Photogrammetric scans of aerial photographs of North American glaciers, 1988. Roll 1 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 csv (APFileIndex.csv) with information about these jpegs, and 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). 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.

简介：1958年至1999年间，奥斯丁·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影像为主，同时亦收录了单张倾斜影像与彩色影像。本数据集以北美冰川为观测对象，此处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。本项目的核心目标是将这些胶片影像中的数据以数字化形式永久留存，以供未来开展北美冰川变化相关研究分析。

文件结构说明：
1. 一级目录包含1964年至1997年的图像元数据总集（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目录内容。此外还包含三个按年代划分飞行路径信息的KML（Keyhole Markup Language）文件。
2. 二级目录为影像拍摄年份。本次数据集涵盖1964年至1997年的32个拍摄年份。多数此类目录内包含奥斯丁·波斯特标注说明的JPEG（Joint Photographic Experts Group）图像文件，同时还配有一份记录这些JPEG图像信息的CSV文件（APFileIndex.csv），以及一份年度专属CSV文件（YYYY.csv），其中存储了全年的图像元数据，包括拍摄日期、胶卷编号、地点名称、经度、纬度、海拔高度、介质类型与备注信息。总集文件nagapData.csv即为所有单个YYYY.csv文件的汇总。
3. 冰川影像存储于三级目录（即当前层级）。该层级的目录以相机胶卷编号（1、2等）与图像类型（缩略图、JPEG或TIFF（Tagged Image File Format））进行区分。本层级主要包含航空影像的各类图像文件，格式涵盖缩略图、JPEG与TIFF。此外还配有一份针对每个胶卷的专属元数据CSV文件，其中包含拍摄日期、胶卷编号、地点名称、经度、纬度、海拔高度、介质类型与备注信息；另有一份存储单张相机专属参数的文本文件（info.txt），以及一份存储单张图像专属色彩信息的文本文件（histo.txt）。