Using the Iowa 2002 Color-infrared Digital Orthophoto Collection
James D. Giglierano
Presentation for 2003
July 1, 2003 (July 8 Update)
The purpose of this presentation
is to acquaint new users of color-infrared digital orthophotography with the
extended spectral capabilities of this media.
Many users may be more familiar with standard black and white
orthophotography available through the USGS Digital Orthophotography program (DOQQ)
or with high resolution black and white orthophotos acquired by many
Overview of Iowa CIR
program: The acquisition of
color-infrared aerial photography in the spring of 2002 and subsequent
production of one meter digital orthophoto quarter quadrangles (DOQQs) was
funded by a partnership of more than 45 federal, state and local agencies,
private companies and non-profit organizations.
The project was coordinated through the Iowa Geographic Information
Council’s Remote Sensing Committee and managed by the Iowa Department of
Natural Resources. Color-infrared aerial
photography with airborne GPS and ground control was acquired by Northwest
Overview of Primary Products:
Overview of Ancillary Products:
These ancillary products will be available in August 2003 from IGS ftp site at ftp://ftp.igsb.uiowa.edu/pub/download/CIR2002.
Using the collection: Because the color-infrared aerials photos were taken over a period of two months (see attached map), the infrared response of the vegetation will vary considerably, thus producing a wide range of pinks and reds on the film and digital products. Quarter quadrangles products are made from a single image so vegetation response is consistent across the DOQQ, but county mosaics will display varying vegetation response due to the combination of images acquired on several dates. By displaying an overlay of the polygon shape file of frame outlines with the photo dates on top of the digital mosaics, one can see which image dates contributed to the overall product. This usually reveals why pinks and reds may appear stronger in one area of the image while more subdued elsewhere.
The ancillary point and polygon shape files for the airphoto frames and othophoto tiles also have information on the time of day the photography was acquired. This will help a person viewing the images to interpret shadow lengths and directions, or decipher other instances where time of day may be a clue to what was happening at the time the film was exposed (such as a full parking lot of cars).
The ground truth point file and associated digital still photography can be used to look up what various types of vegetation may look like, both on the ground or from the aerial images. The main focus of the ground truth collection was vegetation, about half the sites being permanent vegetation (prairie grasses, forest, pasture/hayland) and the rest being cropland.
The climate files include records
of precipitation from weather stations and radar, snowfall, air and soil
temperature, and clouds from various weather satellite images. The main use of this information is to give
the person using the airphoto collection an idea of the weather conditions on
the day of the flight or the week or so leading up the flight. For example, many years from now a person
looking at the photos might not realize that that a major snow storm took place
on “April Fool’s Day” that dropped several inches of snow on the north-eastern
Secondary Data Products: As time goes by and more and more projects use the Iowa 2002 CIR Digital Orthophoto Collection, GIS data files derived from the collection will become available to users. Currently, the collection is being used to develop a road centerline file by Iowa DOT, an inventory of animal confinement operations by Iowa DNR, common land unit boundaries by USDA Farm Service Agency, and a statewide land use inventory by IDNR.