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.

## 数据集引言
1958年至1999年间，奥斯汀·波斯特（Austin Post）负责美国地质调查局（USGS）的北美冰川航空影像采集工作。本次采集的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。数据集的研究对象为北美冰川，此处提供的数字化产物旨在记录过去50余年间这些冰川发生的变化。本项目的核心目标是将这些胶片影像中的数据转换为数字化格式，以供未来对北美冰川变化开展分析使用。

## 数据包结构
1. 一级目录包含1964年至1997年的整体影像元数据集（nagapData.csv），以及用于检索与筛选数据的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3份按年代划分飞行路径信息的KML文件。
2. 二级目录（即当前层级）以影像拍摄年份命名，1964年至1997年间共有32个包含影像的年份文件夹。此类文件夹大多存储带有奥斯汀·波斯特标注的JPEG图像，同时还包含对应年份的专属CSV文件（YYYY.csv），其中收录了全年影像的元数据，包括拍摄日期、胶卷编号、地点名称、经度、纬度、海拔、介质类型及备注信息。整体数据集nagapData.csv即为各单个"YYYY.csv"文件的汇总。
3. 三级目录存储冰川影像：该层级的文件夹以相机胶卷编号（1、2等）和影像类型（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。此层级主要存储航空照片的图像文件，格式涵盖缩略图、JPEG或TIF；同时还包含针对每个胶卷的专属影像元数据CSV文件（包括拍摄日期、胶卷编号、地点名称、经度、纬度、海拔、介质类型及备注信息）、记录各影像专属相机参数的文本文件（info.txt），以及记录各影像专属色彩信息的文本文件（histo.txt）。