Konsep Dasar pada GIS

Seperti biasa, mempelajari hal-hal baru pasti dihadang dengan konsep-konsep maupun istilah-istilah yang harus dimengerti agar bias mempelajari hal-hal yang lebih dalam lagi. Berikut ini beberapa hal yang mungkin dibutuhkan oleh siswa yang sedang belajar GIS. Sebelumnya kita definisikan dulu GIS sebagai sistem informasi yang bekerja dengan data dengan referensi spatial atau koordinat geografis. Bisa juga diartikan sistem basis data dengan kemampuan khusus dalam menangani data dengan referensi spatial layaknya beroperasi dengan data biasa. Dengan kata lain, data yang diolah adalah data tentang lokasi, biasanya koordinat. Spatial objects adalah area geografis dengan atribut beserta karakteristiknya.

1. Apa bedanya map, aerial photo, dan satellite imagery?

Map is geographic features or spatial information presented graphically. It conveys information about location and its attribute. Position of particular geographic feature on earth is 2D and 3D. Map contain point, line and area features. Also there are attribute information such as feature types, name, number of code, area/length, and other quantitative information. Aerial photo is taking of photograph of the ground from camera with elevation using fixed-wing aircraft, helicopters, multi-rotor unmanned aircraft system (UAS), balloons, blimps and dirigibles, rockets, kites, parachutes, stand-alone telescoping mounting on vehicles. Those photograph maybe with photographer or automatically shoot. Satellite imagery is similar to aerial photo but using satellite to capture an image. There are four type of resolution: spatial, spectral, temporal, and radiometric. This images have many applications in meteorology, oceanography, fishing, agriculture, biodiversity conservation, forestry, landscape, geology, regional planning, education, intelligence, and warfare. In 1972, US start a landsat program that capture image from space.

2. Jelaskan konsep data geospatial.

Geospatial data is data related to geographic location and its characteristics of natural or constructed features and boundaries on earth.

3. Sebutkan lima jenis peta dan penggunaannya.

Jenis peta sangat banyak, jenis pertama adalah: 1). Climate maps. Give general information about the climate and precipitation (rain and snow) of a region. Biasanya menggunakan warna untuk memetakan zona-zona nya. 2). Economic or Resources Map. Feature the major types of natural resources or economic activity in an area. Cartographers use symbol to show the location of natural resources or economic activities. For example, wheat on an area, paddy, etc. 3). Physical map. Illustrate a physical area such as mountains, rivers, and lakes. The water is usually shown in blue. Green for lower elevation, orange and brown for higher elevation. 4). Political Map. It show state and national boundaries and capital and major cities. A Capital city is usually marked with a start within circle. 5). Street Map / Road Map. Illustrate smaller area as towns and cities. People use it to find direction to a place where to go. 6). Topographic Map. Include contour to shows elevation of an area. Line near show steep terrain, and line far away show flat terrain. It useful for hiking, and geologist to record the type of rock.

4. What is Map Resolution and Image Resolution?

Resolution is distinguishing individual parts. Spatial resolution for geographic data as the content of the geometric domain divided by the number of observations, normalized by spatioal dimension. Map resolution is term to know how accurately the location and shape of map features can be depicted for a given map scale. Therefore, in larger scale maps, features more closely matches real world features. Image Resolution is detail an image holds. Applies to raster digital images. Basically resolution quantifies how close lines can be to each other and still be visible resolved.

5. Discuss about Ideal GIS, Accuracy standards for maps (U.S), factors affecting map accuracy, and what is map extent and database extent.

Ideal GIS is GIS that accommodate open data policy, interoperable procedure, multidisciplinary, networking, data/information sharing, and standardization. Accuracy standard for maps in USA is announced in 1947 said that for maps scale larger than 1:20,000 no more than 10% of features shall be more than 1/30th of an inch from their intended location on maps. For scale smaller than 1:20,000 said no more than 10% of features shall be more than 1/50th of an inch from their intended location. Factor affecting accuracy are: map resolution, quality of source data, map scale, drafting skill, width of line used to depict features. A map extent is a portion of area of a region shown in map. The limits of map extent are defined in coordinate system of the map. In western culture, map extents usually have a rectangular shape, so they are defined with a minimum and maximum width and height. In dynamic map can be accessed by zooming and panning.

6. What are logical operators available in arcview GIS? Discuss about them.

There is Boolean logical operator: AND, OR, and NOT. Also there are other logical such as >, >=, <, <= and <>. It appears like calculator when we query some spatial data.

7. Explain the essential element of a layout of the map. The basic elements of maps: title, legend, names of features, directional indicator, scale and map grid.

8. Explain 4 M in GIS? 4 M in GIS are Model (modeling and simulation), Map (creating a map), Measure (finding a distance, etc), and Monitor (seeing realtime).

9. Discuss importance of remote sensing in GIS. Remote sensing is collecting and interpreting information about the environment and the surface of the earth from distance, primarily by sensing radiation that is naturally emitted or reflected by the earth surface from the atmosphere, or by sensing signals transmitted from a device and reflected back to it. The methods are photography, radar, and satellite.

10. What are the functional elements of GIS? Explain. GIS functional elements are Data acquisition, data preprocessing, data management, data manipulation & analysis, and data product generation. Data acquisition is process of identifying and gathering the data required for the app. Data preprocessing is manipulating data in several ways to be able to prepare it for further modeling. It also covertion format, georeferencing (geometric correction and resampling), and also establishing a consistent system for recording. Data management is for helping in creating and assessing the database with consistent method for data entry, update, delete and retrieve. Data manipulation and analysis is working within database to derive new information using statistical tool, modeling, logical and Boolean tools, and specialized model. Product generation is soft copy and hard copy style and also cartographic principles built-in computer aided drafting tool. Product presentation maybe report (table, map, write-up) or multimedia.

11. Explain the difference between topology and topography. In geodatabases, topology is the arrangement that constrains how point, line, and polygon features share geometry. In Arcview topology is spatial relationship between connecting or adjacent features in geographic data layer. Topography merupakan representasi dari bentuk permukaan (surface shape and features of the earth and maybe other planets. Including relief and the position of natural and constructed features.

12. What is the table join? Table join is merging two or more tables based on a field. These tables have a join field as connector for other fields and these tables become one merging tables that share other attribute.

13. What is attribute aggregation? The process of collecting a set of similar, usually adjacent, polygon (with their associated attribute) to form a single, larger entity.

14. What is address matching? A process that compares an address or a table of addresses to the address attributes of a reference dataset to determine whether a particular address falls within an address range associated with a feature in the reference dataset. If an address falls within a feature’s address range, it is considered a match and a location can be returned.

15. Explain the centroid, buffer operation, map overlay (raster and vector) and cutting and filling operation. Centroid is average location of a line or polygon, also center of mass of a two or three dimensional object. Overlay is techniques involve the compositioning or extracting multiple maps t create a new dataset. Cutting and filling operation to create a volume or area that cut or fill with some capacity.

Untuk istilah yang lain dapat dicari lewat searching di ESRI.

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