Interferometric Synthetic Aperture Radar (IFSAR) Alaska

The U.S. Geological Survey (USGS) National Geospatial Program (NGP) developed the Alaska Mapping Initiative (AMI) to collaborate with State and other Federal partners in Alaska to acquire 3-dimensional elevation data to improve statewide topographic mapping products. AMI coordinates Federal activities through the Alaska Mapping Executive Committee (AMEC) and State efforts through Alaskas Statewide Digital Mapping Initiative (SDMI) to ensure a unified approach for consistent data acquisition and enhancement of elevation data products. AMI attained interferometric synthetic aperture radar (IFSAR) data to generate Digital Elevation Models (DEMs). This radar mapping technology is an effective tool for collecting data under challenging circumstances such as cloud cover, extreme weather conditions, rugged terrain, and remote locations. Airborne IFSAR data were flown over southcentral Alaska in summer 2010 and over northwestern Alaska in 2012. Additional areas may become available as projects are inspected for quality and released for dissemination. A coverage map in EarthExplorer indicates the extent of distributable data. IFSAR Alaska Products Elevation products generated from IFSAR data include Digital Surface Model (DSM) and Digital Terrain Model (DTM) data. DSMs provide elevation values of landscape features on the earths surface. This topographic product contains the height of the highest surface on the ground including vegetation, manmade structures, and bare earth. DTMs provide elevation values of the underlying terrain of the earths surface. This topographic product reflects the height of bare earth where the elevations of vegetation and manmade features have been removed. The USGS Earth Resources Observation and Science (EROS) Center distributes IFSAR Alaska products in Georeferenced Tagged Image File Format (GeoTIFF). The pixel values for the grayscale images represent elevation numbers.

美国地质调查局（U.S. Geological Survey, USGS）国家地理空间项目（National Geospatial Program, NGP）发起阿拉斯加测绘倡议（Alaska Mapping Initiative, AMI），旨在与阿拉斯加州内的州政府及其他联邦合作伙伴协作，获取三维高程数据以优化全州范围的地形测绘产品。
AMI通过阿拉斯加测绘执行委员会（Alaska Mapping Executive Committee, AMEC）统筹联邦相关工作，通过阿拉斯加州全域数字测绘倡议（Alaska's Statewide Digital Mapping Initiative, SDMI）协调州内事务，确保在高程数据采集与产品优化工作中采用统一规范的方法。
AMI获取了干涉合成孔径雷达（interferometric synthetic aperture radar, IFSAR）数据，用于生成数字高程模型（Digital Elevation Models, DEMs）。
该雷达测绘技术是应对复杂场景的高效工具，可在多云覆盖、极端天气、崎岖地形及偏远区域等数据采集难度较大的环境下开展数据收集工作。
机载IFSAR数据分别于2010年夏季采集覆盖阿拉斯加中南部区域，2012年采集覆盖阿拉斯加西北部区域。
随着更多项目通过质量审核并获准公开分发，后续可获取的数据覆盖范围将进一步拓展。
EarthExplorer平台提供的覆盖范围地图可查询可分发数据的覆盖区域。
IFSAR阿拉斯加产品：由IFSAR数据生成的高程产品包括数字地表模型（Digital Surface Model, DSM）与数字地形模型（Digital Terrain Model, DTM）数据。
数字地表模型（DSM）提供地球表面各类景观要素的高程值，该地形产品包含地面上最高地表的高度信息，涵盖植被、人工构筑物以及裸土。
数字地形模型（DTM）提供地球表面基底地形的高程值，该地形产品反映去除植被与人工构筑物高度后的裸土高程。
美国地质调查局地球资源观测与科学中心（Earth Resources Observation and Science, EROS）以地理标记图像文件格式（Georeferenced Tagged Image File Format, GeoTIFF）分发IFSAR阿拉斯加系列产品，其灰度图像的像素值代表高程数值。