Geodata as a compound word coming from geography and data. It is a technical term, created for the sake of brevity. No matter how much technical term it is, however, separating the word in its two synthetics we can easily realize what it is about. So geodata in simple words is data which contain spatial information or geographical locations. We usually store these data in GIS software in order to analyze, edit and visualize. Visualizing geodata gives us the ability to create interactive maps with extreme details and applications in many innovations and surveys.
Geodata can be presented in two forms. These are raster and vector data which are referred to spatial information. In this article, we will analyze the usage and the way we visualize vector and raster data on GIS software
Consists of vectors which encompass an area, a road, a house or everything else a map shows, with the
corresponding attribute. More specifically, with the polygon vector which is a two-dimension feature, we can orb an agricultural area, a neighborhood or a forest etc. After delineating with the polygons, we create the attribute table with details such as the name of the neighborhood, for example, the population, and other characteristics, while we can measure perimeter. The line helps us digitize roads usually, or rivers or rails and give names and lengths on the attribute as it only has one dimension. On the other hand, the point feature is useful to depict schools or churches or whatever is shown as a point in a map. It has no dimension, so we can’t have measurements such as length or perimeter but only the name of the point.
contains a grid where each cell consisted of a value, gives an information such as temperature or color and represent the surface. The whole grid results in a map or image. The use of raster geodata in GIS can be divided into 4 categories:
i. Raster as a base map: the background where we are going to work on.
ii. Raster as a surface map: raster geodata represent surfaces that change easily. Elevation values, rainfall, population density etc. can easily be analyzed.
iii. Raster as a thematic map: Thematic maps may show land-cover or suitability for an activity and raster geodata are ideal for this process.
iv. Raster as an attribute of a feature: It is a separate layer which includes a picture or a document or additional information about a feature in a map.
There are many reasons why we should store geodata as a raster such as the simple data structure, the ability for advanced spatial and statistical analysis, uniformly storage of points, lines, polygons, and surfaces, performing fast overlays with complex data sets etc.
To conclude, in GIS the difference between those two categories of geodata relies on the way each of them represents spatial data.
Geovisualisation is a set of tools, techniques and cartographic technologies, supporting the analysis of geodata. This process describes the effort people to place the geodata in a visual context to understand their significance and draw conclusions. Therefore, the emphasis is given on the field of data construction in such a way to become comprehensible. Some of the applications of geovisualisation are in the wildland firefighting, in forestry, in urban planning and generally in environmental studies.
Essentially, geovisualisation gives the opportunity to create a map of a catchment area with all its natural characteristics originated from geodata and combined in layers. An interactive map is the latest evolution of science, the result of the development of geovisualisation, with maps which change colors without human intervention in order to show the progress of different features in an area.
ArcMap toolset of GIS provides tools which offer faster drawing, enhancement of the image, and retention of the statistical dataset. We will see some of them below.
Regarding the vector geodata, the first thing we do is adding a reference layer with valid geographic coordinates on which the above layers will be based, as it is very important for our map to be placed in the right geographic location. Before starting to draw on the layer, we need to define the color and the thickness of the lines to be sure that the schemes will be visible on the map. Furthermore, we proceed with the add line tool which allows us to start drawing paths, rails etc. Lines, however, are not the only elements as there are also points and polygons which can be either in the same vector object or Vector toolset gives us many advantages such as changing modes from draw to stretch in order to remove overshoots, drag the line in another vertex or move a segment to align with the reference layer completing the drawing. we work on the attribute table by inserting information, labels, and colors which is the most important part of visualization.
The process we follow on raster geodata is almost the same with the vectors. The difference relies on the fact that we use raster tools which have the same function with the vector tools and that when we draw on a raster file, the cell values take new values from the line color.
To conclude, raster and vector geodata have crucial meaning for earth’s evolution. Both include geographical and spatial information, helping us visualize, predict and prevent phenomena. They are treated in almost the same way, nevertheless, the result is unique for each of them as well as the conclusions we export.