Loading and Inspecting Spatial Data

Lesson 2 of 8 · GIS Software Fundamentals · Beginner

Loading data into a GIS project is one of the first practical skills you need. Once data is loaded, inspecting it carefully before doing any analysis saves time and prevents errors.

Types of Spatial Data

Vector data represents geographic features as points, lines, or polygons. A library is a point. A road is a line. A park boundary is a polygon. Each feature has a row in an attribute table with descriptive information such as name, category, or area.

Raster data represents the world as a grid of cells, each holding a value. Satellite imagery, elevation models, and land-cover classifications are common raster datasets. Raster data is loaded and displayed differently from vector data, but the inspection principles are similar.

Tabular data with coordinates — such as a CSV file with latitude and longitude columns — can be loaded into GIS software and displayed as points once the coordinate columns are identified correctly.

Common Spatial File Formats

• Shapefile — a widely used vector format consisting of multiple related files (.shp, .dbf, .prj, and others). All component files must stay together.
• GeoJSON — a text-based format for vector data, readable by many tools and easy to share.
• GeoPackage — a modern single-file format that can store multiple vector and raster layers together.
• KML / KMZ — formats associated with Google Earth, sometimes used for sharing simple geographic data.
• CSV with coordinates — tabular data that can be imported as points when latitude and longitude columns are present.

Web map services (WMS, WFS) allow you to load data from a remote server directly into your project. These are useful for background maps and authoritative datasets, but require an internet connection and depend on the service remaining available.

Loading Data

Most GIS software provides a browser or catalogue panel where you can navigate to a file and drag it into your project, or use a dedicated "Add Layer" menu. The exact steps differ by product — search for how to add a layer in your specific software.

When loading a shapefile, navigate to the .shp file. The software will read the associated files automatically, but all component files must be in the same folder.

Inspecting Loaded Data

After loading a layer, check these things before proceeding:

• Does it appear on the map? If not, check whether the layer is visible and whether the coordinate system is recognized.
• Does it appear where expected? A parks layer for Riverton should appear in Riverton, not in the ocean or on another continent.
• How many features does it contain? Open the attribute table and check the record count.
• What fields are present? Review field names and data types.
• Are there missing values? Scroll through the attribute table and look for empty cells.
• What coordinate system is assigned? Check the layer properties for CRS information.
• Is there metadata? If the dataset came with a metadata file or description, read it before interpreting the data.

Practical Example

You load a CSV file of community centres in Riverton. The file has columns named lat and lon. You tell the software which columns represent latitude and longitude, and the points appear on the map. You open the attribute table and find 42 records. Three rows have empty values in the name field. You note this before proceeding — those records may need follow-up.

Common Mistakes

• Moving or renaming source files after loading them, which breaks the project reference.
• Loading a shapefile by opening only the .shp file while the other component files are in a different folder.
• Assuming that data displaying on the map is correct and complete.
• Skipping metadata, which can explain important limitations or conditions of use.
• Confusing latitude and longitude columns when importing CSV data — swapping them places points in the wrong hemisphere.

Key Takeaways

• Vector data uses points, lines, and polygons; raster data uses grids of values.
• Common formats include shapefiles, GeoJSON, GeoPackage, KML, and CSV with coordinates.
• A shapefile consists of multiple files that must stay together.
• After loading data, inspect its location, record count, fields, missing values, and coordinate system.
• Displaying on the map does not confirm that data is correct.