Photogrammetric scans of aerial photographs of North American glaciers, 1991

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.

引言：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。这些影像以垂直立体黑白影像为主，同时也收录了单张倾斜影像与彩色影像。本次数据集的研究对象为北美冰川，此处公开的数字化成果旨在记录过去50年间这些冰川发生的变化。本项目的目标是以数字化格式保存这些胶片影像中的数据，以供未来开展北美冰川变化相关研究使用。

数据包结构说明：
1. 一级目录包含1964年至1997年的数据集整体影像元数据（metadata）文件（nagapData.csv），以及一份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。此外还有三个按年代划分的飞行路径信息KML（Keyhole Markup Language）文件。
2. 二级目录（即当前层级）为影像拍摄年份，涵盖1964年至1997年的32个年份。多数文件夹内包含带有奥斯汀·波斯特标注说明的JPEG（Joint Photographic Experts Group）格式影像文件，同时还附带一份针对该年度的专属元数据CSV（Comma-Separated Values）文件（YYYY.csv，其中YYYY代表对应年份），其中包含全年影像的元数据信息，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。整体数据集文件（nagapData.csv）为各年度“YYYY.csv”文件的汇总集合。
3. 冰川影像位于三级目录。该层级的文件夹以相机胶卷编号（1、2等）与影像类型（缩略图、JPEG或TIFF（Tagged Image File Format））进行区分命名，部分文件夹还包含框标影像与倾斜影像子文件夹。本层级主要存储各类航空影像文件，格式包括缩略图、JPEG与TIFF。此外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）、一份记录各影像专属相机参数的文本文件（info.txt），以及一份记录各影像专属色彩信息的文本文件（histo.txt）。