Analyzing changes in habitat features at very large scales requires digital images with both high spatial and spectral resolutions. As part of an experiment to reduce blackbird (Icterinae) damage to sunflower, we used large-scale color-infrared photography to monitor regrowth of herbicide-treated cattail (Typha spp.) in wetlands used by roosting blackbirds. In this presentation we describe the methods used to collect, convert, interpret, and analyze high resolution images

Homan, H. Jeffrey

Linz, George M.

Penry, Linda B.

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln USDA National Wildlife Research Center - Staff Publications U.S. Department of Agriculture: Animal and Plant Health Inspection Service February 2003 Using Color-infrared Photography and GIS Using Color-infrared Photography and GIS H. Jeffrey Homan USDA, Wildlife Services, National Wildlife Research Center, Bismarck, ND Linda B. Penry USDA/APHIS/WS National Wildlife Research Center George M. Linz USDA/APHIS/WS National Wildlife Research Center, george.m.linz@aphis.usda.gov Follow this and additional works at: https://digitalcommons.unl.edu/icwdm_usdanwrc  Part of the Environmental Sciences Commons Homan, H. Jeffrey ; Penry, Linda B.; and Linz, George M., "Using Color-infrared Photography and GIS Using Color-infrared Photography and GIS" (2003). USDA National Wildlife Research Center - Staff Publications. 229. https://digitalcommons.unl.edu/icwdm_usdanwrc/229 This Article is brought to you for free and open access by the U.S. Department of Agriculture: Animal and Plant Health Inspection Service at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USDA National Wildlife Research Center - Staff Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Using Color-infrared Photography and GIS  to Quantify Cattail Coverage in Wetlands   H. Jeffrey Homan, Linda B. Penry, and George M. Linz USDA, Wildlife Services, National Wildlife Research Center, Bismarck, ND   Introduction  Analyzing changes in habitat features at very large scales requires digital images with both high spatial and spectral resolutions.  As part of an experiment to reduce blackbird (Icterinae) damage to sunflower, we used large-scale color-infrared photography to monitor regrowth of herbicide-treated cattail (Typha spp.) in wetlands used by roosting blackbirds.  In this presentation we describe the methods used to collect, convert, interpret, and analyze high resolution images.   Methods  Data Collection:  We used a SLR 35-mm camera loaded with Kodak Ektachrome® Professional Infrared EIR film.  The photographs were shot through a 24-mm lens.  A Wratten #12 filter and haze filter were attached to the lens to counteract blue light effects and improve clarity.  Film speed was set manually at EI 100, the recommended speed for the AR-5 developing process used for infrared accuracy.  Shutter speed and aperture settings were 1/500 sec and F-5.6, respectively.    We aerially photographed the wetlands at 460-610 m above ground level.  All photographs were taken vertically through a 38-cm diameter port in the floor of the plane’s fuselage.  To reduce distortion and shadowing of the ground features, photographs were taken nearly perpendicular to the wetlands on cloudless days from 1100 to 1400 h CT.   Data Conversion:  The developed images were scanned at 2100 pixels per inch (ppi) with a Polaroid® Sprint Scan 35 Plus.  The scans were converted to Tagged Image Format files.  File size was ~16 MB.    Data Interpretation:  We used ArcView® 3.2a software with the Image Analysis extension to categorize pixels into four habitat features through a supervised classification.  Ground truthing was used to determine the different habitats observed in the scanned images.  Living cattail was red, dead cattail was white or pale gray, open water was black, and floating vegetation was fluorescent blue.     1 Data Analyses:  Annual changes in proportions of living cattail, dead cattail, open water, and floating vegetation were tracked from 1999-2002.  A pixel-based coordinate system was used to coregister raster images of wetlands across years.  Changes in the proportions of categorized features were tracked through time by summarizing pixel counts between subplots in the wetlands.          Magnified view of wetland subplots.     Results  As seen in the images below, the herbicide treatments were applied in a north-south direction alternating with untreated lanes.  Over time, the treated cattail decayed, became submerged, and was replaced by open water; whereas, the untreated lanes maintained their structure except for 2001 when high water partially submerged the lanes.    1999    2 2000    2001     2002    3 In the tables below are results from one of five wetlands used in the experiment.  In this example the herbicide maintained its efficacy across all four years; however, the untreated lanes began to lose some integrity due in part to loss of cattail in the treated lanes.     Changes in percent composition of four habitat features in treated lanes from 1999-2002.  Treated Lanes  Year Live cattail Dead cattail Open water Floating vegetation 1999 1 59 40 0 2000 0 42 54 4 2001 0 6 93 1 2002 2 0 91 7      Changes in percent composition of four habitat features in untreated lanes from 1999-2002.  Untreated Lanes  Year Live cattail Dead cattail Open water Floating vegetation 1999 57 2 41 0 2000 26 30 43 1 2001 5 18 77 1 2002 18 1 73 8         4 Discussion  Although expensive and difficult to use, color-infrared film provides far better information for defining classes of vegetation than color slide film.  High spectral sensitivity is needed at large scales because minor inaccuracies in interpretation have profound impacts on the analysis.  In this experiment a ground cell resolution of ~1 m was obtained, which is considered a large scale in GIS analysis.  We have empirical evidence that the images could have been scanned at far less than 2100 ppi.  This would have saved on file size without any change in coverages of the habitat features.  The resolution of the slide film was in the 4000-5000 ppi range.  We consider 2100 ppi an acceptable compromise between file size and ground cell resolution.  By its nature, large-scale photography sacrifices areal coverage for spatial detail.  This method can only be applied when working on experiments with relatively small sample sizes.  In an average day of flying, we collected 20 images over a 4-hour shooting window; thus, large-scale photography is labor intensive and costly compared to the  15-30 m satellite images (e.g., Landsat) currently used in most GIS analyses.  However, several of our techniques to reduce blackbird damage are evaluated at a scale of    <100 km2.  At this scale, the methods described above are economically feasible while providing highly detailed data.               5 

Using Color-infrared Photography and GIS Using Color-infrared Photography and GIS

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
USDA National Wildlife Research Center - Staff 
Publications 
U.S. Department of Agriculture: Animal and 
Plant Health Inspection Service 
February 2003 
Using Color-infrared Photography and GIS Using Color-infrared 
Photography and GIS 
H. Jeffrey Homan 
USDA, Wildlife Services, National Wildlife Research Center, Bismarck, ND 
Linda B. Penry 
USDA/APHIS/WS National Wildlife Research Center 
George M. Linz 
USDA/APHIS/WS National Wildlife Research Center, george.m.linz@aphis.usda.gov 
Follow this and additional works at: https://digitalcommons.unl.edu/icwdm_usdanwrc 
 Part of the Environmental Sciences Commons 
Homan, H. Jeffrey ; Penry, Linda B.; and Linz, George M., "Using Color-infrared Photography and GIS Using 
Color-infrared Photography and GIS" (2003). USDA National Wildlife Research Center - Staff Publications. 
229. 
https://digitalcommons.unl.edu/icwdm_usdanwrc/229 
This Article is brought to you for free and open access by the U.S. Department of Agriculture: Animal and Plant Health 
Inspection Service at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USDA 
National Wildlife Research Center - Staff Publications by an authorized administrator of DigitalCommons@University 
of Nebraska - Lincoln. 
Using Color-infrared Photography and GIS  
to Quantify Cattail Coverage in Wetlands 
 
 
H. Jeffrey Homan, Linda B. Penry, and George M. Linz 
USDA, Wildlife Services, National Wildlife Research Center, Bismarck, ND 
 
 
Introduction 
 
Analyzing changes in habitat features at very large scales requires digital images with 
both high spatial and spectral resolutions.  As part of an experiment to reduce blackbird 
(Icterinae) damage to sunflower, we used large-scale color-infrared photography to 
monitor regrowth of herbicide-treated cattail (Typha spp.) in wetlands used by roosting 
blackbirds.  In this presentation we describe the methods used to collect, convert, 
interpret, and analyze high resolution images. 
 
 
Methods 
 
Data Collection:  We used a SLR 35-mm camera loaded with Kodak Ektachrome® 
Professional Infrared EIR film.  The photographs were shot through a 24-mm lens.  A 
Wratten #12 filter and haze filter were attached to the lens to counteract blue light 
effects and improve clarity.  Film speed was set manually at EI 100, the recommended 
speed for the AR-5 developing process used for infrared accuracy.  Shutter speed and 
aperture settings were 1/500 sec and F-5.6, respectively.   
 
We aerially photographed the wetlands at 460-610 m above 
ground level.  All photographs were taken vertically through a 
38-cm diameter port in the floor of the plane’s fuselage.  To 
reduce distortion and shadowing of the ground features, 
photographs were taken nearly perpendicular to the wetlands 
on cloudless days from 1100 to 1400 h CT.  
 
Data Conversion:  The developed images were scanned at 
2100 pixels per inch (ppi) with a Polaroid® Sprint Scan 35 
Plus.  The scans were converted to Tagged Image Format 
files.  File size was ~16 MB.   
 
Data Interpretation:  We used ArcView® 3.2a software with 
the Image Analysis extension to categorize pixels into four 
habitat features through a supervised classification.  Ground truthing was used to 
determine the different habitats observed in the scanned images.  Living cattail was red, 
dead cattail was white or pale gray, open water was black, and floating vegetation was 
fluorescent blue.   
 
 1 
Data Analyses:  Annual changes in proportions of living cattail, dead cattail, open water, 
and floating vegetation were tracked from 1999-2002.  A pixel-based coordinate system 
was used to coregister raster images of wetlands across years.  Changes in the 
proportions of categorized features were tracked through time by summarizing pixel 
counts between subplots in the wetlands. 
 
 
 
 
 
 
 
 
 
Magnified view of wetland subplots. 
 
 
 
 
Results 
 
As seen in the images below, the herbicide treatments were applied in a north-south 
direction alternating with untreated lanes.  Over time, the treated cattail decayed, 
became submerged, and was replaced by open water; whereas, the untreated lanes 
maintained their structure except for 2001 when high water partially submerged the 
lanes. 
 
 
 
1999 
 
 
 2 
2000 
 
 
 
2001 
 
 
 
 
2002 
 
 
 3 
In the tables below are results from one of five wetlands used in the experiment.  In this 
example the herbicide maintained its efficacy across all four years; however, the 
untreated lanes began to lose some integrity due in part to loss of cattail in the treated 
lanes. 
 
 
 
 
Changes in percent composition of four habitat features in treated lanes from 
1999-2002. 
 
Treated Lanes 
 
Year 
Live 
cattail 
Dead 
cattail 
Open 
water 
Floating 
vegetation 
1999 1 59 40 0 
2000 0 42 54 4 
2001 0 6 93 1 
2002 2 0 91 7 
 
 
 
 
 
Changes in percent composition of four habitat features in untreated lanes from 
1999-2002. 
 
Untreated Lanes 
 
Year 
Live 
cattail 
Dead 
cattail 
Open 
water 
Floating 
vegetation 
1999 57 2 41 0 
2000 26 30 43 1 
2001 5 18 77 1 
2002 18 1 73 8 
 
 
 
 
 
 
 
 4 
Discussion 
 
Although expensive and difficult to use, color-infrared film provides far better information 
for defining classes of vegetation than color slide film.  High spectral sensitivity is 
needed at large scales because minor inaccuracies in interpretation have profound 
impacts on the analysis.  In this experiment a ground cell resolution of ~1 m was 
obtained, which is considered a large scale in GIS analysis. 
 
We have empirical evidence that the images could have been scanned at far less than 
2100 ppi.  This would have saved on file size without any change in coverages of the 
habitat features.  The resolution of the slide film was in the 4000-5000 ppi range.  We 
consider 2100 ppi an acceptable compromise between file size and ground cell 
resolution. 
 
By its nature, large-scale photography sacrifices areal coverage for spatial detail.  This 
method can only be applied when working on experiments with relatively small sample 
sizes.  In an average day of flying, we collected 20 images over a 4-hour shooting 
window; thus, large-scale photography is labor intensive and costly compared to the  
15-30 m satellite images (e.g., Landsat) currently used in most GIS analyses.  However, 
several of our techniques to reduce blackbird damage are evaluated at a scale of    
<100 km2.  At this scale, the methods described above are economically feasible while 
providing highly detailed data.    
 
 
 
 
 
 
 
 
 
 
 5 


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Using Color-infrared Photography and GIS Using Color-infrared Photography and GIS

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