Tree Canopy 2022

This dataset was created to depict approximate tree canopy cover for all land within the City of Austin's "full watershed regulation area." Intended for planning purposes and measuring citywide percent canopy.

Definition: Tree canopy is defined as the layer of leaves, branches, and stems of trees that cover the ground when viewed from above.

Methods: The 2022 tree canopy layer was derived from satellite imagery (Maxar) and aerial imagery (NAIP). Images were used to extract tree canopy into GIS vector features. First, a “visual recognition engine” generated the vector features. The engine used machine learning algorithms to detect and label image pixels as tree canopy. Then using prior knowledge of feature geometries, more modeling algorithms were used to predict and transform probability maps of labeled pixels into finished vector polygons depicting tree canopy. The resulting features were reviewed and edited through manual interpretation by GIS professionals. When appropriate, NAIP 2022 aerial imagery supplemented satellite images that had cloud cover, and a manual editing process made sure tree canopy represented 2022 conditions. Finally, an independent accuracy assessment was performed by the City of Austin and the Texas A&M Forest Service for quality assurance. GIS professionals assessed agreement between the tree canopy data and its source satellite imagery. An overall accuracy of 98% was found. Only 23 errors were found out of a total 1,000 locations reviewed. These were mostly omission errors (e.g. not including canopy in this dataset when canopy is shown in the satellite or aerial image). Best efforts were made to ensure ground-truth locations contained a tree on the ground. To ensure this, location data were used from City of Austin and Texas A&M Forest Service databases.

Analysis: The City of Austin measures tree canopy using the calculation: acres of tree canopy divided by acres of land. The area of interest for the land acres is evaluated at the City of Austin's jurisdiction including Full Purpose, Limited Purpose, and Extraterritorial jurisdictions as of May 2023. New data show, in 2022, tree canopy covered 41% of the total land area within Austin's city limits (using city limit boundaries May 2023 and included in the download as layer name "city_of_austin_2023"). 160,046.50 canopy acres (2022) / 395,037.53 land acres = 40.51% ~41%. This compares to 36% last measured in 2018, and a historical average that’s also hovered around 36%. The time period between 2018 and 2022 saw a 5 percentage point change resulting in over 19K acres of canopy gained (estimated).

Data Disclaimer: It's possible changes in percent canopy over the years is due to annexation and improved data methods (e.g. higher resolution imagery, AI, software used, etc.) in addition to actual in changes in tree canopy cover on the ground. For planning purposes only. Dataset does not account for individual trees, tree species nor any metric for tree canopy height.

Tree canopy data is provided in vector GIS format housed in a Geodatabase. Download and unzip the folder to get started. Please note, errors may exist in this dataset due to the variation in species composition and land use found across the study area. This product is for informational purposes and may not have been prepared for or be suitable for legal, engineering, or surveying purposes. It does not represent an on-the-ground survey and represents only the approximate relative location of property boundaries.

This product has been produced by the City of Austin for the sole purpose of geographic reference. No warranty is made by the City of Austin regarding specific accuracy or completeness.

Data Provider: Ecopia AI Tech Corporation and PlanIT Geo, Inc.
Data derived from Maxar Technologies, Inc. and USDA NAIP imagery

本数据集旨在描绘奥斯汀市全流域管理区域范围内所有土地的大致树冠覆盖率。该数据集旨在为城市规划目的和衡量全市树冠覆盖率提供参考。

定义：树冠系指从上方观察时覆盖地面的树木叶片、枝条和树干层。

方法：2022年的树冠层是通过卫星影像（Maxar）和航空影像（NAIP）生成的。利用这些影像提取树冠信息并转化为GIS矢量特征。首先，通过“视觉识别引擎”生成矢量特征，该引擎运用机器学习算法检测并标记图像像素作为树冠。随后，利用对特征几何形状的先验知识，进一步运用建模算法将标记像素的概率图预测并转化为描绘树冠的最终矢量多边形。生成的特征通过GIS专业人士的逐个审查和编辑。在适当的情况下，使用2022年的NAIP航空影像补充了有云层的卫星影像，并通过人工编辑过程确保树冠反映了2022年的状况。最终，奥斯汀市和德克萨斯A&M森林服务局对数据进行了独立准确性评估，以确保数据质量。GIS专业人士评估了树冠数据与其来源卫星影像之间的一致性。整体准确率达到98%。在审查的1000个位置中，仅发现23处错误。这些错误主要是遗漏错误（例如，在卫星或航空图像中显示树冠时，未将该树冠包含在本数据集中）。为确保地面真实位置包含树木，尽力确保了地面真实位置的有效性。为此，使用了奥斯汀市和德克萨斯A&M森林服务局数据库的位置数据。

分析：奥斯汀市使用以下计算方法衡量树冠：树冠面积英亩数除以土地面积英亩数。对土地面积的评估以奥斯汀市截至2023年5月的管辖范围（包括全面目的、有限目的和地区管辖权）为基础。新数据显示，2022年，树冠覆盖了奥斯汀市市区总面积的41%（使用2023年5月的市区界限，并作为“city_of_austin_2023”图层包含在下载中）。160,046.50英亩树冠面积（2022）/ 395,037.53英亩土地面积 = 40.51% ~41%。这与2018年测量的36%相比，以及历史平均值也徘徊在36%左右。2018年至2022年期间，变化了5个百分点，导致超过19K英亩的树冠面积增加（估计值）。

数据免责声明：多年以来树冠覆盖率的变化可能是由于并吞和改进的数据方法（例如，更高分辨率的影像、AI、软件使用等）以及实际地面树冠覆盖的变化。仅用于规划目的。本数据集不考虑个别树木、树种以及树冠高度的相关指标。

树冠数据以矢量GIS格式提供，存放在地理数据库中。下载并解压缩文件夹以开始使用。请注意，由于研究区域内物种组成和土地利用的变化，本数据集中可能存在错误。本产品仅供信息参考，可能不适用于法律、工程或测量目的。它不代表地面调查，仅代表财产边界的大致相对位置。

本产品由奥斯汀市制作，仅用于地理参考。奥斯汀市不对特定准确性或完整性作出保证。

数据提供方：Ecopia AI Tech Corporation 和 PlanIT Geo, Inc。
数据来源于Maxar Technologies, Inc. 和美国农业部NAIP影像