WRI 的注意事项：WRI 决定停止更新 FORMA 提醒。目标是简化 Global Forest Watch 用户体验并减少冗余。
我们发现，Terra-i 和 GLAD 的使用频率更高。
此外，使用 GLAD 作为标准，发现 Terra-i 在全球范围内优于 FORMA。
FORMA 警报是通过结合使用两种 MODIS 产品来检测的：NDVI（归一化差值植生指数）和 FIRMS（资源管理系统火灾信息）。NDVI 更新每 16 天处理一次，而火灾更新每天处理一次。针对每个生态群组单独开发模型，以将这两个输入与森林砍伐面积相关联，并使用 Hansen 年度树木覆盖率损失数据来训练模型。最低阈值是像素清除率达到 25% 时才符合提醒条件，不过阈值因生态群组而异，以最大限度地减少误报。
以下是一个脚本示例，可用于快速了解 FORMA 数据集。
此图片包含产生 FORMA 提醒的阈值。这些值等于 max(25,40%*RegionalMax)，其中 RegionalMax 是相应生态群组中像素的历史最大清除量。
频段
像素大小 250 米
频段
名称
单位
最小值
最大值
像素尺寸
说明
delta_bound
%
25
40
米
触发 FORMA 提醒的阈值
使用条款
使用条款
FORMA 数据集可供用户随意使用或分发。WRI 要求用户适当注明出处，并在适用情况下将 WRI 和 GFW 标识为数据来源。
[null,null,[],[[["\u003cp\u003eThe FORMA dataset provides forest alert thresholds, derived from MODIS NDVI and FIRMS data, indicating potential forest clearing.\u003c/p\u003e\n"],["\u003cp\u003eWRI, the dataset provider, has discontinued FORMA alert updates in favor of Terra-i and GLAD due to their performance and user preference.\u003c/p\u003e\n"],["\u003cp\u003eThresholds, representing the percentage of pixel cleared, vary by ecogroup to minimize false positives and trigger alerts when exceeded.\u003c/p\u003e\n"],["\u003cp\u003eThe dataset covers the period from 2012-01-01 to 2016-01-01 and has a spatial resolution of 250 meters.\u003c/p\u003e\n"],["\u003cp\u003eFORMA data is freely available for use and distribution with proper attribution to WRI and GFW.\u003c/p\u003e\n"]]],[],null,["# FORMA Alert Thresholds\n\nDataset Availability\n: 2012-01-01T00:00:00Z--2016-01-01T00:00:00Z\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) [fire](/earth-engine/datasets/tags/fire) [forest](/earth-engine/datasets/tags/forest) [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\nThis image contains the thresholds at which, when crossed, a FORMA alert is\nproduced. The values are equal to max(25,40%\\*RegionalMax), where RegionalMax\nis the historical maximum clearing for a pixel in this ecogroup.\n\n### Bands\n\n\n**Pixel Size**\n\n250 meters\n\n**Bands**\n\n| Name | Units | Min | Max | Pixel Size | Description |\n|---------------|-------|-----|-----|------------|------------------------------------------------------------------|\n| `delta_bound` | % | 25 | 40 | meters | The thresholds at which, when crossed, a FORMA alert is produced |\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.Image('WRI/GFW/FORMA/thresholds');\nvar thresholds = dataset.select('delta_bound');\nvar visParams = {\n min: 0,\n max: 50,\n};\nMap.setCenter(26, -8, 3);\nMap.addLayer(thresholds, visParams, 'Thresholds for FORMA alerts');\n```\n[Open in Code Editor](https://code.earthengine.google.com/?scriptPath=Examples:Datasets/WRI/WRI_GFW_FORMA_thresholds) \n[FORMA Alert Thresholds](/earth-engine/datasets/catalog/WRI_GFW_FORMA_thresholds) \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/thresholds, daily,deforestation,fire,forest,forma,gfw,modis,monitoring,wri \n2012-01-01T00:00:00Z/2016-01-01T00:00:00Z \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_thresholds)"]]
