The pyramid system for multiscale raster analysis

Cola, Lee De; Montagne, Nalan

doi:10.1016/0098-3004(93)90057-c

Cited by 8 publications

(5 citation statements)

References 14 publications

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“…The concept of the PM is similar to an image pyramid (e.g., Figure 14 (left)), which represents a raster image on multiple resolutions by aggregation and resampling. Image pyramids were originally developed in the areas of computer vision, image processing, and signal processing [26,27], and are widely used to enhance the efficiency of multi-scale raster rendering in GIS [28][29][30]. In our approach, the construction of a PM is similar to that of the TM in the sense of developing a hierarchy; but the PM represents space across scales instead of time.…”

Section: The Conceptmentioning

confidence: 99%

Re-Arranging Space, Time and Scales in GIS: Alternative Models for Multi-Scale Spatio-Temporal Modeling and Analyses

Qiang

Weghe

2019

IJGI

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The representations of space and time are fundamental issues in GIScience. In prevalent GIS and analytical systems, time is modeled as a linear stream of real numbers and space is represented as flat layers with timestamps. Despite their dominance in GIS and information visualization, these representations are inefficient for visualizing data with complex temporal and spatial extents and the variation of data at multiple temporal and spatial scales. This article presents alternative representations that incorporate the scale dimension into time and space. The article first reviews a series of work about the triangular model (TM), which is a multi-scale temporal model. Then, it introduces the pyramid model (PM), which is the extension of the TM for spatial data, and demonstrates the utility of the PM in visualizing multi-scale spatial patterns of land cover data. Finally, it discusses the potential of integrating the TM and the PM into a unified framework for multi-scale spatio-temporal modeling. This article systematically documents the models with alternative arrangements of space and time and their applications in analyzing different types of data. Additionally, this article aims to inspire the re-thinking of organizations of space, time, and scales in the future development of GIS and analytical tools to handle the increasing quantity and complexity of spatio-temporal data.

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Section: The Conceptmentioning

confidence: 99%

Re-Arranging Space, Time and Scales in GIS: Alternative Models for Multi-Scale Spatio-Temporal Modeling and Analyses

Qiang

Weghe

2019

IJGI

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“…Tile caches are based on a model called a tile pyramid, which subdivides a geographical region into a finite number of subregions using a set of l grids [6]. In Figure 1, a tile pyramid with three levels is shown.…”

Section: The Tile Pyramidmentioning

confidence: 99%

“…This offers an opportunity to replay the results of previous computations by placing geospatial results in a cache. A common approach to representing a set of geospatial results at multiple resolutions is to use a tiling scheme that divides a geographical data set into a hierarchical and finite set of tiles [6]. Unfortunately, the drawback of this approach is that the set of tiles is potentially very large [9], as the number of tiles is exponential in the number of supported resolutions.…”

Section: Introductionmentioning

confidence: 99%

TileHeat

Kefaloukos

Salles

Zachariasen

2012

Proceedings of the 20th International Conference on Advances in Geographic Information Systems

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Public geospatial services are now commonly available on the Web. These services often render maps to users by dividing the maps into tiles. Given that geospatial services experience significant user load, it is desirable to pre-compute tiles at a time of low load in order to increase overall performance. Based on our analysis of the request log of a public geospatial service provider, we observe that times of low load occur with a periodic pattern. In addition, our analysis shows that tile access patterns exhibit strong spatial skew.Based on these observations, we propose an adaptive strategy restricting the set of tiles that are pre-computed to fit the low load time window. Ideally, the restricted tile set should deliver performance comparable to the full tile set. To achieve this result, tiles should be selected based on their expected popularity. Our key observation is that the popularity of a tile can be estimated by analyzing the tiles that users have previously requested. Our adaptive strategy constructs heatmaps of previous requests and uses this information to decide which tiles to pre-compute. We examine two alternative heuristics, one of which exploits that nearby tiles have a high likelihood of having similar popularity. We evaluate our methods against a real production workload, and observe that the latter heuristic achieves a 25% increase in the hit ratio compared to current methods, without pre-computing a larger set of tiles.

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“…In the pyramid system (sometimes also used with quadtrees and various forms of image and video compression), cells in a high resolution raster image are generalized in square groups of four to create a lower‐resolution grid of the same image for display at smaller scales. This generalization occurs through a series of scales, creating a set of increasingly smaller grids that could be imagined as a “pyramid” if stacked on top of one another (De Cola and Montagne 1993).…”

Section: Web Map Optimization and The Adoption Of Server‐side Cachingmentioning

confidence: 99%

A Predictive Model for Frequently Viewed Tiles in a Web Map

Quinn

Gahegan

2010

Transactions in GIS

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Distributing pre-generated image tiles from a server-side cache is a fast and popular way of serving maps on the Web. However, these caches can grow unmanageably large for maps covering many scales over a broad extent. This research presents a model for determining high-priority geographic areas for tile caching. The model considers variables found in previous research to be of interest to Web map users, such as populated places, major roads, coastlines, and tourist attractions. The proportion of area, disk space, and time saved when creating a partial cache (consisting only of high-interest areas) and a cache of the entire map extent are compared to establish that marked savings are possible. Several applications of the model beyond tile caching are briefly discussed.

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The pyramid system for multiscale raster analysis

Cited by 8 publications

References 14 publications

Re-Arranging Space, Time and Scales in GIS: Alternative Models for Multi-Scale Spatio-Temporal Modeling and Analyses

Re-Arranging Space, Time and Scales in GIS: Alternative Models for Multi-Scale Spatio-Temporal Modeling and Analyses

TileHeat

A Predictive Model for Frequently Viewed Tiles in a Web Map

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