Coordinate Systems and Spatial Data Models
In lab 2, ArcGIS was used to learn about coordinate systems, datums, projections, and spatial data models (raster and vector data).
Learning Objectives:
- Managing and previewing data using ArcCatalog
- Understanding coordinate systems and projections
- Compare and contrast spatial data models
- Working with remote sensing imagery
In this lab, I learnt that for all Geographical Information System (GIS) analysis, it is important for all datasets to have the same Geographical Coordinate System and map projection. During GIS analysis, if spatial datasets have different coordinate systems and projections, the data output might be misaligned and referenced improperly. When the data is projected into a different coordinate system, the shape, area, and direction of the data are affected.
To ensure that all data layers have the same datum or coordinate system and map projection, the ‘projection-on-the-fly’ function in ArcMap can be utilised. The ‘projection-on-the-fly’ process allows one to combine layers with different coordinate systems and have them align with each other. Alternatively, the ArcToolbox Project and Transformation commands can also be used. This modifies the data and creates a new version of the data layer with a different coordinate system.
I also worked with remote sensing imagery in this lab. Remote sensing is the process of collecting information about an object or surface from afar. This is done by measuring how much a target absorbs or reflects energy when exposed to an energy source. This is the principle used in satellite imagery, aerial photography, and LiDAR.
In this lab, I used remotely sensed Landsat data for geographic analysis. Landsat is a remote sensing program which uses sunlight as its energy source and measures the response of objects and surfaces on earth.
This is advantageous for geographical analysis with regards to assessing land use and topography. Satellite imagery is also useful in monitoring erosion, assessing wildlife habitats or even changes in environmental landscape after natural disasters.