GIS in Windows

QGIS

QGIS is one of GIS software with open source licensing under the GNU General Public License (GPL). That means that the source code used in building applications can we learn and change, and we can get for free. Unlike with commercial software in general, where the source code is closed so that the user can not develop their own application in accordance morning. QGIS is an abbreviation of Quantum Geographic Information System. GIS software is made starting in May 2002 and has been defined as projects in the SourceForge in June 2002. One of the advantages of this software QGIS is a lightweight and user-friendly. QGIS also has some version suitable with the platform, so it can run on Windows, Linux, and OSX. QGIS built using Qt and C + +. Early goal from making QGIS only as a viewer data only, but added with a growing variety of other plugin that works as a database management, spatial analysis, or to attach the display, so now QGIS not powerfull compared to other software such as ArcView GIS, or GRASS.

In addition QGIS still many other GIS software that can compete with commercial GIS software, which is currently dominated by ESRI. Open Source Applications (OS) SIG itself can be categorized into 2, namely the Library SIG OS and application OS SIG. Library GDAL such as GIS, the OS / ORG, Proj4, GEOS, GML4J, JTS, GeoTools, created with the goal of building a module in the application. GIS applications OS preferable to the interests of users in the GIS process. OS GIS applications can be divided into 3 types:

1) Desktop Applications. Such as: QGIS, GRASS, MapWindow, Thuban, OpenMap, ILWIS, etc..
2) Web-based applications. Such as MapServer, MapGuideOS, GeoServer, and DeeGree
3) Applications Database. Such as PostGIS

GIS maps produced is a projection from the earth surface geometry data with the actual situation in the 2.5 - 3 dimensions into 2-dimensional. Changes in the dimensions of this is done with little distortion, so the results may be achieved is not too much different with the form, distance and the actual area. There are various types of projection from the surface of the earth, roughly spherical flat as a flds cylinder / tube (cylindrical), cone (conical), flat field (zenithal) and composition (arbitrarry). However, the accuracy is close to the projected composition. Projection is obtained through the calculation.

In Indonesia, generally using the projected composition of the WGS-84 (World Geodetic System) and UTM (Universal Transverse Mercator). UTM projection is a projection map, which many in the select and use in the mapping activities in Indonesia because the value of the ideal syarat2 meet with the appropriate form, location and area of Indonesia. UTM projection in the entire surface of the earth is divided over the 60 called by the UTM zone. Each zone is limited by two meridian at 6 ° meridian and have their own midst. For areas of Indonesia is divided into nine zones UTM, starting from the meridian 90 ° with BT to 144 ° with BT limit pararel (latitude) 11 ° to 6 ° LS LU. Thus, starting from the Indonesian region a zone 46 (central meridian 93 ° BT) to zone 54 (central meridian 141 ° BT).

In some GIS software, there are facilities to change the model data vectors into raster data (Rasterization) or otherwise change the model of raster data into the data vectors (Vektorization). This process is usually useful for instance when we will change the contours of a line (raster) into vector or change the regional map vectors into the surface raster. However, this process usually depends on the resolution of the original data.

Dimensional spatial data can be divided in laminer (point or line), 2-dimensional (area), and 2.5 dimensions (with a value of the surface elevation). Building or buildings to include in 3 dimensions.

Advantages of digital data in GIS is as follows:

1) Variation Data Display

Digital data variations have a view that is almost unlimited. Good shape,
color, size lines, symbols and text can be presented in accordance with the wishes
the map. Besides the changes can be done quickly
and reproduced in whatever amount in a short time.

Digital spatial data, when combined with the diintergrasikan or other data
both spatial and non spatial data can generate a new digital spatial.
For example, spatial data type of soil, rainfall, slope, type of rock,
land use systems, land area and height if combined
with table conditions plants can produce the data level
suitability of land for certain crops.

Digital data can be accessed or used together by
several people at once for the different needs analysis.

Digital data is relatively easier to update, using the facilities
editing existing. Unlike the data manually on the map of the analog (print map
paper).

Data used in GIS can be divided into 2 types of data geometry and attribute data.

1) Data geometry (spatial) showed a spatial (RELIGIOUS) an object. This condition is usually obtained with a spatial mencocokan position of the object with the circumstances of fact in the world. The determination of the geometry of a data point by using GPS (Global Positioning Satellite). Geometry data can be in the form of Raster (pixels) or Vector (Polygon / Area / Line / Point).

a) Raster Data is data that didimpan in a checker square (pixels) that form a field. Position pixels are 2 dimensions to the line with the stated-m-n to the column. This data has weaknesses because it takes too much memory and CPU, which require high processing for high when beresolusi as satellite imagery or photos from the air. Usually, this data is obtained through the process of scanning or shooting with a format like JPEG, tiff, BMP, etc..
b) Vector Data is data that is stored on a line or a polygon closed (the area). Polygon or a line formed by connecting the dots of coordinates (x, y) that have similar values. Because they are vectors of this data does not depend on the resolution. Vector Data consume less memory than raster data. Data stored in the form of the model data vectors, the relation between one object with another object is not saved. In order to be processed through the GIS model of this data must be converted to model saves the data correlation between objects, or through the topology.