Photogrammetric scans of aerial photographs of North American glaciers, 1988

Introduction: Between 1958 and 1999, Austin Post led the USGS collection of aerial imagery of North American glaciers. These images are primarily vertical stereo black and white images, although single oblique images, as well as color images have been collected. The glaciers of North America were the subjects, and the digital products made available here serve to document the changes that have occurred to the glaciers over the past 5 decades. The purpose of this project is to preserve the data contained within these film images in a digital format for future analysis of North American glacier change. Package Layout: 1. The first level contains an overall data set of image metadata from 1964 - 1997 (nagapData.csv) and an R script (searchData.R) with instructions on how to search and subset the data. fileLayout.pdf shows the file structure and folder contents visually. There are also three kml files with flight path information by decade. 2. The second level (this level) is the year in which the pictures were taken. There are 32 years with images from 1964 – 1997. The majority of these folders are jpegs with notes provided by Austin Post. They also contain a year-specific csv (YYYY.csv) that contains image metadata for the entire year (date, roll numbers, location name, longitude, latitude, altitude, media, and comments). The overall data set (nagapData.csv) is the aggregate of each individual “YYYY.csv” file. 3. The glacier photos are located at the third level. The folders at this level are distinguished by camera roll number (1, 2, etc.), and image type (thumbnail, jpeg, or tif); some also contain fiducial and oblique image folders. This level primarily contains image files of aerial photos as either thumbnails, jpegs, or tifs. It also includes a csv with image metadata specific to each roll (date, roll numbers, location name, longitude, latitude, altitude, media, and comments), a text file (info.txt) with camera specifications unique to each image, and a text file (histo.txt) with color information unique to each image.

数据集简介：1958年至1999年间，奥斯汀·波斯特（Austin Post）主持了美国地质调查局（United States Geological Survey, USGS）的北美冰川航空影像采集工作。该系列影像以垂直立体黑白航空影像为主，同时涵盖单张倾斜影像与彩色影像。数据集以北美冰川为研究主体，此处公开的数字化成果用于记录近50年来这些冰川的演变情况。本项目旨在将这些胶片影像中的数据以数字化格式永久保存，以供未来开展北美冰川变化相关研究分析使用。

数据包文件结构：
1. 第一层级包含1964年至1997年的数据集整体影像元数据文件（nagapData.csv），以及用于指导数据检索与子集提取的R脚本（searchData.R）。fileLayout.pdf以可视化形式展示了文件结构与文件夹内容；另有三份按年代划分飞行路径信息的KML文件（Keyhole Markup Language）。
2. 第二层级（即当前层级）为影像拍摄年份。1964年至1997年间共有32个年份包含影像数据。大部分此类文件夹内存储了附带奥斯汀·波斯特标注的JPEG（联合图像专家组格式，Joint Photographic Experts Group）文件，同时还包含对应年份的专属元数据CSV文件（YYYY.csv，其中YYYY为具体拍摄年份），该文件收录了全年影像的完整元数据，包括拍摄日期、胶卷编号、地点名称、经度、纬度、海拔、介质类型与备注信息。整体数据集文件nagapData.csv即由各单个“YYYY.csv”文件聚合整合而成。
3. 冰川影像存储于第三层级。该层级的文件夹以相机胶卷编号（如1、2等）与影像类型（缩略图、JPEG或TIFF（标签图像文件格式，Tag Image File Format））进行分类命名，部分文件夹还包含框标影像与倾斜影像的子文件夹。本层级主要存储各类航空影像文件，格式涵盖缩略图、JPEG与TIFF；同时还包含针对每个胶卷的专属影像元数据CSV文件（包含拍摄日期、胶卷编号、地点名称、经度、纬度、海拔、介质类型与备注）、记录单张影像专属相机参数的文本文件（info.txt），以及记录单张影像专属色彩信息的文本文件（histo.txt）。