Showing papers on "Occupancy published in 1997"

Improved Occupancy Grids for Map Building

Abstract: Occupancy grids are a probabilistic method for fusing multiple sensor readings into surface maps of the environment. Although the underlying theory has been understood for many years, the intricacies of applying it to realtime sensor interpretation have been neglected. This paper analyzes how refined sensor models (including specularity models) and assumptions about independence are crucial issues for occupancy grid interpretation. Using this analysis, the MURIEL method for occupancy grid update is developed. Experiments show how it can dramatically improve the fidelity of occupancy grid map-making in specular and realtime environments.

Patch occupancy in Coenonympha tullia (Muller, 1764) (Lepidoptera: Satyrinae): habitat quality matters as much as patch size and isolation

Abstract: Patch occupancy by Coenonympha tullia has been surveyed in 166 sites in Northumberland, UK It was found in 117 of them and absent in 37 Weather conditions were too poor to determine its presence at a further 12 sites Differences in habitat quality among sites account for patch occupancy as successfully (R2 = 48%) as isolation and patch size jointly (R2 = 46%) This finding has relevance for metapopulation studies as it demonstrates that greater attention should be given to differences in habitat quality among patches beyond their size and distance from one another Together, habitat quality, patch size and isolation account for 61% of the variation in C tullia occupancy of sites and discriminant analysis produces a correct classification for > 88% of sites Habitat quality and patch size jointly account for much the same variance, and result in the same classification of the twelve sites excluded from analysis, as they do in conjunction with patch isolation This result suggests that there is potential for predicting changes in occupancy of sites from site specific data in the face of changes to biotopes, such as planned exploitation and deterioration of sites from other causes including climate change and management practices

Shelters for runaway and homeless youths: Capacity and occupancy

Abstract: Data from a nationally representative sample of shelters for runaway and homeless youths (N = 160) were analyzed to determine shelter capacity, occupancy, and occupancy ratios. Analysis focused in particular on occupancy ratios by funding status, shelter size, metropolitan statistical area (MSA), season, and day of the week.

Interspecific abundance-occupancy relationships : a test of mechanisms using microcosms

Abstract: 1. Several hypotheses have been proposed to account for the widely observed positive interspecific relationship between the local abundance and number of sites occupied. Here we provide a test of some of these hypotheses using data from microcosm communities of protists, in which sets of individual communities are linked by varying rates of dispersal. 2. Positive relationships between abundance and occupancy were found over all the dispersal rate treatments, including those with no between-community dispersal. 3. Species tended to be consistent in their position in the abundance-occupancy relationship, both within and between treatments. 4. The design of the experiment makes it unlikely that (i) sampling artefacts, (ii) geographical range position, (iii) niche breadth, (iv) resource availability, or (v) vital rates mechanisms are appropriate, or sole explanations for the observed patterns, though biotic heterogeneity complicates the interpretation of (ii)-(v). 5. The results fail to support the specific hypotheses based on metapopulation dynamics, but suggest that occupancy may be driven by local abundance, combined with a very general (not specifically metapopulation-structured) set of extinction and colonization processes.

Traditional land use and occupancy studies and their impact on forest planning and management in Alberta

Abstract: Canada is an international leader in the methodology of traditional land use and occupancy mapping as a result of the negotiation process for settling comprehensive land claims in the North. Since the early 1980s this methodology has found increasing application in the Canadian mid-North, especially in the context of forest planning and management in the northern Alberta Forest Management Agreement (FMA) areas. The goals of traditional land use and occupancy mapping in these FMAs include collection and preservation of traditional environmental knowledge, integration of this knowledge into forest planning and management and, for the Aboriginal communities, active participation in decision-making processes in order to attain sustainable forest management. While the first goal is often met in mapping projects, goals two and three are proving harder to achieve because of conflicting government policy agendas, differing paradigms of community development in society at large, and the lack of recognition and leg...

Security Measures and the Apartment Market

Abstract: This study examines the effect of security measures on apartment rent and occupancy. Three variables representing various security measures are estimated in a simultaneous model of rent and occupan...

Improved vehicle occupancy data collection methods

Abstract: This report evaluated current and emerging vehicle occupancy data collection methodologies. Five primary methods for collecting vehicle occupancy data were identified: the traditional roadside/windshield observation method, a recently developed carousel observational method, photographic surveillance, mail-out or telephone surveys, and accident database extraction method. The findings show that other methods besides the traditional windshield method may be advantageous for collecting vehicle occupancy information. The key factors in selecting a collection method are the conditions under which vehicle occupancy is to be estimated. For example, the accident method and mail-out surveys are well suited for developing regional vehicle occupancy estimates, while the windshield method and carousel method are well suited for corridor-specific estimates. Another key finding, which impacts the selection of a method and sampling period, is the fact that average vehicle occupancy (AVO) estimates vary significantly by time-of-day, day-of-week, and month-of-year. The implication of this finding is that agencies cannot continue to infer yearly AVO estimates from data collected during a limited time period such as the morning rush hour period. Recommendations for selecting and implementing a vehicle occupancy data collection method are also provided.

Occupancy rates and habitat relationships of northern goshawks in historic nesting areas in Oregon

Abstract: approval: Stephen De Stefano The ability of northern goshawks (Accipiter gentilis) to persist in intensively managed and selectively harvested forest habitats is largely unknown. To address the concern that populations of northern goshawks in eastern Oregon may be declining in response to habitat alteration, I studied occupancy rates and habitat relationships of nesting goshawks on the Fremont National Forest and adjacent private lands during 1992-1994. My objectives were to determine if historic territories (i.e., those occupied season during 1973-1991) were still occupied, document current site conditions and quantify changes in forest cover on those territories between 1973-1994, and compare present conditions of forest vegetation between nest sites that were currently occupied and those where I did not detect the presence of territorial goshawks (no-response sites). In 1994, I surveyed a forest-wide random sample of 51 historic nest sites, stratified by forest cover type. Occupancy of historic sites by goshawks was 29% (15 of 51), compared to 79% (30 of 38) mean annual occupancy rate of current territories (found initially during 1992-1994). Across all strata, 86% of current nest sites (n = 38) were in Mid-aged or Late structural stage forest (trees >23 cm DBH) with >50% canopy closure. Among the historic territories used for analysis (n = 46), those found occupied Redacted for Privacy (n = 15) in 1994 had significantly more Mid-aged Closed forest (average stand DBH 23­ 53 cm, <15 trees per ha >53 cm DBH; >50% canopy closure) and Late Closed forest (15 trees per ha >53 cm DBH; >50% canopy closure) than no-response sites (n = 31). This relationship was significant (P < 0.05) for circular scales of 12, 24, 52, 120, and 170 ha surrounding goshawk territory centers. Within the 52 ha scale around historic nest sites surveyed in 1994, occupied sites had 49% (SE = 6.6) total Late Closed and Midaged Closed forest, while sites with no response had 19% (SE = 3.0) total Late and Midaged Closed forest. Historic sites had 51% (SE = 3.8) total Late and Mid-aged Closed forest when last known occupied before 1992. Among historic territories, mean percent area of habitat in Late Closed forest at the 12 ha nest stand scale was 4 times greater in occupied (27%) than in no-response sites (6%) (P < 0.05). A logistic regression model for occupied sites confirmed the importance of Late Closed and Mid-aged Closed forests as indicators of quality habitat within the 52 ha scale on historic sites where goshawks were still present in 1994. Goshawk pairs were more likely to persist in historic territories having a high percentage of mature and older forest (about 50%) in closed-canopied conditions within the 52 ha scale, suggesting that little or no habitat alteration within aggregate nest stands is important to ensure the persistence of nesting pairs. I recommend preserving multiple nest stands within the 52 ha scale and discourage further cutting of large, late and old structure trees (>53 cm DBH) within the PFA to preserve stand integrity, maintain closed canopies, maintain connectivity to alternate nest stands, and optimize conditions for breeding goshawk pairs to persist. Occupancy Rates and Habitat Relationships of Northern Goshawks in Historic Nesting Areas in Oregon

Means of escape in case of fire ‐ a flexible approach

Abstract: Considers aspects of the requirements of the current building regulations as they relate to fire design and fire safety. Reviews the requirements of Part B in respect of occupancy and travel distances. States that research would suggest that a designer may be required to provide additional escape facilities in one part of the country and not in another and that research would suggest that scope for flexibility is significant.