Photogrammetric scans of aerial photographs of North American glaciers, 1969. Roll 2 tiffs

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）主导了美国地质调查局（United States Geological Survey, USGS）的北美冰川航空影像采集工作。这批影像以垂直立体黑白影像为主，同时也采集了单张倾斜影像与彩色影像。本数据集以北美洲冰川为研究对象，此处提供的数字化产品旨在记录过去50年来这些冰川发生的变化。本项目的核心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分析使用。

文件结构：
1. 一级目录包含1964年至1997年的影像元数据总数据集（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整体文件结构与文件夹内容。此外还有三份按十年划分的飞行路径信息KML文件。
2. 二级目录以影像拍摄年份命名，涵盖1964年至1997年的32个年份。大部分文件夹内包含带有奥斯汀·波斯特标注说明的JPEG图片，同时还会附带一份对应年度的专属元数据CSV文件（YYYY.csv，其中YYYY为对应年份），其中包含全年影像的完整元数据信息，包括拍摄日期、胶卷编号、地点名称、经度、纬度、海拔、介质类型与备注信息。总数据集nagapData.csv为各年度YYYY.csv文件的聚合汇总。
3. 冰川影像存储于三级目录（即当前层级）。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TIF）进行区分，部分文件夹还包含框标影像与倾斜影像子文件夹。本层级主要包含航空照片的影像文件，格式涵盖缩略图、JPEG或TIF。此外还会附带一份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、介质类型与备注信息）、一份记录各影像专属相机参数的文本文件（info.txt），以及一份包含色彩信息与扫描仪专属参数的文本文件（histo.txt或matchReport.txt）。