Term

Description

Bearing

The acute angle generated by the target direction and the meridian, or the acute angle generated by the north or south. For instance,  20° north by east  is N20°E, 30° south by west is S30°W.

Cell

A method to store, handle and display the spatial data. Each given region is split into regular cells in rows. The cell must be rectangle. Each cell in the array contains attributes and location coordinates and the spatial location information is implicit in the order of array; however, the vector structure exactly saves the topology in. In raster structure, the zones of the same attribute value can be considered as the region of same attribute only and the their boundaries can not be identified as polygon. Because each cell in an array will be saved, including features or no-data, the storage of raster structure will occupy much more capacity in some cases.    

Cell Code

Equal to “attribute value”, but not “attribute code.”

Classification

A method to generalize data. It reduces the number of data elements based on the common features and classifies data into groups. The basis of classification is often the attribute or property of data instead of geometric features.

NoData/NULL Value

No data is recorded, particularly refers to the fields of the database table. If no data is recorded in a table field, it means the field doest not store any value. It is different from 0.

Raster Data

To display the spatial data of real world in cells or cell matrix. The spatial location is indicated in the order of cells. In the raster model, the spatial data is not a successive unit but some discontinuous units, so that it is suitable for doing some geoprocessing. For instance, the calculation of iteration or area. However, different from vector data, raster data does not implicit topology.

Raster Data Structures

A kind of spatial data structure. Raster is the basic unit to display the spatial information. Raster data does not has specific specification to represent point, line and polygon.

Raster Databases

The database that saves spatial data in raster format.

Raster to Vector Conversion

Transform the imagery composed by raster cells to feature class data. This might involve topology coding.

Rasterization

Transform the feature class data into raster data. Feature class data is composed by a series of points, lines and polygons. While raster data is a series of cells that have values for each one.

Spatial Analysis

The analyzing technologies related to geographical phenomenon location, spatial relation and attribute study, suitable for evaluation, estimation, explaining and understanding the location and distribution of geographical features and phenomenon.

Spatial Modeling

The analyzing procedures in GIS. It has some spatial modeling types:

1.Geometry modeling: like calculating the geometric distance, area, perimeter and buffer.

2.Spatial Co-existence modeling: like iteration.

3.Neighbor modeling: like searching route, reclassification and allocation.

Vector

A data type to store the spatial data. Vector is composed by line or arc defined by the start and end vertex. The location and topology structure of the vertex are often saved definitely in vector. Features are defined by the boundary only. Vector contains definite topology relationship, and it only saves the feature-related part of information but not includes the space outside the feature.

Vector Data

Vector data describes the location data in coordinates. In vector data, the basic elements including point, line and polygon. Each basic element is composed by a series of single or multiple coordinate points. For instance, a line is the union of points and a polygon is the union of lines. Vector data might have or not have topology.

Vector Data Structures

One of the spatial data structures, the spatial data is represented in vector. The basic elements in vector data structure are point and line and make into arc or polygon.

Vector Displays and Databases

The database of all features is created by points. Line is composed by a series of points and polygon is composed by a closed line.

Vector to Raster Conversion

The process to transform the vector data to raster data. Vector data is composed by a series of points, lines and polygons; the raster data is composed by a series of cells that have their own values.

Vectorization

The process to transform raster to vector. It is a way to reduce  cost on obtaining data and increases the usability of data. For instance, we can vectorization the remote imagery to reduce the mapping cost. The vectorization can be semi-automated or automated. But automated vectorization still has many troubles.