5 Key Spatial Concepts and Terminologies
In this section, we will clarify some important concepts and terminologies that have appeared throughout the tutorial. Understanding these terms is crucial for working effectively with spatial data.
5.0.1 1. Vector Data
Definition: Vector data represents geographic features as discrete shapes, including:
-
Points: Specific locations (e.g., observation sites or cities).
-
Lines: Connected points forming linear features (e.g., roads or rivers).
- Polygons: Closed areas (e.g., country borders or lakes).
| Vector Type | Example | Usage |
|---|---|---|
| Points | Locations of species | Species occurrence data |
| Lines | Roads, rivers | Mapping transport or water networks |
| Polygons | Forest boundaries | Land cover or administrative areas |
5.0.2 2. Raster Data
Definition: Raster data represents the world as a grid of equally sized cells, where each cell holds a value representing a specific attribute (e.g., temperature, elevation).
| Property | Description |
|---|---|
| Resolution | Size of each cell (e.g., 1 km or 10 m). |
| Extent | Geographic area covered by the raster. |
| Values | Data stored in each cell (e.g., temperature). |
5.0.3 3. Coordinate Reference System (CRS)
Definition: A CRS defines how spatial data is projected onto a flat surface, ensuring that different datasets align correctly.
| Type | Description |
|---|---|
| Geographic CRS | Based on latitude and longitude (e.g., WGS84). |
| Projected CRS | Converts the Earth’s surface to a flat map (e.g., UTM). |
- Why CRS matters: Without a common CRS, spatial layers will not align properly, leading to inaccurate analysis.
5.0.4 4. WorldClim Bioclimatic Variables
Definition: WorldClim provides high-resolution climate data used in environmental and ecological modeling. The bioclimatic variables summarize annual trends, seasonality, and extreme or limiting environmental factors.
| Variable | Description |
|---|---|
| Bio1 | Annual Mean Temperature |
| Bio12 | Annual Precipitation |
| Bio4 | Temperature Seasonality (Standard Deviation) |
| Bio15 | Precipitation Seasonality (Coefficient of Variation) |
5.0.5 5. Species Distribution Modeling (SDM)
Definition: SDM is a method used to predict the potential distribution of species based on environmental conditions and known occurrence data.
| Component | Description |
|---|---|
| Environmental Data | Climate and habitat variables influencing species presence. |
| Occurrence Data | Locations where the species has been observed. |
| Modeling Algorithm | Method used to predict species distribution (e.g., MaxEnt). |
5.0.6 6. Global Biodiversity Information Facility (GBIF)
Definition: GBIF is an international network providing access to biodiversity data, including species occurrence records from around the world.
| Term | Description |
|---|---|
| Genus and Species | Taxonomic rank for classifying organisms (e.g., Panthera leo for the African lion). |
| Occurrence Record | A specific instance where a species was observed. |
5.0.7 7. PROJ.4 Strings
Definition: PROJ.4 strings are text representations of CRS parameters used in spatial analysis software.
| Example | Meaning |
|---|---|
+proj=longlat +datum=WGS84 |
Geographic CRS with WGS84 datum. |
+proj=utm +zone=33 +datum=WGS84 |
Projected CRS using UTM Zone 33 with WGS84 datum. |
5.0.8 8. Shapefiles
Definition: A shapefile is a popular file format for storing vector data. It consists of multiple files that together represent geographic features and their attributes.
| File Extension | Purpose |
|---|---|
.shp |
Stores geometry (points, lines, polygons). |
.shx |
Stores index of feature geometry. |
.dbf |
Stores attribute data (tabular data). |
5.0.9 9. GeoTIFF
Definition: GeoTIFF is a raster file format that stores geographic information along with the raster data, making it suitable for spatial analysis.
5.0.10 Key Points to Remember
- Always check the CRS of your spatial data before performing analysis.
- Use appropriate vector or raster data types depending on whether you are working with discrete features (e.g., cities, roads) or continuous surfaces (e.g., temperature, elevation).
- When downloading large datasets (e.g., GBIF or WorldClim), always save them locally to avoid repeated downloads.
If you feel more terms need to be explained or expanded upon, feel free to let me know! 🚀