Day: January 26, 2010

Estimation of Stream Channel Geometry in Idaho Using GIS-derived Watershed Characteristics

/ Matt Artz

Environmental Modelling & Software, Volume 24, Issue 3, March 2009, Pages 444-448

Daniel P. Ames, Eric B. Rafn, Robert Van Kirk, and Benjamin Crosby

“This paper describes estimation of stream channel geometry with multiple regression analysis of GIS-derived watershed characteristics including drainage area, catchment-averaged precipitation, mean watershed slope, elevation, forest cover, percent area with slopes greater than 30 percent, and percent area with north-facing slopes greater than 30 percent. Results from this multivariate predictor method were compared to results from the traditional single-variable (drainage area) relationship for a sample of 98 unregulated and undiverted streams in Idaho. Root-mean-squared error (RMSE) was calculated for both multiple- and single-variable predictions for 100 independent, random subsamples of the dataset at each of four different subsample levels. The multiple-variable technique produced significantly lower RMSE for prediction of both stream width and depth when compared to the drainage area-only technique. In the best predictive equation, stream width depended positively on drainage area and mean watershed precipitation, and negatively on fraction of watershed consisting of north-facing slopes greater than 30%. Stream depth depended positively on drainage area and precipitation, and negatively on mean watershed elevation. Our results suggest that within a given physiographic province, multivariate analysis of readily available GIS-derived watershed variables can significantly improve estimates of stream width and depth for use in flow-routing software models.”

Mapping Whose Reality? Geographic Information Systems (GIS) and “Wild Science”

/ Matt Artz

Public Understanding of Science, Vol. 15, No. 4, 411-434 (2006)

Sally L. Duncan

“In taking the landscape-scale view increasingly demanded of natural resource management, scientific assessments make considerable use of geographic information systems (GIS) maps to convey the research findings they develop. Public interaction with scientists over natural resource management issues is therefore frequently mediated by such maps, which can directly influence how the landscape is viewed, and how science findings are communicated and understood. Analysis of the Coastal Landscape Analysis and Modeling Study (CLAMS) project in western Oregon reveals that GIS maps play a significant role in how we frame and address natural resource management issues. They can support the role of privileged knowledge as held by the map makers, typically scientists, and may reinforce it by the de facto “map tyranny” that gives primacy to scientific worldviews. But they can also enable broader kinds of inquiry through multiple frames of reference, enhancing story-making opportunities for stakeholders. Which of these trajectories is followed is affected by resource availability and new perceptions of responsibility, each of which reflects social power structures. The CLAMS case study suggests that map user/non-scientists appear less likely to be victims of “map tyranny” the more familiar they are with the technology. Accordingly, they become more likely to push for usable results from it, and more confident about engaging their own knowledge with that of the map maker/scientists.”

Research Associate/Senior Research Associate in Satellite Navigation Signal Processing and Receiver Design, University of New South Wales

/ Matt Artz / 1 Comment

POSITION 1: Research Associate/Senior Research Associate in GPS Interference Geolocation

The purpose of this role is to perform research and fulfill the School’s obligations under an ARC Linkage project “Locating Interference to GPS: Protecting the World’s Aircraft Landing Systems”. This project aims to design algorithms and equipment that can identify the location of interference using signal strength, Time-Difference-of-Arrival and Angle-of-Arrival techniques. The position reports to the Director of Research, Associate Professor Andrew Dempster who is the chief investigator for the project.

Main Duties:

  • design and run experiments requiring knowledge of GPS systems,
  • conduct field work,
  • design and evaluate effectiveness of algorithms,
  • collaborate with a large team of researchers and research students
  • liaise with the industrial partner, a local satellite systems integrator, and
  • write up results, to maximize the impact of the work through publications.

POSITION 2: Research Associate/Senior Research Associate in “System of Systems” Satellite Navigation Receiver Design

The purpose of this role is to fulfill the School’s obligations under an ARC Discovery project “Preparing for the next generation global navigation satellite system era: developing and testing user and reference station receiver designs”. This project aims to design algorithms and equipment that exploit all existing and proposed global navigation satellite system (GNSS) signals.

The position reports to the Head of School, Professor Chris Rizos, who is the chief investigator for the project.

Main Duties:

  • design and run experiments, requiring knowledge of GNSS,
  • conduct field work,
  • design and evaluate effectiveness of algorithms,
  • work with other researchers and research students,
  • liaise with other researchers working on sub-sets of the relevant signals,
  • write up results, to maximize the impact of the work through publications.

More information [PDF]

Crop Production and Road Connectivity in Sub-Saharan Africa: A Spatial Analysis

/ Matt Artz / 1 Comment

Africa Infrastructure Country Diagnostic (AICD) Working Paper 19

Paul Dorosh, Hyoung-Gun Wang, Liang You, and Emily Schmidt

February 2009

“This study adopts a cross-sectional spatial approach to examine the impact of transport infrastructure on agriculture in Sub-Saharan Africa using new data obtained from geographic information systems (GIS). Our approach involves descriptive statistical analysis and econometric regressions of crop production or choice of technology for each location (a 9×9 kilometer pixel) in Sub-Saharan Africa on (a) agroecological zones and crop production potentials by the Food and Agriculture Organization (FAO) and the International Institute for Applied Systems Analysis (IIASA), (b) GIS data on crop production from the International Food Policy Research Institute’s (IFPRI) spatial crop allocation model (SPAM), and (c) road infrastructure based largely on data from the United Nations Environment Programme (UNEP) and estimated travel times.

“We address three main issues. First, we analyze the impact of road connectivity on crop production and choice of technology when we control basic supply and demand factors. Second, we investigate the impact on agricultural output of investments that reduce travel time on roads of various types. Third, we provide an example of how this type of analysis could be used to construct benefit-cost ratios of alternative road investments in terms of enhanced agricultural output per dollar invested.

“We find that agricultural production and proximity (as measured by travel time) to urban markets are highly correlated, even after taking agroecology into account. Likewise, adoption of highproductive/ high-input technology is negatively correlated with travel time to urban centers.

“There is substantial scope for increasing agricultural production in Sub-Saharan Africa, particularly in more remote areas. Total crop production relative to potential production is 45 percent for areas within four hours’ travel time from a city of 100,000 people. In contrast, it is just 5 percent for areas more than eight hours away. These differences in actual versus potential production reflect the relatively small share of land cultivated out of total arable land in more remote areas.

“For remote regions, low population densities and long travel times to urban centers sharply constrain production. Reducing transport costs (travel time) to these areas would expand the feasible market size for these regions, easing the constraint on production. If the expansion in production from these areas were small in terms of the relevant regional, national, or subnational market, average market prices outside the formerly remote region would be unaffected, and significant aggregate production increases could result.

“We find some interesting differences between East Africa and West Africa. On average, East Africa has lower population density, smaller local markets, and lower road connectivity—the average travel time to the nearest city is more than twice that in West Africa. While average suitable area for crop production is similar in East and West Africa, average crop production per pixel in East Africa is just 30 percent of that in West Africa. Road connectivity has different impacts in the two regions. In East Africa the results are similar as for all Sub-Saharan Africa. Longer travel time decreases total crop production, and reducing travel time significantly increases adoption of high-input/high-yield technology in East Africa, but the impacts are insignificant for West Africa. This may be because the more densely roads are connected, the smaller the marginal benefits of more connections. West Africa already has a relatively well-connected road network.”

Krigging as a Tool for Interpreting Structural Data: Exploring Spatial Analysis of Complex Folding on Seguin Island, Maine

/ Matt Artz / 1 Comment

Geological Society of America, Northeastern Section (45th Annual) and Southeastern Section (59th Annual) Joint Meeting (13-16 March 2010)

BABCOCK, Lori N., LIPIEC, Eva, BAMPTON, Matthew, and SWANSON, Mark T.

“Seguin Island, located ~12 km SSW of Georgetown, Maine and SE of the Norumbega fault zone consists of Devonian upright F2 anticlines and synclines, with complex parasitic fold structures. Ordovician Cape Elizabeth amphibolite gneiss and syntectonic granite dikes are exposed over the entire coast of the island. Structural data was collected in the NE zone of the western lobe where the folds are best exposed to assess the results of the spatial analysis of collected field data. Orientations of gneissic layering, axial planes, and fold axes were taken with a Brunton compass and recorded with handheld GPS. Gneissic layer lines were traced 2-3 m apart using RTK GPS and Total Stations to delineate the exact fold geometry, and interpreted extensions were digitized in the lab. The fold structures were found to be tight, SW-plunging with NNE striking axial planes, a wavelength of ~10m and amplitude of ~5m but can be highly variable with smaller scale parasitic folds abundant. Kriging, a spatial analysis technique that interpolates values between measured points was used to analyze the structural data. The results of kriging are based on a selected density of data points, or kernel, which best represents the entire set. Effective selection of these points requires knowledge of variations in the dataset. Strike and trend structural measurements were normalized to an 180o scale and divided into nine classes to best display the data. After kriging, the data was converted into a histogram with breaks that were manually shifted to reclassify the data. These breaks were adjusted to better represent the variance of data from the mode in each set. Strong correlations were found in the strike of gneissic layers, and axial planes, and the trend of fold axes. Strike of gneissic layers alternated NNE to NE orientations, suggesting differences in limb orientation across anticline and syncline fold axes. All dip and plunge measurements also became less steep from N to S, clearly visible in the kriging results. Kriging produced interpolated results that clearly reflected the structure of the local area, providing a useful means of visualization. Kriging can provide valuable insight into prevailing structural patterns, correlating features across a given area, and results in a representation of geologic data that is interpretable on an entirely new level.”