Ground truthing (gps point taking) of invasive species and land use in Cimarron County, Oklahoma and Union County New Mexico.

1. Ground truthing is an important, however tedious, step to assessing the accuracy of landsat data
classifications and other remotely sensing imagery. Conducting fieldwork allows for the researcher to
gather information that is unavailable with remotely sensed imagery. For instance, the 2001 and 2011
National Land Cover Datasets has a resolution that does not allow for smaller features to be seen. This
type of fieldwork requires a lot of time, patience, and a good eye to differentiate land cover types.
Accuracy assessments of the ground truth data indicate that this method of data gathering is fairly
accurate and reliable. The data collection method of ground truthing can be improved with a more
strategic protocol of collection in the field, and perhaps with more time and freedom involving future
research, this method can become even more accurate.
Scope
The scope of this project involved ground truthing various land cover types in Union County, New
Mexico and Cimarron County, Oklahoma. By utilizing public roadways, our task was to ground truth
the region in two separate vehicles and cover as many different topographical landmarks as possible.
Limitations
Access was limited to public roadways. Private property was off limits and all data had to be
collected on the road and required significant amounts of estimation, such as the depth of the land cover
type. In addition, collection had to occur during the day with the additional limitation of the fall season
shortening daylight. The time allotted to acquire such a vast amount of data in the region was limited to
only two days which required quicker and perhaps less accurate methods of collection. This also limited
travel in the larger of the two counties, Union County.
Limitations involving data analysis included the age of the National Land Cover Dataset. We were
conducting an analysis on a classified image that is from 2011. The gap in image age could have skewed
the accuracy assessment results.
Ground Truthing Invasive Species in Cimarron County, OK and Union
County, NM
Anthony Pennington, Austin Fessler, Giovanni Penna, Hayden Harrison, Kayla King, Zach Robinson
Introduction
Background
Methodology
Recently, there has been an influx of invasive species of vegetation such as the Cholla Cactus
(Cylindropuntia imbricata) and Pinyon-Juniper Woodlands (Pinus edulis/Juniperus grandis) in Cimarron
County, Oklahoma and Union County, New Mexico. This study gathered ground truthing points to create a
database for analysis in order to analyze this change. The ground truthing samples were collected via GPS
in order to record land cover across the region. The goal of the study was to identify the spread of invasive
species, mainly woody plant encroachment, and to compare the ground truth points with the 2011 National
Land Cover Dataset. This was mostly looking at the conversion of grasslands into irrigated agricultural
farmland and shrubland. We compared our findings with 2011 National Land Cover Dataset and conducted
an accuracy analysis and a land cover change analysis.
Group of Juniper in Cimarron County, Oklahoma Salt Cedar across the Cimarron River Cimarron
County, Oklahoma
Scattered Cholla in Cimarron County, Oklahoma
Citations
Anadon, J. D., Sala, O., Turner, B. L., & Bennett, E. M. (2014). “Effect of woody-plant encroachment on livestock production in North and South America”. Proceedings of the
National Academy of Sciences of the United States of America, 11(35), pp. 12949
Carpenter, A.T. 1998. “Element Stewardship Abstract for Tamarisk.” The Nature Conservancy Wildland Weed Database.
Eastman, J Ronald. 2015. "TerrSet manual." Accessed in TerrSet version 18:1-390.
Fagin, T., Vadjunec, J., Colston, N., Wenger, K., & Graham, A. (2016) “Land tenure and landscape change: a comparison of public-private lands in the southern High Plains”.
Ecological Processes.
Hargrave, Michael L. 2006. "Ground truthing the results of geophysical surveys." Remote sensing in archaeology: an explicitly North American perspective:269-304.
Story, Michael, and Russell G Congalton. 1986. "Accuracy assessment: a user’s perspective." Photogrammetric Engineering and remote sensing 52 (3):397-399.
Verne, Grant and Karen A. Grant. June 7, 1971. “Natural Hybridization between the Cholla Cactus Species Opuntia spinosior and Opuntia versicolor.” Department of Botany,
University of Texas.
White, John P. Diane Pub Co, 2004. “Ecology, diversity and sustainability of the middle Rio Grande basin.”
Acknowledgements
This student fieldwork experience has been funded in part by a National Science Foundation (NSF) research grant (#CMMI-1266381:
Vadjunec, Phillips, & Fagin). Any opinions and findings are those of the authors and not NSF.
Citations & Acknowledgements
National Land Cover Dataset (simplified) Legend
Deciduous Forest
Ground Truthing Points Across Union County, New Mexico
Results
Ground Truthing Points Across Cimarron County, Oklahoma
Grassland/Herbaceous
Cultivated Crops
Developed
Barren Land
Evergreen Forest
Shrubland
Open Water
Discussion
Cimarron County Accuracy Assessment Results
Conclusions
Classification Percent Accurate Total Percent Accurate
Barren Land 20%
64%
Cultivated Crops 100%
Deciduous Forest 0%
Developed 83%
Evergreen Forest 14%
Grassland/Herbaceous 96%
Open Water 100%
Shrub/Scrub 100%
Scope and Limitations
Classification Percent Accurate Total Percent Accurate
Barren Land 100%
69%
Cultivated Crops 73%
Developed 100%
Evergreen Forest 0%
Grassland/Herbaceous 82%
Open Water 100%
Shrub/Scrub 29%
Union County Accuracy Assessment Results
Land Cover Change Assessment from 2001 to 2011
Center Pivot Irrigation in Union County, New Mexico
The accuracy assessment conducted on the ground truth points recorded in Union County, NM and
Cimarron County, OK reveal a 64% and 69% accuracy rate, respectively. In Union County, land cover
types such as cultivated crops, open water, and shrubland were recorded with 100% accuracy. Other
land cover types, such as developed and grassland/herbaceous areas, were recorded with an accuracy of
83% and 96%, respectively. In Cimarron County, land cover types such as barren land, developed, and
open water were recorded with 100% accuracy. Other land cover types, such as cultivated crops and
grassland/herbaceous areas, were recorded at an accuracy level of 73% and 82%, respectively.
Together, the accuracy assessment revealed a 62% accuracy in the ground truth points recorded between
both counties. In both Cimarron County and Union County, the land cover types of evergreen forests
had an accuracy assessment percentage of 0% and 14%, respectively. This could be due to the age of the
2011 NLCD data as this land cover type looked to be relatively new.
The land cover change assessment from 2001 to 2011 indicated large areas of stable land cover
across both Cimarron County, OK and Union County, NM. The land cover change results show areas of
change from grassland/herbaceous to cultivated crops. Areas in blue show change from
grassland/herbaceous to cultivated crops. Areas that experienced change from grassland/herbaceous to
shrubland can be seen in pink.
Land Cover Change Assessment Legend
Stable Shrubland
Grassland/Herbaceous to
Shrubland
Stable Grassland/
Herbaceous
Other
Stable Cultivated Crops
Grassland/Herbaceous to
Cultivated Crops
An example of Yucca in Union County, New Mexico Clayton Lake, Union County, New Mexico
In Cimarron and Union counties, woody plant encroachment has created a number of issues regarding
the effect of the invasive species in the region. Ground cover is being taken over, pushing out native grass
species and reducing the area these grasses can grow in. We believe overgrazing and pasture conversion of
fields in the region are a primary factor in the encroachment of these invasive species. In comparing the
ground truthing points to the NLCD data for the two counties, we assessed the accuracy of said data as well
as conducted a land cover change analysis.
Cholla Shrubland
Most commonly found in the deserts of North America, the cholla cactus has more than twenty species in
the Optunia genus of the Cactacea family. The flowers have a green to yellowish color which sometimes
can be orange. The species thrives mostly in the months of April through June and are most commonly
located in the deserts of Southwest America with a variety of species inhabiting these deserts. The species
locations are often based on elevation and other vegetation that is present. Cholla species prefer dry soil in
areas that resemble steppes, but some species have adapted to forested areas with most being located in dry
rocky areas.
Pinyon-Juniper Shrubland/Woodland
Pinyon-Juniper woodlands are one of the largest ecosystems in the Southwest and in the Middle Rio
Grande Basin (White 2004). The tree has historically been used as a natural resource. Pinyon-Juniper are
trees that are relatively small and average around five meters in height. The Pinyon-Juniper has different
species compositions. The tree sometimes is composed of dense areas that are relatively large in height,
while other areas have more spread out populations that are shorter in height. In New Mexico alone, there
are hundreds of pinyon species. This type of woodlands suffers from a variety of damaging agents such as
insects and invasive species of plants and trees.
In order to assess the Landsat image accuracy and landscape changes, a mixed methods approach was
used to collect and process the spatial data. Cimarron and Union Counties were investigated using a GPS
data collection of training samples for the purposes of an accuracy assessment and land cover change
analyses. Using that image, along with others, a land cover change analysis was performed to determine
how both Cimarron and Union Counties have changed between the years of 2001 and 2011.
Ground truthing is a process that allows a researcher to verify the classification results of a remotely
sensed image through the use of independent evidence (Hargrave 2006). A Trimble Juno 3B handheld GPS
unit was used to collect training samples in the field. Information collected on the GPS unit included the
researcher’s name, date, time, starting and ending points, latitude and longitude, and the training sample
classification and activity present at each location.
After the data was collected, the training sample points were used to run an accuracy assessment on
the 2011 National Land Cover Dataset. ESRI’s ArcGIS was utilized to compare the points with the
classified raster image. Using the ‘Extract Values to Points’ geoprocessing tool, we were able to compare
the classified points with the classified raster image. Simple statistics were performed on the points to
check for accuracy.
In order to conduct a land cover change analysis, the National Land Cover Datasets for 2001 and 2011
were clipped to our study areas. The raster calculator was used to identify areas of Shrubland,
Grassland/Herbaceous, and Cultivated Crops as well as areas where Grassland/Herbaceous changed to
Shrubland and Cultivated Crops.