Tag Archives: imagery
There may be hundreds of thousands, if not millions, of undiscovered ancient sites across the globe, and Sarah Parcak wants to locate them. As a satellite archaeologist, she analyzes infrared imagery collected from far above the earth’s surface and identify subtle changes that signal a man-made presence hidden from view. Doing so, she and her colleagues aim to make invisible history visible once again—and to offer a new understanding of the past.
Collections of images
The recommended data structure within ArcGIS to manage and process imagery is the mosaic dataset. A mosaic structure enables significant big data capabilities for large, even massive, image collections. Each mosaic is composed of a number of related raster datasets, enabling you to keep your original individual image files on disk and to access them as part of a larger, integrated single collection. Mosaics are used to create a continuous image surface across large areas. For example, among other scenarios, you can use mosaics to handle coverage of very high-resolution image files for an entire continent. Or you can manage an entire historical map series for a nation for every year and every map scale. You can even manage huge multidimensional collections of time series information for earth observations and climate forecast modeling (often referred to as 4D). Creating mosaics is straightforward. You can point to a series of source georeferenced image files and automatically assemble a mosaic in minutes where each image acts as a tile within the collection.
Managing extremely large collections
GIS technology is both intuitive and cognitive. It combines powerful visualization and mapping with strong analytic and modeling tools. Remotely sensed earth observation—generally referred to in GIS circles simply as imagery—is the definitive visual reference at the heart of GIS. It provides the key—the geographic Rosetta stone that unlocks the mysteries of how the planet operates and brings it to life. When we see photos of Earth taken from above, we understand immediately what GIS is all about.
The story of imagery as an earth observation tool begins with photography, and in the early part of the twentieth century, photography underwent extraordinary changes and social adoption. Photos not only offered humanity a new, accessible kind of visual representation—they also offered a change in perspective. The use of color photography grew. Motion pictures and television evolved into what we know today. And humans took to the sky flying in airplanes, which, for the first time, enabled us to take pictures of the earth from above. It was a time of transformation in mapping and observation, providing an entirely new way of seeing the world.
World War II: Reconnaissance and intelligence gathering
During World War II, major advances in the use of imagery for intelligence were developed. The Allied Forces began to use offset photographs of the same area of interest, combining them to generate stereo photo pairs for enhancing their intelligence gathering activities. In one of many intelligence exercises called Operation Crossbow, pilots flying in planes—modified so heavily for photo gathering that there was no room for weapons—captured thousands of photographs over enemy-held territory. These resulting collections required interpretation and analysis of hundreds of thousands of stereo-photographic pairs by intelligence analysts.
Using elevation to enable accurate image georeferencing
Imagery has an amazing amount of information, but raw aerial or satellite imagery cannot be used in a GIS until it has been processed such that all pixels are in an accurate (x,y) position on the ground. Photogrammetry is a discipline, developed over many decades, for processing imagery to generate accurately georeferenced images, referred to as orthorectified images (or sometimes simply orthoimages). Orthorectified images have been processed to apply corrections for optical distortions from the sensor system, and apparent changes in the position of ground objects caused by the perspective of the sensor view angle and ground terrain.
An Expanding Collaboration Between the USDA Forest Service and Esri
By John Steffenson
You may know the USDA Forest Service as the steward of 193 million acres of national forest land, but the agency is much more than that. Its Research and Development (R&D) branch is the largest forestry research organization in the world, charged since 1928 with a congressional mandate to make “a comprehensive survey of the present and prospective requirements for timber and other forest products of the United States.” The branch’s Forest Inventory and Analysis (FIA) program drives the survey that meets that mandate.
Surveying the nation’s forests involves maintaining 355,000 permanent sample locations on private and public lands across nine time zones from Guam to the Caribbean and monitoring a grid of approximately 6.5 million photo points. While the traditional focus has been on rural forest land, the FIA program is expanding to include urban forest resources. They also survey private land owners and wood-processing facilities across the country to understand the flow of wood products from state to state and to international customers.
Drone2Map Turns Your Drone Into an Enterprise Productivity Tool
A new desktop app from Esri turns raw still imagery captured by drones into professional 2D and 3D imagery products. Drone2Map for ArcGIS means that affordable imagery is available on demand for land analysis, infrastructure inspection, and monitoring events such as natural disasters and environmental changes.
“Drones are an emerging technology with the potential to revolutionize how we work across many industries,” said Esri president Jack Dangermond, who announced the beta release of Drone2Map for ArcGIS at the Esri Federal GIS Conference earlier this month in Washington, DC. “We built Drone2Map for ArcGIS to give people the ability to process, use, and share imagery — all within ArcGIS.” Continue reading
Last Update: December 10, 2015 In early January of 2014, we heard quite a bit about the polar vortex (not a new term, by the way) as North America struggled with some of the most frigid and dangerous temperatures seen … Continue reading
The outbreak of bad weather that has plagued the US over the past few weeks has created a significant need for access to location data and pre- and post-event map imagery. I was recently on a call with a former colleague who was looking for the latest post-event imagery. He described how imagery and other recently available features of ArcGIS Online, Esri’s cloud-based mapping platform, were having a significant impact on streamlining their claims workflow and efforts to effectively align field resources. Continue reading
Atlases have long been used by people to help navigate and understand our world. A traditional atlas consists of a collection of static maps portraying various aspects of geography, bound together in book form and updated with new information at long intervals. The geography covered, in terms of both themes and extent, is set in stone for any given atlas, and the thematic information is typically created and authored by a select few authoritative sources.
These traditional atlases have served us well for many hundreds of years. But today, the world is changing rapidly, and it’s difficult for traditional atlases to keep up with the pace of that change. To help us keep pace with our evolving planet, our concept of what exactly constitutes an atlas must also evolve. Continue reading