Photogrammetric scans of aerial photographs of North American glaciers, 1979. Roll 2 jpegs

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. File 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 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 (this 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 or matchReport.txt) with color information and scanner specifications 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。该数据集以垂直立体黑白航空影像为主，同时收录了单张倾斜航空影像与彩色航空影像。数据集以北美冰川为拍摄对象，本次公开的数字化成果旨在记录近50年来北美冰川的变化情况。本项目旨在将这些胶片影像中的原始数据以数字化格式留存，为后续开展北美冰川变化相关研究提供支撑。

**文件布局**
1. **第一层级**：包含1964年至1997年的全数据集影像元数据文件（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完整的文件结构与文件夹内容；此外还包含3份按年代划分飞行路径信息的KML（Keyhole Markup Language）文件。
2. **第二层级**：以影像拍摄年份作为文件夹分类依据，共涵盖1964年至1997年的32个拍摄年份。此类文件夹大多包含奥斯汀·波斯特标注说明的JPEG（Joint Photographic Experts Group）影像，同时还附带一份对应年份的专属元数据CSV文件（YYYY.csv），其中记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。全数据集文件（nagapData.csv）即为各单年度"YYYY.csv"文件的聚合汇总。
3. **第三层级（即当前层级）**：存放冰川影像文件。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））进行分类，部分文件夹还额外包含框标影像与倾斜影像子文件夹。本层级主要包含航空照片的影像文件，格式涵盖缩略图、JPEG或TIFF。此外还包含三类配套文件：一是针对各胶卷的专属影像元数据CSV文件（涵盖拍摄日期、胶卷编号、地点名称、经度、纬度、海拔、介质类型与备注信息）；二是一份记录各影像专属相机参数的文本文件（info.txt）；三是一份记录各影像专属色彩信息与扫描仪参数的文本文件（histo.txt或matchReport.txt）。