GEO4120c_workshop

GEO 4120c Workshop
Programs and Acquisition of Aerial Photography
2 February 2009

Introduction

Locating appropriate aerial photographs is a fundamental first step for many land mapping and evaluation projects, and aerial photos often form the basis for interpretation of other kinds of remote sensing. Many on-line sources for aerial photography exist for state and federal agencies as well as private companies. International sources are less available. On-line availability varies from simple descriptions with agency addresses to searchable databases with metadata, locality maps, and/or browse images. Metadata refers to data about the data, a necessary summary of the basic attributes of the imagery--film type, frame number, date, location, lens, etc.

A recent trend is to convert analog aerial photographs into raster images called digital orthophoto quads (DOQ). These images have been resampled to fit accurately onto a ground coordinate grid with very high pixel resolution--usually 1 or 2 m; they may be utilized for GIS in combination with other kinds of cartographic data. DOQs are now being created and tested for many regions of the United States.

See DOQ description.

U.S. Sources of Aerial Photography

Earth Science Information Centers (ESIC). Offices of the U.S. Geological Survey that provide national coverage for maps, aerial photographs, and many other databases.

Global Visualization (GLOVIS) browser by the USGS. Another way of finding imagery data and aerial photographs from the U.S. Geological Survey.

EarthExplorer. U.S. Geological Survey searchable catalog for all manner of cartographic and remotely sensed datasets.

Terraserver - Microsoft Corporation's vast collection of imagery and the innovative distribution hardware and software.

USDA Aerial Photography Field Office - the gateway to the National Agriculture Imagery Program (NAIP)

Florida Land Boundary Information System (LABINS) - gateway to DOQ of Florida

Terrafly - a new way to look at Earth
GoogleEarth - The most recent, killer app, way of looking at the Earth. Internet link is http://earth.google.com/ for information, but you can run the application from your Start-Programs button. Note that some areas have high-resolution (spatial) images, other areas do not. See if you can figure out a way to capture images from Google Earth.

Exercise

Search through web sites listed above to find answers to the following questions on the National Aerial Photography Program (NAPP), National High Altitude Photography (NHAP), and digital orthophoto quads (DOQ or DOQQ).

For each of these programs (ESIC, GLOVIS, EarthExplorer, Terraserver, USDA APFO, LABINS, Terrafly, GoogleEarth, NAPP, NHAP) describe VERY BRIEFLY the following USING YOUR OWN WORDS. Cut-and-paste downloads from the web sites will not be accepted.

What are each program's objectives?
Where is the source of the original aerial photos? (e.g. Terraserver uses one or more of the USGS acquistion programs).
What geographic and temporal extent do the program's aerial photos cover?
(NOTE: a "program" is defined by the agency and its objectives and usually, but not always, has the word "program" in the name, e.g. National Aerial Photography Program)

What are the nominal scale, flight altitude (above terrain), and lens focal length for NAPP photographs?
What are the nominal scale, flight altitude (above terrain), and lens focal length for NHAP photographs?
What kinds of film may be utilized for NAPP and NHAP photographs?
What does the term contract-acceptable flight specifications mean for aerial photography?
What are some of the standard NAPP and NHAP photographic products available to the public?
What is the typical ground spatial resolution (in m or ft) of NAPP and NHAP photographs?
What is the primary source of aerial photos for input to DOQs? What other sources may be used as inputs?
What is the typical ground spatial resolution for DOQ images? How does resolution on an aerial photo differ from resolution in a DOQ?
What kinds of information are contained in the header for a DOQ dataset?
What kinds of digital formats (media) may be utilized to supply DOQ datasets to the public?
What is a "world file," what does it do, and how does it work in the context of a DOQ? Give an example of a world file

Now attempt to locate aerial photography for your home region--city or county -- or some place in which you are interested. Search through web sites listed above and other sources you are able to find. You should identify an air photo to represent your city/county in both categories below.

Analog (conventional) aerial photograph.
Digital orthophoto quad--DOQ (or DOQQ).

For each of the two aerial photos, download the available information--metadata file, locality map, and/or browse image. Make sure to include the web address (URL) for each selected file. Briefly describe the characteristics and some possible applications (uses) for the aerial photos you selected.

Note: Do not order actual photographic prints or digital datasets.

Turn in to G:\share\GIS 4120c Aerial Photo Interepretation\your_folder\yourname_GEO4120_workshop_2.doc (note that you will create a new folder called "yourname" where yourname is your name so I can read the files easily). You will submit your assignments to this folder for the rest of the semester.

Written answers (questions 1-12 above) as a word processing file (e.g. .doc or .docx file).
Description of characteristics and applications for selected photos as a word processing file.
Digital files of metadata and images. I want to be able to look at the image.

Then send an e-mail to mbinford@geog.ufl.edu saying that you have turned in your project.