Geographic Information Systems: A Comprehensive Guide
Working with Database Files: Deleting Fields and Records
Deleting a Field
To delete a field in a database file using forms, follow these steps:
- Open the table and start editing.
- Select the field you want to remove.
- Go to the Edit menu and choose Delete Field.
- Stop editing the table.
Deleting a Record
To delete a record in a database file using forms, follow these steps:
- Open the table and start editing.
- Select the records you want to delete.
- Go to the Edit menu and choose Delete Record.
- Stop editing the table.
Mapping Population Data in Chile
Generating a Population Map by Region
Given an Excel table containing population data by commune for all of Chile and shapefiles (SHP) representing the regions of Chile, you have several options for generating a map of the total population by region:
- **Excel:** Aggregate the population data by region in Excel.
- **ArcView:** Use the Summary command in ArcView. First, select the field representing the region, then select the field representing the commune population. This will summarize the population data by region.
Geocoding by Address
Preparing for Geocoding
After preparing your data for geocoding, the first step is to define and build the structure of the geocoding process to be applied to your data.
Creating a New Theme with Spatial Data
Combining Linear Elements and Administrative Units
To create a new theme containing only linear elements (roads, rivers, railways, pipelines, etc.) within different administrative units, follow these steps:
- Select the linear elements using the external hammer tool.
- Convert the selected elements to a new theme.
Identifying Communes Crossed by Watercourses
To generate a new theme showing only communes crossed by watercourses, use the function that allows you to select sites for linking items and lines through an intersection process.
Dynamic Segmentation
Understanding Dynamic Segmentation
Dynamic segmentation occurs when the initial segmentation process is sufficient to change the positions of line and point events in the relevant databases. As a result, events may move or disappear from the map.
Example
Imagine a map showing traffic flow. As traffic patterns change throughout the day, the positions of vehicles (point events) and traffic flow lines (line events) would dynamically update on the map, reflecting the real-time changes in traffic conditions.
Polyline vs. Polyline M
Polyline
A Polyline is defined as a vector with X and Y coordinates.
Polyline M
A Polyline M is an arc to which the system adds the distance from a source, determined by a file of forms. Therefore, its points are defined as X, Y, M, or X, Y, distance.
Generating a New File with Aggregated Data
Combining Metropolitan, Provincial, and Communal Boundaries
To generate a new file containing only the limits of the metropolitan and provincial boundaries, with all the information present in the communes aggregated for different provinces, use geoprocessing geometric operations with the dissolve option. This allows you to dissolve features while respecting the fields you want to operate on.
Geographic Information: Types and Applications
What is Geographic Information?
Geographic information describes any part of the land surface or items that are on it. This includes not only cartographic and scientific data but also business data, cadastral databases, real estate listings, and more.
Today, over 80% of the data used by businesses and governments relates directly to geographic features.
ArcView Geographic Data Types
Spatial Data
Spatial data forms the core of any application. It consists of geometric elements, along with attribute information describing what these elements represent.
Tabular Data
Tabular data may include any data, whether or not it contains geographic information. Some tables can be viewed directly on a map, while others provide additional attributes that can be joined with existing spatial data.
ArcView Project Data
What is an .APR File?
An .APR file does not contain spatial data or tabular data that you add to your maps. It only stores high-level benchmarks to where you keep the sources of data on disk.
Repairing Project Data
If you cannot find ArcView project data, when you open an existing project, ArcView will check all references to spatial data. If some data is missing, a dialog box will appear asking for the location of the data. This process is called repairing projects.
Defining Item Scale on the Map
By default, ArcView traces items at the current scale. If certain items appear crowded when zoomed in, you can turn them off from the table. However, this can be tedious if a view has many items and the scale changes frequently. In such cases, you can set the display property for these items to control their appearance at different scales.