra-i e o GLAD eram usados com mais frequência. Além disso, usando o GLAD como padrão, descobrimos que o Terra-i teve uma performance melhor que o FORMA no mundo todo. Os alertas do FORMA são detectados …
[null,null,[],[[["\u003cp\u003eThe FORMA dataset provides MODIS-based vegetation change alerts, specifically "reversed rectified t-statistics" used to measure browning, with a resolution of 250 meters.\u003c/p\u003e\n"],["\u003cp\u003eWRI has discontinued updating FORMA alerts, recommending Terra-i and GLAD as preferred alternatives due to their performance and user experience.\u003c/p\u003e\n"],["\u003cp\u003eFORMA alerts were generated using NDVI and FIRMS data, trained with Hansen tree cover loss data, and triggered when 25% or more of a pixel was cleared.\u003c/p\u003e\n"],["\u003cp\u003eThe dataset is organized by ecogroups and includes bi-weekly periods for the years 2012 to 2019.\u003c/p\u003e\n"],["\u003cp\u003eThe FORMA datasets are available for use without restriction, but attribution to WRI and GFW is requested.\u003c/p\u003e\n"]]],["The WRI/GFW/FORMA vegetation t-statistics dataset, provided by the World Resources Institute/Global Forest Watch, spans from 2012 to 2019. It uses MODIS-derived NDVI and FIRMS data to detect forest clearing alerts, updating NDVI every 16 days and fire data daily. Alerts are generated when at least 25% of a pixel is cleared. The dataset, which is no longer updated, provides reversed rectified t-statistics used to measure vegetation browning and is broken down by ecogroup with 250-meter pixel size.\n"],null,["# FORMA Vegetation T-Statistics\n\nDataset Availability\n: 2012-01-01T00:00:00Z--2019-04-23T00:00:00Z\n\nDataset Provider\n:\n\n\n [World Resources Institute / Global Forest Watch](https://www.globalforestwatch.org/)\n\nTags\n:\n[daily](/earth-engine/datasets/tags/daily) [deforestation](/earth-engine/datasets/tags/deforestation) [forest](/earth-engine/datasets/tags/forest) [forest-biomass](/earth-engine/datasets/tags/forest-biomass) [forma](/earth-engine/datasets/tags/forma) [gfw](/earth-engine/datasets/tags/gfw) [modis](/earth-engine/datasets/tags/modis) [monitoring](/earth-engine/datasets/tags/monitoring) [wri](/earth-engine/datasets/tags/wri) \n\n#### Description\n\n**NOTE from WRI** : WRI decided to stop updating FORMA alerts. The goal was\nto simplify the [Global Forest Watch](https://www.globalforestwatch.org)\nuser experience and reduce redundancy.\nWe found that [Terra-i](http://www.terra-i.org/terra-i.html) and\n[GLAD](https://glad-forest-alert.appspot.com/) were more frequently used.\nMoreover, using GLAD as a standard, found that Terra-i outperformed\nFORMA globally.\n\nFORMA alerts are detected using a combination of two MODIS\nproducts: NDVI (Normalized Difference Vegetation Index) and FIRMS\n(Fires Information for Resource Management System). NDVI updates are\nprocessed every 16 days, while fire updates are processed daily. Models\nare developed individually for each ecogroup to relate the two inputs to\nthe area of clearing, using the Hansen annual tree cover loss data to train\nthe model. The minimum threshold to qualify as an alert is 25% of the pixel\ncleared, though thresholds vary by ecogroup to minimize false positives.\nHere is an [example script](https://code.earthengine.google.com/f29b1e4360f3fc36847bd789ceeb20f6)\nfor a quick introduction to the FORMA datasets.\n\nThe images in this ImageCollection contain the \"reversed rectified\nt-statistics\" used in calculating NTT, the vegetation color index derived\nfrom MODIS NDVI that FORMA uses to measure browning. Using a sum reducer on\nover various date ranges in this ImageCollection produces an \"NTT\" image.\n\nThe images are broken by \"ecogroup\".\n\n### Bands\n\n\n**Pixel Size**\n\n250 meters\n\n**Bands**\n\n| Name | Min | Max | Pixel Size | Description |\n|-----------|-----|---------|------------|--------------------------------------------------------|\n| `tstat_r` | 0\\* | 25.41\\* | meters | Reversed rectified, ie (max(0,-t_stat)), t-statistics. |\n\n\\* estimated min or max value\n\n### Image Properties\n\n**Image Properties**\n\n| Name | Type | Description |\n|-------------|--------|------------------------------------------------------|\n| year | INT | Year of the most recent data included in the dataset |\n| biweekly | INT | The biweekly (every 16 days) period of the year |\n| ecogroup_id | STRING | ID of associated ecogroup |\n\n### Terms of Use\n\n**Terms of Use**\n\nThe FORMA datasets are available without restriction\non use or distribution. WRI does request that the\nuser give proper attribution and identify WRI and GFW, where applicable,\nas the source of the data.\n\n### Explore with Earth Engine\n\n| **Important:** Earth Engine is a platform for petabyte-scale scientific analysis and visualization of geospatial datasets, both for public benefit and for business and government users. Earth Engine is free to use for research, education, and nonprofit use. To get started, please [register for Earth Engine access.](https://console.cloud.google.com/earth-engine)\n\n### Code Editor (JavaScript)\n\n```javascript\nvar dataset = ee.ImageCollection('WRI/GFW/FORMA/vegetation_tstats')\n .filter(ee.Filter.date('2018-07-01', '2018-07-15'));\nvar tstat = dataset.select('tstat_r');\nvar visParams = {\n min: 0,\n max: 1,\n};\nMap.setCenter(26, -8, 3);\nMap.addLayer(tstat, visParams, 'Reversed rectified t-statistics');\n```\n[Open in Code Editor](https://code.earthengine.google.com/?scriptPath=Examples:Datasets/WRI/WRI_GFW_FORMA_vegetation_tstats) \n[FORMA Vegetation T-Statistics](/earth-engine/datasets/catalog/WRI_GFW_FORMA_vegetation_tstats) \nNOTE from WRI: WRI decided to stop updating FORMA alerts. The goal was to simplify the Global Forest Watch user experience and reduce redundancy. We found that Terra-i and GLAD were more frequently used. Moreover, using GLAD as a standard, found that Terra-i outperformed FORMA globally. FORMA alerts are detected ... \nWRI/GFW/FORMA/vegetation_tstats, daily,deforestation,forest,forest-biomass,forma,gfw,modis,monitoring,wri \n2012-01-01T00:00:00Z/2019-04-23T00:00:00Z \n-50 -120 40 180 \nGoogle Earth Engine \nhttps://developers.google.com/earth-engine/datasets\n\n- [](https://doi.org/https://www.globalforestwatch.org/)\n- [](https://doi.org/https://developers.google.com/earth-engine/datasets/catalog/WRI_GFW_FORMA_vegetation_tstats)"]]
