GOOD NEWS: PARTITIONING A SIMPLE POLYGON BY COMPASS DIRECTIONS

Motivated by geographic information retrieval, we study the problem of partitioning a simple polygon into four parts that can be considered as the North, East, West, and South. We list criteria for such partitionings, propose formalizations into geometric problems, and give efficient algorithms. An implementation and tests on country outlines show the results for three different partitionings.

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A Low frequency Southern Sky Survey Using the Mauritius Radio Telescope

Symposium - International Astronomical Union ◽

10.1017/s0074180900168494 ◽

2002 ◽

Vol 199 ◽

pp. 25-31

Author(s):

N. Udaya Shankar

Keyword(s):

Radio Telescope ◽

Low Frequency ◽

Fourier Synthesis ◽

North East ◽

The North ◽

Sky Survey ◽

Correlation Receiver ◽

Complex Correlation ◽

Right Ascension ◽

East West

The Mauritius Radio Telescope (MRT) is a Fourier synthesis instrument which has been built to fill the gap in the availability of deep sky surveys at low radio frequencies in the southern hemisphere. It is situated in the north-east of Mauritius at a southern latitude of 20°.14 and an eastern longitude of 57°.73. The aim of the survey with the MRT is to contribute to the database of southern sky sources in the declination range −70° ≤ δ ≤ −10°, covering the entire 24 hours of right ascension, with a resolution of 4' × 4'.6sec(δ + 20.14°) and a point source sensitivity of 200 mJy (3σ level) at 151.5 MHz.MRT is a T-shaped non-coplanar array consisting of a 2048 m long East-West arm and a 880 m long South arm. In the East-West arm 1024 fixed helices are arranged in 32 groups and in the South arm 16 trolleys, with four helices on each, which move on a rail are used. A 512 channel, 2-bit 3-level complex correlation receiver is used to measure the visibility function. At least 60 days of observing are required for obtaining the visibilities up to the 880 m spacing. The calibrated visibilities are transformed taking care of the non-coplanarity of the array to produce an image of the area of the sky under observation.This paper will describe the telescope, the observations carried out so far, a few interesting aspects of imaging with this non-coplanar array and present results of a low resolution survey (13' × 18') covering roughly 12 hours of right ascension, and also present an image with a resolution of 4' × 4'.6sec(δ + 20.14°) made using the telescope.

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The mineralogical composition of some Scottish soils

The Journal of Agricultural Science ◽

10.1017/s0021859600006717 ◽

1925 ◽

Vol 15 (3) ◽

pp. 257-271 ◽

Cited By ~ 11

Author(s):

James Hendrick ◽

George Newlands

Keyword(s):

Mineralogical Composition ◽

Fine Sand ◽

Plant Food ◽

Sand Fraction ◽

Extensive Survey ◽

North East ◽

The North ◽

Local Origin ◽

East West ◽

Made In

1. Previous investigations showed that certain Scottish soils were of glacial drift origin, that they were comparatively rich in unweathered silicates and therefore in reserves of plant-food, that they showed considerable variation in such silicates and were capable of classification accordingly. Some indication was also shown that the glacial drift, and hence the resulting soil, was sometimes of local origin, its character being determined by the underlying rock. In the present investigation a more extensive survey of Scottish soils has been made in order to discover to what extent these preliminary findings might be applicable generally.2. For this purpose soils have been collected from various localities in the north, north-east, west and south of Scotland, and have been analysed mechanically and the “fine sand” fraction examined mineralogically.

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Concept-aware geographic information retrieval

Proceedings of the International Conference on Web Intelligence - WI '17 ◽

10.1145/3106426.3106498 ◽

2017 ◽

Cited By ~ 2

Author(s):

Noemi Mauro ◽

Liliana Ardissono ◽

Adriano Savoca

Keyword(s):

Information Retrieval ◽

Geographic Information ◽

Geographic Information Retrieval

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Geographic Information Retrieval and the World Wide Web: A Match Made in Electronic Space

Cartographic Perspectives ◽

10.14714/cp26.717 ◽

1997 ◽

pp. 13-26 ◽

Cited By ~ 2

Author(s):

David Johnson ◽

Myke Gluck

Keyword(s):

Information Retrieval ◽

World Wide Web ◽

Information Needs ◽

World Wide ◽

Data Retrieval ◽

Query Languages ◽

Geographic Information ◽

Geographic Information Retrieval ◽

Retrieval Systems ◽

The World

This article looks at the access to geographic information through a review of information science theory and its application to the WWW. The two most common retrieval systems are information and data retrieval. A retrieval system has seven elements: retrieval models, indexing, match and retrieval, relevance, order, query languages and query specification. The goal of information retrieval is to match the user's needs to the information that is in the system. Retrieval of geographic information is a combination of both information and data retrieval. Aids to effective retrieval of geographic information are: query languages that employ icons and natural language, automatic indexing of geographic information, and standardization of geographic information. One area that has seen an explosion of geographic information retrieval systems (GIR's) is the World Wide Web (WWW). The final section of this article discusses how seven WWW GIR's solve the the problem of matching the user's information needs to the information in the system.

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