🎯 Learning Objectives
- Differentiate between Geographic (GCS) and Projected (PCS) coordinate systems.
- Identify the correct EPSG code for a specific region (e.g., Texas State Plane).
- Perform a permanent "Project" operation to transform data from WGS84 to NAD83.
- Visualize distortion using the Interactive Projection Explorer.
🧪 Interactive Tool: The Projection Explorer
Before opening your GIS software, use this tool to visualize how different projections distort the size and shape of continents.
📂 Scenario: The Texas Measurement Problem
You are a GIS Technician for the Texas Department of Transportation (TxDOT). You receive a shapefile of road incidents in WGS 1984 (Latitude/Longitude). Your boss asks you to calculate the total length of road repairs needed in Feet.
lab02_projections_data.zip
Contains: tx_roads.geojson (WGS84), tx_counties.shp (NAD83)
🛠️ Step-by-Step Instructions
Select your preferred GIS platform to view instructions:
Check the Coordinate System
1. Add tx_roads.geojson to the map.
2. Right-click the layer in the Contents pane > Properties > Source.
3. Expand Spatial Reference. Note that it says "GCS_WGS_1984". This is unprojected.
Set the Map Frame CRS
1. Right-click "Map" in the Contents pane > Properties > Coordinate Systems.
2. Search for 4203 (NAD 1983 Texas Centric Mapping System Albers).
3. Click OK. Notice how the map "warps" to appear flatter? This is "On-the-fly" projection.
Permanent Projection
1. Open the Geoprocessing Pane.
2. Search for the Project tool (Data Management).
3. Input Dataset: tx_roads
4. Output Dataset: tx_roads_projected
5. Output Coordinate System: Select your "Current Map" (Texas Centric).
6. Run the tool. The new layer is now permanently in feet.
✅ Submission & Assessment
To complete this lab, you must submit:
- Screenshot: The "Properties" window showing your NEW Projected Layer with the correct Coordinate System (Texas Centric).
- Answer: Why did the shape of Texas change when you switched from WGS84 to the Texas projection?