Accuracy Assessment of NLCD 2011 percent impervious cover for selected USA Metropolitan Areas.

The emergence of high-resolution land cover data has created the opportunity to assess the accuracy of impervious cover (IC) provided by the National Land Cover Database (NLCD). We assessed the accuracy of the 900 m2 NLCD2011 %IC for 18 metropolitan areas throughout the conterminous United States using reference data from 1 m2 land cover data developed as part of the United States Environmental Protection Agency's EnviroAtlas project. Agreement was assessed from two perspectives: 1) sensitivity to the size of the assessment unit used for the comparison, and 2) utility of NLCD %IC to serve as a proxy for high-resolution IC. The former perspective was considered because statistical relationships can be sensitive to assessment unit size and shape, and the latter perspective was considered because high resolution (reference) %IC data are not available nationwide. The utility of NLCD %IC as a proxy for the high resolution data was assessed for seven lattice (square) cell sizes ranging from 1 ha to 200 ha using four EnviroAtlas IC indicators: 1) %IC per 100 ha (1 km2); 2) %IC by Census block group; 3) %IC within a 15 m (radius) of the riparian zone, and; 4) %IC within a 50 m (radius) of the riparian zone. Agreement was quantified as per assessment unit deviation (NLCD %IC - reference %IC) and summarized as Mean Absolute Deviation (MAD) and Mean Deviation (MD) both within and across the 18 metropolitan areas. Ordinary least squares (OLS) regression (y = reference %IC and x = NLCD %IC) was also used to evaluate the quality of the NLCD %IC data. MAD was ≤ 5% for six of the seven lattice cell sizes. MAD was also ≤ 5% for Census block groups > 100 ha and for both riparian units. These results suggest that uncertainty attributable to the measurement of %IC was no greater than the uncertainty related to the effect of IC on aquatic resources that have been derived from studies of aquatic condition (e.g., benthic fauna) over a range of %IC. Overall, agreement was variable from one metropolitan area to the next. Agreement improved as assessment unit size increased and declined as the level of urbanization (NLCD %IC) increased. NLCD %IC tended to underestimate reference %IC overall, but NLCD %IC was sometimes greater than reference %IC in urbanized settings.

Influence of high-resolution data on the assessment of forest fragmentation.

CONTEXT: Remote sensing has been a foundation of landscape ecology. The spatial resolution (pixel size) of remotely sensed land cover products has improved since the introduction of landscape ecology in the United States. Because patterns depend on spatial resolution, emerging improvements in the spatial resolution of land cover may lead to new insights about the scaling of landscape patterns. OBJECTIVE: We compared forest fragmentation measures derived from very high resolution (1 m2) data with the same measures derived from the commonly used (30 m × -30 m; 900 m2) Landsat-based data. METHODS: We applied area-density scaling to binary (forest; non-forest) maps for both sources to derive source-specific estimates of dominant (density ≥ 60%), interior (≥ 90%), and intact (100%) forest. RESULTS: Switching from low- to high-resolution data produced statistical and geographic shifts in forest spatial patterns. Forest and non-forest features that were "invisible" at low resolution but identifiable at high resolution resulted in higher estimates of dominant and interior forest but lower estimates of intact forest from the high-resolution source. Overall, the high-resolution data detected more forest that was more contagiously distributed even at larger spatial scales. CONCLUSION: We anticipate that improvements in the spatial resolution of remotely sensed land cover products will advance landscape ecology through reinterpretations of patterns and scaling, by fostering new landscape pattern measurements, and by testing new spatial pattern-ecological process hypotheses.

Accuracy assessment of NLCD 2011 impervious cover data for the Chesapeake Bay region, USA.

The National Land Cover Database (NLCD) contains three eras (2001, 2006, 2011) of percentage urban impervious cover (%IC) at the native pixel size (30 m-×-30 m) of the Landsat Thematic Mapper satellite. These data are potentially valuable to environmental managers and stakeholders because of the utility of %IC as an indicator of watershed and aquatic condition, but lack an accuracy assessment because of the absence of suitable reference data. Recently developed 1 m2 land cover data for the Chesapeake Bay region makes it possible to assess NLCD %IC accuracy for a 262,000 km2 region based on a census rather than a sample of reference data. We report agreement between the two %IC datasets for watersheds and the riparian zones within watersheds and four additional square units. The areas of the six assessment units were 40 ha cell, 433 ha (riparian mean), 2756 ha cell, 5626 ha cell, 8569 ha (watershed mean) and 22,500 ha cell. Mean Absolute Deviation (MAD) and Mean Deviation (MD) were about 1.5% and -1.5%, respectively, for each of the assessment units except for the riparian unit, for which MAD and MD were 0.88 and 0.62, respectively. NLCD reliably reproduced %IC from the 1 m2 data with a small, consistent tendency for underestimation. Results were sensitive to assessment unit choice. The results for the four largest assessment units had very similar regression parameters, R2 values, and bias patterns. Results for the riparian assessment were different from those for the watershed unit and the other three larger units. MAD was about 50% less for the riparian zones than it was for the watersheds, the direction of bias was less consistent, and NLCD %IC was uniformly higher than 1 m2 %IC in urbanized riparian zones. For the smallest unit, bias patterns were more similar to the riparian unit and regression results were more similar to the four larger units. MAD and MD were also sensitive to the amount of urbanization, increasing as NLCD %IC increased. The low overall bias and positive relationship between bias and urbanization suggest that the benefits of obtaining 1 m2 IC data outside of urban areas may not outweigh the costs of obtaining such data.

An introduction to minimally invasive therapy.

Minimally invasive therapy (MIT) has as its basic premise the reduction of iatrogenic trauma to the patient by surgeon, physician or radiologist. This approach must also imply that the therapeutic procedure succeeds in its aim of cure in a manner no less effective than is currently achievable by established methods of treatment. Acceptance of this principal has many identifiable sequelae, including profound changes in hospital design, increasingly expensive technological instrumentation, more sophisticated teaching and learning patterns, and a massive redirection of health care financial resources. These changes cannot be contemplated at leisure, because they are dynamically imperative and progressing with relentless rapidity, being directly driven by the consumer. It is vital that this shift in clinical emphasis should be appreciated so that future planning can be undertaken with some rationality.

Percutaneous cholecystolithotomy: the first 60 patients.

OBJECTIVE: To assess the feasibility and possible complications of percutaneous removal of gall stones. DESIGN: Prospective study of the first 60 patients treated. SETTING: The London Clinic. PATIENTS: 60 Consecutive patients with symptomatic gall stones who agreed to have them removed percutaneously. RESULTS: 56 Patients had stones successfully removed percutaneously. In four patients failure of access necessitated a cholecystectomy under the same anaesthetic. Two patients had an empyema of the gall bladder drained initially, followed by a second operation to remove the stones one week later. Seven patients had postoperative complications, and two had recurrences of biliary calculi. CONCLUSIONS: The techniques and instruments used in percutaneous nephrolithotomy can successfully be adapted for percutaneous removal of gall stones. The procedure is suitable for a wider range of patients than other techniques that leave the gall bladder intact.

Tethered ureteric stents--a clinical assessment.

The acceptability and complications of tethered double-J stents were assessed in 17 patients. The study showed tethered ureteric stents to be safe, well tolerated and easy to remove. The technique avoids unnecessary ureteral instrumentation and general anaesthesia and has benefits for both patients and hospital resources.

Ureterorenal endoscopy: which instrument, what cost?

This report describes the design, availability, repair facilities and costs of rigid ureteroscopes. Clinical factors affecting design are detailed. A classification is given. A new test of flow dynamics is described. Short operating ureteroscopes with a stable or integral telescope system appear to be superior to other types, especially as they may be used for antegrade ureteroscopy.

Comparison of treatment of renal calculi by open surgery, percutaneous nephrolithotomy, and extracorporeal shockwave lithotripsy.

This study was designed to compare different methods of treating renal calculi in order to establish which was the most cost effective and successful. Of 1052 patients with renal calculi, 350 underwent open surgery, 350 percutaneous nephrolithotomy, 328 extracorporeal shockwave lithotripsy (ESWL), and 24 both percutaneous nephrolithotomy and ESWL. Treatment was defined as successful if stones were eliminated or reduced to less than 2 mm after three months. Success was achieved in 273 (78%) patients after open surgery, 289 (83%) after percutaneous nephrolithotomy, 301 (92%) after ESWL, and 15 (62%) after percutaneous nephrolithotomy and ESWL. Comparative total costs to the NHS were estimated as 3500 pounds for open surgery, 1861 pounds for percutaneous nephrolithotomy, 1789 pounds for ESWL, and 3210 pounds for both ESWL and nephrolithotomy. ESWL caused no blood loss and little morbidity and is the cheapest and quickest way of returning patients to normal life.

A preliminary in vivo assessment of acrylic acid graft-copolymers in the urinary tract.

Polymers such as polyethylene, polytetrafluorethylene and polypropylene may be copolymerized with acrylic acid by radiation initiation to produce copolymers which are cationic hydrogels and thus possess physical properties different to the base polymers from which they are derived. The present preliminary study was undertaken to determine whether this class of material may have potential application for use within the urinary tract. Inserts of such copolymers in sheet form (5 mm. square) and their corresponding base polymers were placed in the bladders of male Wistar rats as free floating grafts and left in situ for 3 months. Stone formation and/or encrustation occurred on 12 of the 16 radiation graft copolymers and on 9 of 11 of the corresponding base polymers. The altered physical properties of the tested acrylic acid graft copolymers appear to offer no additional resistance to encrustation although their plasticity and ability to swell in water may provide some advantages over more conventional polymeric materials.

Percutaneous nephroscopy: a review of the physical properties, suitability and cost of the instruments.

The physical properties, suitability and cost of six instruments used for elective percutaneous renal endoscopy have been evaluated. Three were rigid and three were flexible. The optics, flow rate and accessories of the rigid instruments have been demonstrated to be superior to the flexible instruments. Flexible instruments, however, were used in 15% of our 70 elective percutaneous operations. The 21-Charr cystoscope was adequate for extracting smaller calculi, but it was necessary to use the Storz and Wolf rigid nephroscopes when ultrasonic disruption was required. Based on our data, improvements and modifications to both flexible and rigid instrument design are suggested.

The obstructed kidney: correlation between renal function and urodynamic assessment.

In 20 patients with pelvi-ureteric junction obstruction the results of quantification of the change in renal pelvis size during high-dose intravenous urography with a diuretic, pressure/flow studies, standard renography and deconvolution analysis of the gamma camera renogram have been compared. The results of high-dose intravenous urography and pressure/flow studies correlated well. Renography was unreliable in diagnosing obstruction unless deconvolution analysis of the gamma camera renogram was used to differentiate those showing an obstructive uropathy from those with an obstructing nephropathy.

A computer-based record and organisation system for a department of urology.

This paper describes the development and practical application of a computer-based record system in a urological department. It demonstrates how such a system can provide a clinical flow sheet for day-to-day use combined with a computerised data store for both clinical evaluation and for research purposes. The paper also outlines how the system has improved patient handling and general departmental efficiency.